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WORKS  OF 
PROFESSOR  J.  A.  MANDEL 

PUBLISHED  BY 

JOHN  WILEY  &  SONS,  Inc. 


TRANSLATIONS 
A  Text-book  of  Physiological  Chemistry. 

By  Olof  Hammarsten,  Emeritus  Professor  of  Medi- 
cal and  Physiological  Chemistry  in  the  University 
of  Upsala,  with  the  Collaboration  of  S,  C.  Hedin, 
Professor  of  Medical  and  Physiological  Chemistry 
in  the  University  of  Upsala.  Authorized  translation 
from  the  Author's  enlarged  and  revised  8th  German 
edition,  by  John  A.  Mandel,  Sc.D.,  Professor  of 
Chemistry  in  the  New  York  University  and  Bellevue 
Hospital  Medical  College.  viii+1026  pages.  6  by 
9.      Cloth,  $4.00  net. 

A  Compendium  of  Chemistry,    Including  Qeneral, 
Inorganic,  and  Organic  Chemistry. 

By  Dr.  Carl  Arnold,  Professor  of  Chemistry  in  the 
Royal  Veterinary  School  of  Hannover.  Authorized 
translation  from  the  eleventh  enlarged  and  revised 
German  edition,  by  John  A.  Mandel,  Sc.D.  xii-|- 
627  pages.     5i  by  8.     Cloth.  $3.00  net. 


COMPENDIUM   OF    CHEMISTET 


INCLUDING 


GENERAL,  INORGANIC,  AND  ORGANIC  CHEMISTRY 


BY 

Dr.  GAEL  ARNOLD 

Professor  of  Chemistry  in  the  Royal  Veterinary  School 
of  Hanover 


AUTHORIZED    TRANSLATION  FROM  THE   ELEVENTH  ENLARGED 
AND  REVISED  GERMAN  EDITION 


JOHN  A.  MANDEL,  Sc.D. 

professor  of  Chemistry,  Physics,  and  Physiological  Chemistry  in  the 
University  and  BeOevue  Hospital  Medical  College 


FIRST  EDITION' 

SECOND  THOUSAND 


NEW  YORK 

JOHN  WILEY  &  SONS,  Ii^c. 

London:  CHAPMxVN  &  HALL,  Limited 

1914 


-K 


Copyright,  1904, 

BV 

JOHN  A.  MANDEL 


PRESS     OF 

BRAUNWORTH    &    CO. 

BOOKBINDERS    AND    PRINTERS 

BROOKLYN.    N.    Y. 


PREFACE. 


The  successive  editions  of  Prof.  Carl  Arnold's  "  Kepetitorium  der 
Chemie  "  have  served  during  the  past  twenty  years  as  most  useful 
condensed  statements  of  chemical  knowledge.  The  work  has  had 
a  large  circulation  in  Germany  among  students  and  professional 
chemists.  The  numerous  editions,  each  of  which  has  been  larger  than 
its  predecessors,  attest  both  the  popularity  of  the  work  and  the  care 
with  which  the  author  has  kept  in  touch  with  the  advances  in  chemical 
science.  The  eleventh  and  last  edition  contains  concise  but  clear 
statements  of  the  most  important  theories  and  facts,  especially  in 
the  recently  developed  domain  of  physical  chemistry,  as  well  as  a 
classified  review  of  the  most  important  inorganic  and  organic  com- 
pounds, including  statements  of  the  constitution  and  derivation  of 
these  substances.  A  very  complete  index  forms  a  valuable  feature 
of  the  work  and  renders  its  contents  readily  accessible. 

The  feeling  that  this  work  should  be  within  the  reach  of  American 
chemists  and  students  has  prompted  me  to  undertake  this  translation. 

As  I  have  not  been  able  to  find  an  English  equivalent  of  the  Ger- 
man word  "  Repetitorium,"  I  have  been  obliged  to  make  use  of  the 
word  "  Compendium,"  which  seems  to  express  the  nature  of  the  work. 

J.  A.  M. 

May,  1904. 

V 


CONTENTS. 


PART  FIRST.    GENERAL  CHEMISTRY. 

PAQK 

Introduction 1 

Divisions  of  Chemistry 2 

I.  Stoichiometry 5 

Simple  and  Compound  Substances 5 

Chemical  Processes 6 

Causes  of  Chemical  Change 7 

Weight  and  Volume  Relations  in  Chemical  Reactions 9 

Theory  of  Atoms  and  Molecules 13 

Determination  of  the  Molecular  Weight 14 

Determination  of  the  Atomic  Weight 21 

Symbols,  Formulas,  Equations 24 

Theory  of  Valence 27 

Properties  of  Molecular  Aggregations , 32 

Relations  between  Atomic  Weight  and  Properties  of  the  Elements 54 

II.  Chemical  Affinity '. 58 

Chemical  Mechanics 59 

Thermochemistry 67 

Electrochemistry 74 

Photochemistry 91 


PART  SECOND.     INORGANIC  CHEMISTRY. 

Division  of  the  Elements 95 

Nomenclature 96 

I.  Non-metals 103 

Hydrogen 103 

Oxygen  Group 106 

1.  Oxygen 106 

2.  Sulphur 119 

3.  Selenium 131 

4.  Tellurium 131 

vii 


vm  CONTENTS. 


PAOB 


Halogen  Group 132 

1.  Chlorine *  .*  * .  132 

2.  Bromine , I39 

3.  Iodine ' 142 

4.  Fluorine 144 

Nitrogen  Group 145 

1.  Nitrogen 146 

2.  Phosphorus 161 

3.  Arsenic 170 

4.  Antimony 177 

Argon  Group 182 

1.  Argon '. 182 

2.  Heliimi 182 

Boron 183 

Carbon  Group 185 

•  Carbon 186 

Silicon 193 

II.  Metals 198 

Alkali  Metal  Group. 201 

1.  Potassium 201 

2.  Sodium 209 

3.  Caesium 215 

4.  Rubidium 215 

5.  Lithium 215 

6.  Ammonium 216 

Alkaline  Eartlir-metal  Group 218 

1.  Calcium 219 

2.  Strontium 225 

3.  Barium 226 

Magnesium  Group 227 

1.  Beryllium > 227 

2.  Magnesium 227 

3.  Zinc 230 

4.  Cadmium 232 

Silver  Group 233 

1.  Copper : 233 

2.  Silver 238 

3.  Mercury 242 

Earthy-metal  Group , 247 

1.  Aluminum 248 

2.  Gallium 254 

3.  Indium 254 

4.  Thallium 254 

Tin  Group 255 

1.  Tin 255 

2.  Germanium 25S 

3.  Lead 259 

4.  Titanium 262 

5.  Zirconium 263 

6.  Thorium 263 

Bismuth  Group 263 

1.  Bismuth 263 


CONTENTS.  IX 


PAGE 

2.  Vanadium 265 

3.  Niobium 265 

4.  Tantalum 265 

Chromium  Group 265 

1.  Chromium 266 

2.  Molybdenum 271 

3.  Tungsten 271 

4.  Uranium 272 

Iron  Group 272 

1.  Manganese. 273 

2.  Iron 277 

3.  Cobalt 285 

4.  Nickel 287 

Gold  and  Platinum  Group 288 

1.  Gold 289 

2.  Platinum 292 

3.  Palladium 294 

4.  Iridium 294 

5.  Rhodium 294 

6.  Ruthenium 294 

7.  Osmium 295 


PART  THIRD.     ORGANIC  CHEMISTRY. 

Constitviion 296 

Substitution 299 

Isomerism 300 

Determination  of  the  Composition,  Molecular,  and  Constitutional  For- 
mula   309 

Transformations  and  Decompositions 321 

Classification 326 

I.  Aliphatic  Compounds. 

Constitution 328 

Nomenclature 328 

Classification 339 

Compounds  of  Monovalent  Radicals 339 

1.  Monovalent  Alcohol  Radicals 339 

2.  Saturated  Hydrocarbons 340 

3.  Monohydric  Alcohols 342 

4.  Fatty-acid  Series 344 

5.  Methane  and  its  Derivatives 346 

6.  Ethane  and  its  Derivatives 353 

7.  Propane  and  its  Derivatives 370 

8.  Butane  and  its  Derivatives 372 

9.  Pentane  and  its  Derivatives. 374 

10.  Compounds  with  More  than  Five  Carbon  Atoms 375 

11.  Combinations  with  Metalloids 377 

12.  Metallic  Compounds 381 

Monovalent  Compounds  of  Polyvalent  Radicals .,,,,,,,  382 


CONTENTS. 


Compounds  of  the  Cyanogen  Radical 382 

1.  Compounds  of  Cyanogen  with  Metals 385 

2.  Compounds  of  Cyanogen  with  Alkyls 390 

3.  Compounds  of  Cyanogen  with  Halogens,  etc 391 

Compounds  of  Divalent  Radicals 394 

1.  Divalent  Alcohol  Radicals 394 

2.  Halogen  Compounds  of  the  Alkylenes 396 

3.  Amines  of  the  Alkylenes. 397 

4.  Dihydric  Alcohols 399 

5.  Esters  and  Ethers 400 

6.  Aldehydes  and  Ketones 402 

7.  Oxy-f atty-acid  or  Lactic-acid  Series 403 

8.  Carbonic  Acid  and  its  Derivatives 40S 

9.  Oxalic-acid  Series 420 

10.  Malic  Acid,  Tartaric  Acid,  and  Citric  Acid 426 

Compounds  of  Trivalent  Radicals 431 

1.  Trivalent  Alcohol  Radicals , 431 

2.  Trihydric  Alcohols 432 

3.  Derivatives  of  Trihydric  Alcohols 433 

4.  Monohydric  Compounds  of  Trivalent  Radicals 437 

Compounds  of  Tetravalent  Radicals 441 

1.  Tetravalent  Alcohol  Radicals 441 

2.  Tetrahydric  Alcohols 443 

3.  Derivatives  of  Tetrahydric  Alcohols 443 

Compounds  of  Pentavalent  Radicals 443 

1.  Pentavalent  Alcohol  Radicals 443 

2.  Pentahydric  Alcohols 443 

3.  Derivatives  of  Pentahydric  Alcohols 444 

4.  Monohydric  Compounds  of  Pentavalent  Radicals 444 

Compounds  of  Hexavalent  Radicals 445 

1.  Hexavalent  Alcohol  Radicals 445 

2.  Hexahydric  Alcohols 445 

3.  Derivatives  of  Hexahydric  Alcohols 446 

Compounds  of  Heptavalent  and  Higher  Radicals 447 

1.  Alcohol  Radicals 447 

2.  Alcohols  and  their  Derivatives 447 

Carbohydrate  Group 447 

1.  Monosaccharides 451 

2.  Disaccharides 453 

3.  Trisaccharides 456 

4.  Polysaccharides 456 

II.    ISOCARBOCYCLIC  COMPOUNDS 461 

Constitution < 461 

Substitution 464 

Isomerism 466 

Relationship  between  Isocarbocyclic  and  Aliphatic  Compounds 470 

Nomenclature 471 

Classi^cation 471 

The  most  Important  Isocarbocyclic  Compounds 472 

1.  Hydrocarbons 472 

2.  Phenols 474 

3.  Alcohols 475 


CONTENTS.             '  XI 

PAGB 

4.  Acids 476 

Compounds  with  Six  Carbon  Atoms  United  Together 478 

1.  Benzene  Compounds 478 

2.  Oxy-benzene  Compounds 479 

3.  Amido-benzene  Compounds 483 

4.  Hydrazine  Compounds 486 

Compounds  with  Seven  Carbon  Atoms  United  Together 486 

1 .  Toluene  Compounds 486 

2.  Oxy-toluene  Compounds 491 

Compounds  with  Eight  Carbon  Atoms  United  Together 496 

1.  Dimethyl-benzene  Compounds 496 

2.  Ethyl-benzene  Compounds 498 

Compounds  with  Nine  Carbon  Atoms  United  Together 499 

1.  Trimethyl-benzene  Compounds 499 

2.  AUyl-benzene  Compounds 499 

3.  Propyl-benzene  Compounds 501 

Compounds  with  Tenor  More  Carbon  Atoms  United  Together 502 

Compounds  with  several  Benzene  Rings 504 

1.  Compounds  Containing  Benzene  Rings  Directly  United 504 

2.  Compounds  with  Benzene  Rings  United  by  One  Carbon  Atom. .  505 

3.  Compounds  with  Benzene  Rings  United  by  Several  Carbon 

Atoms 508 

4.  Compounds  with  Benzene  Rings  United  by  Nitrogen  Atoms.  .  .  509 
Compounds  with  Condensed  Benzene  Rings 512 

1.  Naphthalene  Compounds 513 

2.  Anthracene  Compounds 515 

3.  Phenanthrene  Compounds 518 

4.  Indene  and  Fluorene  Compounds 518 

Compounds  of  the  Terpene  Group 518 

Compounds  of  the  Glucoside  Group 526 

Bitter  Principles 529 

Compounds  of  the  Pigment  Group 530 

III.   HeTEROCARBOCYCLIC  COMPOUlSTDS 533 

Constitution : 533 

Relationship  between  Heterocarbocyclic  and  Isocarbocyclic  and  Ali- 
phatic Compounds. 534 

Nomenclature 535 

Classification 536 

Six-membered  Compounds  with  One  other  Atom  in  the  Carbon  Ring.  .  . .  536 

1.  Pyridine  Compounds > 538 

2.  Quinoline  Compounds 539 

3.  Acridine  Compounds 540 

4.  Pyrone  Compounds 541 

Six-membered  Compounds  with  Several  other  Atoms  in  the  Carbon 

Ring 542 

1.  Azine  Compounds 542 

2.  Oxazine  and  Thiazine  Compounds 544 

Five-membered  Compounds  with  One  other  Atom  in  the  Carbon  Ring  .  .  544 

1.  Pyrrol  Compounds .  544 

2.  Benzopyrrol  Compounds 546 

3.  Furane  Compounds 549 

4.  Thiophene  Compounds 550 


xu  CONTENTS. 

PAGB 

Five-memhered  Compounds  with  Several  other  Atoms  in  the  Carbon 

Ring 550 

1.  Azole  Compounds 550 

2.  Oxazole  and  Thiazole  Compounds 552 

Alkaloids 552 

Proteins 560 

Index 573 


PART  FIRST. 

GENERAL  CHEMISTRY. 


INTRODUCTION. 

The  aim  of  the  natural  sciences  is  the  investigation  of  the  objects 
and  processes  of  nature.  They  are  divided  into  the  special  sciences, 
each  of  which  is  devoted  to  a  certain  kingdom  of  nature  or  a  portion 
thereof,  and  the  general  sciences,  which  are  confined  to  no  special 
kingdom  of  nature.  The  general  sciences  are  divided  into  physics 
and  chemistry. 

The  earlier  division  of  the  natural  sciences  into  descriptive  (including 
natural  history,  botany,  zoology,  mineralogy,  and  astronomy)  and  exact 
(including  natural  philosophy,  chemistry,  physics,  and  biology)  is  no 
longer  in  accordance  with  the  conditions,  since  chemistry,  on  the  one  hand, 
as  it  must  also  take  into  consideration  the  external  characteristics  of 
chemical  substances,  is  at  once  a  descriptive  science,  while,  on  the  other 
hand,  botany,  etc.,  since  they  must  investigate  not  only  the  external 
reality  but  also  the  chemical  and  physical  changes  transpiring  within, 
are  exact  as  well  as  descriptive  sciences. 

Matter,  material,  or  substance  may  be  defined  as  anything  which  can 
be  weighed  without  reference  to  its  configuration. 

Body  is  the  name  given  to  anything  having  a  definite  form.  For 
example,  iron,  glass,  and  marble  are  forms  of  matter,  while  a  knife,  a 
drinking-glass,  and  a  marble  statue  are  bodies. 

Chemistry  is  the  science  of  matter,  its  properties  and  its  changes; 
its  foundation  is  the  law  of  the  conservation  of  matter  (p.  10),  which 
states  that  no  loss  of  matter  can  take  place  in  any  chemical  change. 
All  phenomena  which  accompany  an  alteration  of  matter  belong  to 
the  domain  of  chemistry. 

For  example,  sulphur  and  iron  mixed  together  give  an  apparently 
homogeneous,  gray  powder,  in  which,  however,  the  separate  particles 
of  iron  and  sulphur  can  be  detected  with  the  aid  of  a  microscope  and 
can  be  separated  from  each  other  by  a  magnet.  If,  however,  the  mixture 
be  heated,  a  black  mass  is  formed  in  which  no  lack  of  uniformity  can  be 

1 


2  GENERAL   CHEMISTRY. 

noticed  with  the  microscope,  from  which  neither  iron  nor  sulphur  can  be 
separated  by  any  mechanical  treatment,  and  which  no  longer  possesses 
the  properties  of  either  iron  or  sulphur.  The  mixture  obtained  in  the 
first  case  is  called  a  mechanical  mixture,  since  by  a  purely  mechanical 
process  it  is  possible  to  separate  it  into  its  constituents,  while  that  obtained 
m  the  second  case  is  called  a  chemical  compound,  since  it  is  possible  to 
separate  it  into  its  components  only  by  a  chemical  process  and  not  by 
any  mechanical  treatment. 

Physics  is  the  science  of  the  alteration  of  the  state  of  a  body;  its 
foundation  is  the  law  of  the  conservation  of  force  (e.g.  energy) :  "  No 
loss  of  force  (e.g.  energy)  occurs  in  any  physical  process,  but  only 
the  transformation  of  one  form  of  energy  into  another  form."  All 
phenomena  in  which  the  matter  undergoes  no  alteration  in  compo- 
sition belong  to  the  domain  of  physics. 

For  example,  a  rod  of  glass  or  a  piece  of  sulphur  after  being  rubbed 
with  a  cloth  attracts  light  bodies,  a  steel  rod  after  rubbing  with  a  magnet 
attracts  objects  of  iron,  and  ice  is  transformed  by  warming  into  water  and 
then  into  steam,  but  neither  the  glass,  the  sulphur,  the  steel,  nor  the 
water  undergoes  any  change  in  composition. 

The  law  of  the  conservation  of  energy  constitutes  the  first  principle  of 
the  mechanical  theory  of  heat.  The  second  principle  of  this  theory 
applies  particularly  to  the  transformation  of  heat  into  mechanical  energy: 
"Only  when  heat  passes  from  a  warmer  to  a  cooler  body  can  it  be  trans- 
formed into  mechanical  work,  and  indeed  this  is  true  for  only  a  certain 
portion  of  the  heat  which  passes.  That  portion  of  the  heat  energy  which 
can  be  converted  into  work  is  called  the  available  energy." 

Divisions  of  Chemistry. 

A  distinction  is  made  between  pure  chemistry,  which  is  engaged 
with  chemistry  solely  for  its  o^vn  sake,  and  applied  chemistry,  which 
considers  chemistry  in  relation  to  certain  special  interests;  and 
according  to  the  purpose  which  it  serves  it  is  denoted  as  medical, 
pharmaceutical,  technical,  agricultural,  physiological,  etc.,  chemistry. 

Analysis  and  Synthesis.— Analytical  chemistry  or  analysis  serves 
for  the  development  of  pure  and  apphed  chemistry  and  is  employed 
for  the  purpose  of  resolving  the  more  complex  substances  into  simpler 
substances  or  elements  Analytical  chemistry  is  divided  into  quali- 
tative analysis,  by  which  only  the  nature  of  the  components  is 
learned,  and  quantitative  analysis,  which  determines  the  quantities 
by  weight  of  the  various  components  present.  A  further  service  is 
rendered  by  synthetical  chemistry  or  synthesis,  by  which  the  more 
complex  substances  are  built  up  from  the  simpler  substances  or  ele- 
ments.   By  sjTithesis  it  is  possible  to  test  the  results  obtained  by 


INTRODUCTION.  3 

analysis,  and  by  the  preparation  from  simpler  substances  of  more 
complicated  compounds,  occurring  in  nature  or  artificially  produced, 
to  arrive  at  the  mode  of  formation  of  the  latter,  and  thereby  to  dis- 
cover a  method  for  preparing  natural  products. 
Pure  chemistry  is  divided  into: 

1.  General  or  theoretical  chemistry;  this  treats  of  the  laws  governing 
chemical  reactions,  as  well  as  the  theoretical  points  of  view  which 
have  found  recognition  in  chemistry.     It  may  be  divided  into: 

a.  Stoichiometry  {oroixeiov^  a  first  principle,  A erpei^^  a  measure); 
this  treats  of  the  relation  between  the  properties  of  existing  sub- 
stances and  their  composition,  their  atomic  and  molecular  weight 
(p.  13),  and  their  constitution  (p.  29). 

The  designation  stoichiometry,  i.e.,  the  art  of  calculating  chemical 
elements,  originated  from  the  fact  that  this  part  of  general  chemistry 
had  its  beginning  in  the  consideration  of  volume  and  weight  relations  of 
chemical  processes. 

b.  Chemical  affinity;  this  treats  of  the  laws  governing  the  mutual 
chemical  attractions  of  the  elements  under  different  external  influences, 
as  well  as  the  rules  governing  the  formation  and  transformation  of 
chemical  compounds.  The  chief  purpose  of  the  doctrine  of  affinity 
is  to  give  an  explanation  of  the  causes  acting  in  the  changes  which 
matter  may  be  made  to  undergo. 

Chemical  processes  are  always  accompanied  by  physical  changes, 
namely,  by  the  production  or  absorption  of  energy  in  the  form  of  heat, 
electricity,  or  light,  the  quantity  standing  always  in  direct  relation  to 
the  nature  of  the  reacting  substances,  so  that  it  is  possible  to  follow  the 
course  of  a  chemical  reaction  by  physical  methods  of  measurement. 

That  branch  of  general  chemistry  which  employs  the  resources  of 
physics  is  called  physical  chemistry.  Frequently,  however,  the  whole 
of  general  chemistry  is  referred  to  as  physical  chemistry. 

2.  Special  or  systematic  chemistry;  this  treats  of  the  knowledge 
pertainin'>- 1^  ^ennT-ate  chemical  substances  and  classifies  them  accord- 
ing to  general  systems.     It  may  be  divided  into 

a.  Inorganic  chemistry;  this  treats  of  the  elements  (p.  5)  and 
their  compounds  with  the  exception  of  those  of  carbon. 

h.  Organic  chemistry;  this  treats  of  the  compounds  of  carbon. 
Such  great  numbers  of  these  are  known,  and  their  relationships  to 
one  another  are  so  complex,  that  for  practical  reasons  they  are  sepa- 
rated from  the  first  class  and  treated  after  the  other  compounds. 
Only  the  compounds  of  carbon  with  oxygen,  sulphur,  and  the  heavy 


4  GENERAL  CHEMISTRY. 

metals,  because  of  their  peculiar  behavior,  etc.,  are  discussed  under 
inorganic  chemistry. 

Organic  chemistry  was  formerly  restricted  to  the  combustible  com- 
pounds of  the  vegetable  and  animal  organisms,  which  were  beUeved  to 
owe  their  origin  solely  to  vital  processes.  However,  after  the  synthesis 
of  urea  (a  product  of  animal  life)  by  Wohler  in  1828,  the  conclusion  was 
reached  that  similar  laws  applied  to  the  products  of  living  and  inanimate 
nature,  and  that  the  assumption  of  a  special  vital  force  was  without 
foundation.  Since  then  a  great  number  of  organic  products  of  plant 
and  animal  origin  have  been  artificially  prepared  and  also  a  great  number 
of  compounds  closely  related  to  these,  so  that  now  a  classification  into 
organic  and  inorganic  chemistry  according  to  the  older  views  would 
be  quite  impossible. 

Many  solid  organic  substances,  e.g.,  wood,  muscle,  leaves,  etc.,  are 
organized,  i.e.,  they  have  a  characteristic  structure,  the  simplest  form 
of  which  is  the  cell.  The  cell  is  the  result  of  the  vital  process  and  can- 
not be  artificially  produced,  while  it  will  ultimately  be  possible  to  prepare 
the  chemical  constituents,  in  common  with  all  other  organic  substances. 


I.  STOICHIOMETRY. 

Simple  and  Compound  Substances. 

All  existing  substances  can  be  divided  into  compound  and  simple 
substances. 

1.  Complex  substances  or  compounds  can  be  separated  into  two 
or  more  substances  differing  from  one  another  and  from  the  original 
substance,  namely,  into  two  or  more  elements. 

2.  Simple  substances  or  elements  are  those  substances  which,  up 
to  the  present,  have  resisted  all  efforts  to  resolve  them  into  more 
simple  constituents.  When  elements  enter  into  chemical  combina- 
tion their  properties  disappear  entirely  or  partly  and  compounds  with 
new  properties  appear,  the  actual  substance  of  the  elements  them- 
selves remaining  unaltered,  which  is  shown  by  the  fact  that  the  ele- 
ments can  be  again  separated  by  chemical  means,  and  numeri- 
cal quantities  of  the  compound  result  as  the  sum  of  the  numerical 
quantities  of  the  elements  which  have  formed  them  (additive  prop- 
erty, p.  30).  In  spite  of  the  enormous  number  of  compounds  occurring 
on  the  earth,  the  number  of  the  elements  from  which  they  are  built 
up  is  not  great  and  the  compounds  essential  to  mankind  are  formed 
from  only  about  one-half  of  the  known  elements.  At  present  78 
elements  (table,  p.  25)  are  known,  and  in  addition  to  these  8-10 
substances  are  designated  as  elements  which  in  all  probability  are 
mixtures  of  unknown  elements  whose  separation  will  be  possible  by 
the  use  of  improved  methods. 

That  this  small  number  of  elements  can  form  all  known  compounds 
will  be  understood  by  a  consideration  of  the  law  of  multiple  proportions 
(p.  11).     Only  about  a  third  of  the  elements  occur  free  in  nature. 

Certain  elements  are  universally  distributed;  for  example,  oxygen 
is  contained  in  the  air,  in  water,  and  in  the  solid  crust  of  the  earth  in 
such  quantity  that  it  constitutes  nearly  one-half  of  the  weight  of  the 
globe,  while  other  elements,  like  cerium,  lanthanum,  etc.,  appear  only 
in  certain  places  and  in  very  small  quantities.  The  elements  are  very 
unequally  distributed  on  the  earth;  up  to  the  present  7  have  been  found 
in  the  air  and  30  in  the  water  of  the  ocean,  while  all  are  more  or  less 

5 


6  GENERAL  CHEMISTRY, 

widely  scattered  throughout  the  earth's  crust.  The  bulk  of  the  earth's 
crust  (the  crystalline  rocks)  consists  on  the  average  of  only  the  following 
8  elements  in  100  parts,  while  the  other  elements  are  present  only  as 
tenths  or  hundredths  of  a  per  cent. : 

Oxygen,   47.3         Aluminium,  8.2  Calcium,        3.7         Sodium,       2.8 

Silicon,     27.9         Iron,  4.8  Magnesium,  2.8         Potassium,  2.5 

As  shown  by  spectrum  analysis  (p.  46),  the  elements  of  which  the 
earth  is  formed  constitute  also  the  other  heavenly  bodies.  Without 
question,  however,  in  addition  to  the  positively  known  elements  there 
are  others  of  whose  existence  we  are  at  present  entirely  ignorant. 

According  to  geological  hypothesis  the  centre  of  the  earth  is  a  mass 
of  molten  substances,  small  quantities  of  which  escape  to  the  surface 
during  volcanic  eruptions.  Since  the  radius  of  the  earth  is  4000  miles, 
while  the  solid  crust  is  only  about  25  miles  in  thickness,  it  is  possible  that 
elements  exist  in  the  interior  which,  owing  to  their  high  specific  gravity, 
have  not  yet  reached  the  surface;  this  appears  the  more  probable  since 
the  specific  gravity  of  the  globe  itself  is  5.6,  while  that  of  the  crust  is 
only  2.5.  Moreover,  the  periodic  system  of  the  elements  (p.  54)  antici- 
pates the  existence  of  about  18  elements  as  yet  undiscovered. 

Chemical  Processes. 

The  processes  involving  a  change  in  substance  are  called  chemical 
processes  or  transformations,  or,  in  general,  chemical  reactions. 

In  the  restricted  sense  the  name  chemical  reaction  is  applied  to  those 
chemical  processes  which  serve  for  the  identification  of  given  substances, 
and  the  substances  employed  for  the  purpose  of  such  tests  are  called 
reagents. 

Every  element  and  every  compound  can  take  part  in  a  chemical 
reaction,  but  the  abihty  to  do  this  varies  within  wide  limits.  Wliile 
many  compounds  offer  extreme  resistance  to  an  alteration  in  their 
composition,  other  compounds  are  stable  only  under  very  special 
conditions.  The  following  classification  of  chemical  reactions  is 
based  upon  the  final  products: 

1.  If  two  or  more  different  elements  or  substances  unite  to  form 
a  single  new  substance,  this  is  called  a  union  or  a  combination ^  e.g., 
A+B=AB;   AB+CD=ABCD. 

When  an  element  unites  with  a  compound  already  in  existence, 
this  is  called  addition,  e.g.,  A+BC=ABC. 

2.  If  one  element  replaces  another  in  a  compoimd  and  sets  it  free, 
the  process  is  called  substitution,  e.g.,  A+BC=AB+C. 

3.  If  a  compound  is  broken  up  into  simpler  compounds  or  into 
elements,  the  process  is  known  as  decomposition,  e.g.,  AB=A+B; 
ABC=AB+C. 


CHEMICAL  PROCESSES.  7 

If,  when  the  causes  which  promote  the  decomposition  are  removed, 
the  decomposition  products  recombine  to  form  the  original  substance, 
the  decomposition  is  called  dissociation. 

4.  When  compounds  mutually  exchange  certain  of  their  con- 
stituents, the  process  is  known  as  multiple  decomposition  (double, 
treble,  etc.,  decomposition),  e.g.,  AB+CD=AC+BD. 

The  chemical  processes  known  as  condensation,  polymerizatioUf 
allotropic  and  isomeric  transformation  will  be  discussed  later. 

Of  course  several  chemical  processes  can  take  place  simultaneously, 
as  a  result  of  which  the  entire  process  becomes  very  complicated,  and 
the  formation  of  a  compound  is  almost  always  dependent  on  a  previous 
decomposition  of  the  reacting  substances,  and  a  decomposition  with  a 
resulting  combination  of  the  decomposition  products. 

Chemical  reactions  which  lead  to  the  formation  of  compounds  more 
complex  than  the  original  substances  are  called  synthetic  processes,  and 
those  which  lead  to  simpler  compounds  are  called  analytical  processes. 

Causes  of  Chemical  Change. 

The  chief  cause  of  the  combination  of  reacting  substances  is  a 
force  known  as  affinity,  by  which  is  understood  a  force  of  attraction 
acting  between  the  separate  elements,  tending  to  bring  them  together 
and  to  hold  them  combined  in  the  resulting  compound.  The  affinity 
between  various  elements  is  of  different  magnitude,  and  indeed  with 
one  and  the  same  element  varies  greatly  under  different  conditions. 

Chemical  affinity  is  not  identical  with  chemical  energy,  since  the 
former  denotes  the  force  which  causes  the  chemical  work,  while  the  latter 
denotes  the  work  which  is  performed  in  chemical  reactions  by  or  against  the 
force  of  affinity  (and  other  forces  which  are  also  involved).  The  relation  of 
chemical  affinity  to  chemical  energy  is  similar  to  that  of  the  weight  of  a 
body  to  the  work  which  the  body  could  perform  through  the  medium 
of  its  weight;  this  work  depending  both  on  the  weight  of  the  body  and 
on  the  height  through  which  it  falls. 

The  force  of  affinity  differs  from  other  forces,  as,  for  example, 
the  force  of  gravitation  and  magnetism,  in  that  it  does  not  act  at  a 
distance,  for  which  reason  substances  which  are  to  combine  must 
be  brought  into  intimate  contact,  and  accordingly  gases  and  liquids 
react  with  one  another  more  readily  than  solids,  and  the  latter  act 
on  one  another  more  readily  when  powdered  or  amorphous  than 
when  compact  or  crystalline. 

It  is  usually  necessary  to  start  or  to  continuously  support  chemical 
affinity  by  heat,  electricity,  light,  or  mechanical  agitation. 


8  GENERAL  CHEMISTRY. 

Frequently  a  number  of  these  forces  act  at  the  same  time,  heat  being 
almost  always  present.  The  action  of  these  forces,  which  are  indeed 
only  modes  of  motion,  consists  in  imparting  motion  to  the  chemical 
substance  (to  the  atoms,  see  p.  13),  which  not  only  excites  this  to 
enter  into  combination,  but  under  some  circumstances  can  be  so  violent 
as  to  cause  through  the  motion  a  decomposition  of  the  compound  which 
is  formed  at  first. 

Affinity  can,  however,  be  accelerated  or  modified  by  certain 
other  causes,  namely,  through  the  relative  proportions  of  the  reacting 
substances  in  solution,  by  the  degree  of  electrolytic  dissociation,  by 
the  solubility  and  volatility  of  the  products  formed,  and  also  by  the 
circumstance  as  to  whether  the  substances  are  already  extant  or 
whether  they  enter  into  reaction  at  the  moment  of  their  production. 
Affinity  is  also  modified  by  the  presence  of  so-called  catalytic  agents, 
certain  substances  which,  without  undergoing  any  change  them- 
selves, influence  the  course  of  chemical  reactions. 

The  chief  causes  which  operate  to  promote  the  decomposition 
of  complex  substances  into  simpler  ones,  namely,  those  which  tend 
to  reduce  or  counteract  the  force  of  affinity,  are  likewise  heat,  elec- 
tricity, light,  and  mechanical  shock,  since  these  forces  can  so  increase 
the  motion  of  the  particles  of  chemical  substances  that  the  compounds 
break  to  pieces. 

1.  Heat.  In  general  an  increase  of  temperature  up  to  a  certain  limit 
increases  the  combining  power  (affinity)  of  substances;  on  the  other 
hand  heating  beyond  a  certain  degree  causes  the  decomposition  of  com- 
pound substances.  For  example,  if  mercury  is  heated  in  the  air,  it  ex- 
tracts oxygen  from  it  and  is  converted  into  the  red  oxide  of  mercury; 
if  the  latter  is  heated  to  glowing,  however,  it  decomposes  again  into 
mercury  and  oxygen  (see  further  under  Thermochemistry). 

2.  Light  can  cause  both  combination  and  decomposition  (see  further 
under  Photochemistry) . 

3.  Electricity.  The  action  of  the  electric  spark,  through  the  increase 
in  temperature  which  accompanies  it,  can  cause  either  combination  or 
decomposition.  The  electric  current  produces  apparent  decomposition; 
in  reality  its  efTect  is  to  separate  from  one  another  the  products  of  de- 
composition already  set  free  by  other  forces  (see  further  under  Electro- 
chemistry) . 

4.  Mechanical  shock  can  promote  the  combination  of  many  substances, 
but  it  can  also  produce  decomposition  by  destroying  the  structure  of 
many  compounds,  often  with  an  explosion.  In  many  cases,  however, 
the  cause  of  tlie  chemical  change  is  due  directly  to  the  heat  produced  by 
the  mechanical  shock,  or  to  the  more  intimate  contact  due  to  the  jar  and 
pressure. 

5.  Electrolytic  Dissociation  (see  under  Theory  of  the  Ions). 

6.  The  relative  quantities  of  the  reacting  substances  present  often 
exert  a  pronounced  influence  on  the  course  of  the  reaction.     For  example, 


WEIGHT  AND  VOLUME  RELATIONS.  9 

chlorine  sets  bromine  free  from  potassium  bromide  and  forms  potassium 
chloride,  wliile  a  proportionately  large  quantity  of  bromine  sets  chlorine 
free  from  potassium  chloride  and  forms  potassium  bromide.  A  solution 
containing  a  small  quantity  of  an  active  substance  usually  acts  more 
feebly  than  one  containing  a  large  quantity  of  the  active  substance, 
while  in  many  cases  the  weaker  solution  has  no  perceptible  action  what- 
ever. For  example,  copper  is  dissolved  only  by  concentrated  sulphuric 
acid  (see  further  under  Chemical  Mechanics). 

7.  The  influence  of  the  solubility  and  volatility  of  the  resulting  sub- 
stances is  always  very  strong  and  characteristic.  When  brought  together 
in  solution  only  those  substances  combine  which  can  form  insoluble  or 
difficultly  soluble  compounds.  If,  for  example,  acetic  acid  is  added  to 
an  aqueous  solution  of  potassium  carbonate,  there  is  formed  potassium 
acetate,  and  carbon  dioxide  is  set  free;  but  if  carbon  dioxide  is  passed  into 
an  alcoholic  solution  of  potassium  acetate,  potassium  carbonate  and 
free  acetic  acid  are  formed,  since  potassium  carbonate  is  insoluble  in 
alcohol. 

Non-volatile  or  slightly  volatile  substances  at  higher  temperatures 
displace  more  volatile  substances  having  stronger  ability  to  react.  For 
example,  when  silicic  acid  is  fused  with  a  salt  of  sulphuric  acid,  the  weaker 
silicic  acid  displaces  the  stronger  sulphuric  acid,  since  the  former  is  not 
volatile,  while  in  aqueous  solutions  salts  of  silicic  acid  are  decomposed 
by  sulphuric  acid,  silicic  acid  being  set  free. 

8.  Catalytic  Agents.  The  presence  of  smSU  quantities  of  certain 
substances  promotes  or  retards  the  course  of  certain  chemical  reactions 
without  any  apparent  change  taking  place  in  the  substances  themselves. 
Such  substances  are  known  respectively  as  positive  or  negative  catalytic 
agents  or  contact  substances,  and  their  action  is  known  as  catalysis 
or  catalytic  action.  For  example,  phosphorus  or  carbon  do  not  burn 
when  heated  in  absolutely  dry  oxy£en,  and  many  metals  when  placed 
in  contact  with  it  enter  into  no  combination,  but  these  substances  com- 
bine as  soon  as  even  a  trace  of  water  is  present.  Cane-sugar  is  split 
into  two  kinds  of  sugar  by  the  action  of  dilute  acids,  the  acids  themselves 
undergoing  no  alteration.  The  probable  action  of  many  positive  cata- 
Ivtic  agents  is  that  they  first  combine  with  one  substance  and  then  give 
this  up  to  the  other;  i.e.,  the  action  depends  upon  the  formation  of  un- 
stable intermediate  products  (see  further  under  Hydrogen  and  Chloride 
of  Lime).  The  action  of  most  positive  catalvtic  agents  can  be  com- 
pared to  the  action  of  fresh  oil  on  a  clock  which  previously  ran  with 
nmch  friction  and  very  slowly  because  of  old  viscous  oil  on  the  pinions. 

9.  The  Nascent  State  (status  nascens).  Substances  show  an  in- 
creased affinity  at  the  moment  that  they  are  set  free  from  their  compounds; 
for  example,  oxygen  does  not  bleach  vegetable  colors,  but  when  set  free 
from  water  by  chlorine  does  so  instantly  (see  p.  17). 

Weight  and  Volume  Relations  in  Chemical  Reactions. 

The  combination  of  elements  follows  certain  laws  which  are  called 
stoichiometrical  laws.  The  study  of  the  laws  governing  the  com- 
bination of  the  elements  and  their  application  to  chemical  calcular 
tions  is  called  stoichiometry  in  the  restricted  sense  (p.  3). 


10  -  GENERAL  CHEMISTRY, 

1.  Law  of  the  Conservation  of  Matter. 

The  total  weight  of  matter  resulting  from  a  combination  or  decom/* 
position  is  always  equal  to  the  sum  of  the  weights  of  all  the  substances 
taking  part  in  the  reaction. 

Superficial  observation  appears  to  contradict  this  law,  since,  for 
example,  when  a  candle  is  burned,  matter  seems  to  disappear.  How- 
ever, more  careful  investigation  shows  that  when  a  candle  burns, 
gaseous  products  are  formed  which  are  not  directly  perceptible  (carbon 
dioxide  and  water  vapor),  and  that  the  weight  of  these  products 
corresponds  exactly  with  the  weight  of  the  candle  burned  plus  the 
weight  of  the  oxygen  of  the  air  consumed  in  the  combustion. 

2.  The  Law  of  Constant  Proportions. 

The  elements  do  not  combine  with  one  another  to  form  compounds 
in  indefinite,  but  in  absolutely  fixed  and  unalterable,  relative  propor- 
tions by  weight. 

Every  definite  compound  therefore  contains  the  elements  of  which 
it  is  composed  in  absolutely  fixed,  unalterable  proportions  by  weight; 
for  example,  water,  irrespective  of  its  source,  always  consists  of  8  parts 
of  oxygen  and  1.01  parts  of  hydrogen,  common  salt  always  of  23  parts  of 
sodium  and  35.4  parts  of  chlorine. 

If  the  proportions  by  weight  in  which  one  element  combines  with 
others  is  known,  then  the  proportions  by  weight  in  which  the  other  ele- 
ments combine  with  one  another  is  known  also.  The  constancy  of  the 
proportions  by  weight  sharply  distinguish  chemical  compounds  from  mix- 
tures. 

The  constant  combining  proportions  have  been  investigated  for  all 
compounds;  the  values  obtained  from  analysis  or  synthesis  were  first 
calculated  on  the  basis  of  100  parts  of  the  compound,  but  the  attempt 
was  soon  made  to  find  a  simpler  expression  for  these  relations  and  to  bring 
them  into  conformity  with  the  combining  relations  of  all  other  elements. 

This  can  be  accomplished,  for  example,  when  oxygen,  which  com- 
bines with  almost  all  other  elements,  is  taken  as  the  point  of  departure. 
In  order  to  allow  a  comparison  with  the  combining  weights  now  in  use, 
namely,  the  atomic  weights,  the  figures  given  below  are  calculated  on 
the  basis  of  how  much  of  the  different  elements  combines  with  8  parts 
of  oxygen,  rather  than  with  1  part  of  oxvgen. 

Thus  8  parts  of  oxygen  combine  with  1.01  parts  of  hvdrogen  to 
form  water,  with  35.4  parts  of  chlorine  to  form  chlorine  monoxide,  with  13 
parts  of  sulphur,  with  4.68  parts  of  nitrogen  to  form  nitrous  anhydride, 
with  3  parts  of  carbon  to  form  carbon  dioxide,  with  27.5  parts  of  man- 
ganese to  form  manganous  oxide,  with  23  parts  of  sodium  to  form  sodium 
oxide,  with  31.8  parts  of  copper  to  form  cupric  oxide,  with  100  parts  of 
mercury  to  form  mercuric  oxide,  and  with  28  parts  of  iron  to  form 
ferrous  oxide. 

Consequently  1.01  parts  of  hydrogen  will  combine  with  35.4  parts 


WEIGHT  AND  VOLUME  RELATIONS.  11 

of  chlorine,  16  parts  of  sulphur,  4.68  parts  of  nitrogen,  and  3  parts  of 
carbon,  and  further  35.4  parts  of  chlorine  or  16  parts  of  sulphur  will 
combine  with  27.5  parts  of  manganese,  23  parts  of  sodium,  31.8  parts 
of  copper,  and  100  parts  of  mercury,  etc. 

The  proportions  by  weight  in  which  the  elements   enter  into 

combination  are  called  combining    weights  and  since  they  have  the 

same  chemical  values  as  the  proportions  by  weight  in  which  they 

replace  or  displace  one  another  in  chemical  decompositions,  they 

are  also  called  equivalent  weights  (p.  12). 

For  example,  if  a  rod  of  copper  is  placed  in  a  solution  of  mercuric 
chloride  (a  compound  of  100  parts  of  mercury  with  35.4  parts  of  chlorine), 
copper  passes  into  solution  until  all  of  the  mercury  has  separated  out. 
For  every  100  parts  of  mercury  which  separate  it  will  always  be  found 
that  31.8  parts  of  copper  enter  into  combination  with  35.4  parts  of  chlorine. 

3.  Law  of  Multiple  Proportions. 

Many  elements  can  combine  with  one  another  in  more  than  one 
proportion  by  weight,  that  is,  they  can  form  more  than  one  compound,  a 
circumstance  which  appears  to  contradict  the  law  of  constant  propor- 
tions. If,  however,  these  proportions  by  weight  are  examined  more 
closely,  it  is  found  that  they  are  always  a  whole  multiple  of  the  lowest 
quantity  by  weight  of  the  given  element  which  enters  into  combination. 

For  example,  nitrogen  forms  five  compounds  with  oxygen: 
14  (3X4.68)  pts.  N.  with  8  pts.  O.  gives  nitrous  oxide. 

14(3X4.68)    "     "       "     16(2X8)    "      "      "       nitric  oxide. 
14(3X4.68)    "     "       "     24(3X8)    "      "      "       nitrous  anhydride. 
14(3X4.68)    "     "      ''     32(4X8)    "     "     "       nitrogen  dioxide. 
14(3X4.68)    "     "       "     40(5X8)    "     "      "       nitric  anhydride. 

Manganese  and  oxygen  also  form  five  compounds: 
27.5  pts.  Mn.  with     8  pts.  O.  form  manganous  oxide. 

27.5     "      "       "       16  (2X8)    "     "       "      manganese  peroxide. 
55.0*"      "       "      24(3X8)    "     "      "      manganic  oxide. 
82.5 1*'      "       "      32(4X8)    "     "      "      manganous-manganic oxide. 
55.0 1  "      "       "      56(7X8)    "     "      "      permanganic  anhydride. 
♦2X27.5.  1 3X27.5.  1 2X27.5. 

If,  in  a  chemical  process,  the  relative  weights  of  the  reacting  elements 
present  do  not  correspond  to  the  laws  of  constant  or  multiple  propor- 
tions, then  the  excess  of  the  particular  element  remains  uncombined. 

For  example,  if  100  parts  of  copper  are  heated  with  100  parts  of  sulphur 
every  31.8  parts  of  copper  combine  with  16  parts  of  sulphur,  and  accord- 
inglv  100  parts  of  copper  with  50.3  parts  of  sulphur,  then  100  —  50.3  =  49.7 
parts  of  sulphur  will  remain  uncombined,  since  31.8  copper  :  16  sulphur 
=  100  copper  \x  sulphur  (a:  =50.3). 


12  GENERAL  CHEMISTRY. 

The  ability  of  the  elements  to  combine  with  one  another  in  several 
proportions  by  weight,  as  well  as  the  tendency  to  combination  of  the 
smallest  parts  (the  atoms,  p.  13)  of  the  elements,  explains  the  enor- 
mous number  of  compounds. 

4.  Law  of  Simple  Proportions  by  Volume. 

The  combination  of  elements  or  compounds  existing  in  the  form 
of  gases  takes  place  according  to  certain  simple  relations  by  volume: 
The  measured  volume  of  a  gaseous  compound  produced  by  the  combina- 
tion of  two  or  more  gaseous  substances  is  equal  either  to  the  sum  of  the 
volumes  of  its  components  or  else  is  smaller  than  this  in  a  ratio  expressible 
by  whole  numbers  (Gay-Lussac's  law  of  volumes).  If  the  volume  of 
that  gas  which  enters  into  the  reaction  in  the  proportion  of  one 
volume  be  taken  as  unity,  then  the  volume  of  gas  resulting  from 
the  combination  of  elementary  gases  will  occupy  the  space  of  two 
volumes,  irrespective  of  the  variation  of  the  sum  of  the  volumes  of 
the  reacting  gases. 

1  vol.  (1.01  parts)  of  hydrogen +  1  vol.  (35.4  parts)  of  chlorine  give 
2  vols.   (36.41  parts)  of  hydrogen  chloride. 

2  vols.  (2.02  parts)  of  hydrogen +  1  vol.  (16.0  parts)  of  oxygen  give  2 
vols.   (18.02  parts)  of  water  vapor. 

3  vols.  (3.03  parts)  of  hydrogen +  1  vol.  (14.04  parts)  of  nitrogen 
give  2  vols.  (17.07  parts)  of  ammonia  gas. 

4  vols.  (4.04  parts)  of  hydrogen +  1  vol.  (12.0  parts)  of  carbon  give 

2  vols.  (16.04  parts)  of  marsh-gas. 

Since  the  gases,  like  all  other  substances,  can  combine  only  in 
definite  proportions  by  weight,  therefore  the  weights  of  the  volumes 
of  the  combining  gases  must  stand  to  one  another  in  the  same  ratio 
as  the  combining  weights  of  the  elements  which  constitute  the  gases. 

The  combining  or  equivalent  weights  calculated  on  the  basis  of  oxygen 
=  8,  which  were  given  above  as  examples,  were  formerly  used  as  the 
foundation  of  all  chemical  calculations,  but  have  been  abandoned,  since 
under  certain  circumstances  different  combining  weights  were  obtained 
for  one  and  the  same  element  so  that  the  choice  became  optional  and 
uncertainty  resulted.  For  example,  manganous  oxide  consists  of  27.5 
parts  of  manganese  and  8  parts  of  oxygen,  manganic  oxide  of  18.33  parts 
of  manganese  and  8  parts  of  oxygen  (p.  11);  further,  nitrous  anhydride 
of  4.68  parts  of  nitrogen  and  8  parts  of  oxygen,  nitrogen  dioxide  of  3.51 
parts  of  nitrogen  and  8  parts  of  oxygen  (p.  11);    further,  methane  of 

3  parts  of  carbon  and  1.01  parts  of  hydrogen,  ethane  of  4  parts  of  carbon 
and  1.01  parts  of  hvdrogen.  This  variation  in  composition  is  explained 
by  the  law  of  multiple  proportions  (since  27.5  manganese  =  3X9.17  and 
18.33   manganese=  2X9.17;    4.68  nitrogen= 4X1.17  and  3.51    nitrogen 


THEORY  OF  ATOMS  AND  MOLECULES.  13 

=  3X1.17);  but  with  respect  to  the  choice  of  the  combining  weights 
manganese  can  be  taken  either  as  27.5  or  18.33,  nitrogen  as  4.68  or  3.5, 
carbon  as  3  or  4,  etc. 

These   difficulties   were   overcome    by   the  atomic   theory   (Ukewise 
through  the  adoption  of  the  atomic  weights). 


Theory  of  Atoms  and  Molecules. 

The  natural  sciences  first  investigate  the  separate  manifestations 
of  nature,  then  attempt  to  discover  the  natural  laws  which  are  the 
basis  of  these  phenomena,  and  finally  try  to  find  the  causes  (natural 
forces)  which  are  disclosed  by  the  laws  and  phenomena.  Since, 
however,  the  actual  nature  of  things  is  beyond  the  scope  of  human 
intellect,  it  is  necessary  to  assume  certain  suppositions  or  hypotheses, 
on  the  basis  of  which  we  are  able  to  explain  the  separate  phenomena 
and  the  laws  which  produce  them. 

If  an  hypothesis  is  applicable  to  the  greater  number  of  the  ob- 
served phenomena,  it  becomes  a  theory. 

The  laws  of  constant  and  multiple  proportions  are  facts,  but  the 
subsequent  assumption  of  the  existence  of  atoms  and  molecules  is,  on 
the  contrary,  only  a  theory  which,  however,  has  much  apparent  truth, 
since  without  it  not  only  a  great  number  of  chemical  but  also  physical 
phenomena  would  be  entirely  incomprehensible. 

I.  Atoms. 

In  explanation  of  the  fact  that  of  every  element  only  a  definite 
quantity  by  weight  or  a  whole  multiple  of  this  quantity  can  take  part  in 
the  formation  of  a  chemical  compound,  it  is  assumed  that  the  ele- 
ments consist  of  very  small  particles  which  are  mechanically  or 
chemically  not  further  divisible.  These  particles  are  called  atoms 
(^r,  privative  and  Te'^vco^  out).  The  atoms  of  the  same  element  are 
absolutely  alike,  and  also  of  equal  weight  and  size.  The  atoms  of  the 
various  elements  differ  from  one  another  in  weight  and  size.  There 
are  as  many  different  kinds  of  atoms  as  there  are  elements. 

It  is  evident  that  if  the  weight  of  an  atom  of  hydrogen  is  1.01 
and  the  weight  of  an  atom  of  chlorine  is  35.4,  these  two  elements  can 
combine  with  one  another  only  in  these  proportions  by  weight;  and 
further,  that  if  the  weight  of  an  atom  of  oxygen  is  8,  in  a  series  of 
compounds  formed  from  nitrogen  and  oxygen  the  quantities  by 
weight  of  the  latter  will  increase  by  increments  of  8  or  by  multiples 


14  GENERAL  CHEMISTRY. 

of  this  number.     This  likewise  depends  upon  the  indivisibility  of 
the  atoms  (Dal ton's  atomic  theory). 

From  the  foregoing  considerations  it  is  impossible  to  determine  whether 
the  equivalent  weights  or  combining  weights  which  have  been  given  also 
represent  the  atonuc  weights.  For  example,  if  water  consisted  of  1  atom 
of  hydrogen  with  1  atom  of  oxygen,  then  the  atomic  weight  of  hydrogen 
would  be  equal  to  1.01  if  the  atomic  weight  of  oxygen  used  as  the  basis 
is  taken  as  8.  However,  water  can  be  formed  from  2  atoms  of  hydrogen 
and  1  of  oxygen,  in  which  case  the  atomic  weight  of  hydrogen  would 
be  equal  to  one-half  of  its  equivalent  weight,  namely,  0.505.  In  order 
to  settle  questions  of  this  nature  it  is  necessary  to  know  the  further  facts 
underlying  the  determination  of  atomic  weights,  through  which  such 
uncertainties  can  be  avoided. 

2.  Molecules. 

The  chemical  compounds  are  formed  by  the  combination  of 
two  or  more  dissimilar  elements,  and  if  we  imagine  any  chemical 
compound  whatsoever  broken  up  by  mechanical  force  (cutting, 
pounding,  etc.)  into  not  further  divisible,  smallest  particles,  then 
these  smallest  particles  will  always  consist  of  a  group  of  atoms,  which 
can  be  divided  further  only  by  chemical  and  not  by  mechanical 
action.     These  particles  are  called  molecules  {molecula,  small  mass). 

For  example,  a  molecule  of  sodium  chloride  is  a  particle  of  sodium 
chloride  which  is  not  further  divisible  by  mechanical  forces:  if,  how- 
ever, it  is  acted  upon  by  chemical  forces,  then  it  is  further  split  up 
into  a  sodium  particle  and  a  chlorine  particle,  that  is,  its  molecules 
can  be  decomposed  into  an  atom  of  sodium  and  an  atom  of  chlorine. 

In  the  case  of  the  undecomposable  substances,  the  elements,  the 
assumption  might  seem  justified  that  a  molecule  is  likewise  an  atom, 
since  no  further  similar  elementary  components  can  be  separated  by 
the  action  of  chemical  forces  from  the  smallest,  not  further  mechan- 
ically divisible,  elementary  particles;  nevertheless,  for  the  reasons 
first  discussed  on  p.  16,  d,  it  is  necessary  to  distinguish  between  the 
concept  molecule  and  atom. 

Determination  of  the  Molecular  Weight. 

Since  it  is  possible  to  determine  for  the  different  elements  the 
smallest  relative  quantities  by  weight  in  which  they  enter  into  com- 
bination, it  must  also  be  possible  to  determine  the  relative  weights 
of  the  different  molecules,  since  the  weights  of  the  molecules  must 
likewise  stand  in  some  relation  to  one  another. 


J 


DETERMINATION  OF   THE  MOLECULAR  WEIGHT.       15 

From  the  quantitative  chemical  analysis  of  a  compound  it  is  possible 
to  calculate  only  the  relation  in  which  the  separate  atoms  are  present, 
but  the  number  of  the  latter  which  are  present  in  one  molecule  of  the 
compound  must  be  determined  by  special  methods. 

The  most  useful  methods  of  determination  are  of  physical  nature, 

since  these  exclude  question  as  to  the  size  of  the  molecules;   but  in 

many  cases  the  chemical  investigation  also  gives  a  sufficient  indication 

for  decision  (see  Part  III,  Determination  of  the  Molecular  Formula). 

In  general,  substances  have  the  same  molecular  weight  whether  in 
a  gaseous,  liquid,  or  solid  condition,  so  that  it  does  not  generally  seem 
objectionable  to  use  the  substances  in  all  three  states  of  aggregation 
for  determining  their  molecular  weights. 

The  numerically  expressible  properties  of  substances,  i.e.,  the 
specific  gravity,  the  refraction,  dispersion,  and  rotation  of  the  plane 
of  polarized  light,  and  the  heat  of  fusion,  are  calculated  on  the  basis 
of  the  molecular  weight  of  substances  whenever  it  is  desired  to  express 
the  relation  between  the  chemical  composition  and  the  properties  of 
substances.  Concerning  the  further  significance  of  the  molecular 
weight  in  chemistry  see  p.  26  and  42,  h,  and  Isomerism,  Part  III. 

The  absolute  values  of  the  atomic  and  molecular  weights  are 
without  practical  significance  for  chemistry,  but  can  be  approxi- 
mately determined  from  various  physical  phenomena. 

I.  Molecular  Weight  of  Volatile  Substances. 

This,  in  the  case  of  all  substances  which  can  be  converted  unde- 
com posed  into  the  gaseous  form,  can  be  deduced  from  their  gas 
densities  (p.  43)  on  the  basis  of  the  following  considerations: 

a.  According  to  Boyle's  law,*  the  volume  of  all  gases  at  a  constant 
temperature  is  inversely  proportional  to  the  pressure. 

It  follows  as  a  consequence  that  the  pressure  (the  tension)  which 
a  gas  exerts  on  the  surrounding  walls  on  compression  at  a  constant  tem- 
perature must  increase  in  the  same  measure  that  the  volume  is  decreased 
or  proportional  to  the  concentration  of  the  gas.  If  the  volume  is  de- 
creased to  one-half,  the  concentration  of  the  gas  being  accordingly  doubled, 
the  pressure  is  also  doubled. 

h.  Gay-Lussac's  lawf  states  that,  if  the  pressure  remains  constant, 
the  volume  of  all  gases  on  warming  increases  in  the  same  proportion 
for  every  1°.     The  coefficient  of  expansion  is  ^^  or  0.003665,  that 

*  Also  called  Mariotte's  law. 
t  Also  called  Charles'  law. 


16 


GENERAL  CHEMISTRY. 


is  to  say,  for  every  increase  in  temperature  of  1°  C.  the  volume  of 
the  gas  expands  ^f  3  of  its  volume  at  0°  C. 

Consequently  the  pressure  that  a  gas  on  warming  at  constant  volume 
exerts  on  the  surrounding  walls  for  every  1°  increase  in  temperature  must 
increase  ^,^3  of  its  pressure  at  0°  centigrade. 

Both  laws  are  explainable  by 

c.  Avogadro's  hypothesis:  Equal  volumes  of  all  gases  at  the 
same  pressure  and  temperature  contain  an  equal  riumber  of  molecules. 
Therefore  by  a  comparison  of  the  weights  of  equal  volumes  of  differ- 
ent gases  at  the  same  pressure  and  temperature  the  relative  weights 
of  the  molecules  can  be  determined. 

Concerning  the  apparent   deviation  of  many  gases  from  Avogadro's 
hypothesis  see  "Thermochemistry  and  Dissociation." 

d.  The  smallest  particles  of  the  free  elements  consist  generally,  like 
the  compounds,  of  molecules  and  not  of  free  atoms. 

By  Avogadro's  hypothesis  this  can  be  demonstrated  as  follows: 


100 

+ 

100 

C13 

= 

[100 
HCl 

100 
HCl 

1  vol 

+   1  vol. 

2  volumes. 

100 

100 

+ 

100 
0. 

= 

100 
H,0 

100 
H,0 

2  vols. 

+ 

1  vol 

2  volumes. 

100 

100 

100 

+ 

100 

= 

100 
NH3 

100 
NH3 

3  vols. 


+    1  vol. 


2  volumes. 


If  a  certain  volume  of  hydrogen  contains  100  molecules  of  hydro- 
gen, then  an  equal  volume  of  chlorine  contains  the  same  number  of 
chlorine  molecules.  By  the  combination  of  this  1  volume  of  hydrogen 
with  the  1  volume  of  chlorine,  2  volumes  of  hydrogen  chloride  (p.  12) 
are  obtained,  which  consequently  must  contain  200  molecules  of 
hydrogen  chloride.  But  200  molecules  of  hydrogen  chloride  must 
contain  200  atoms  of  hydrogen  and  200  atoms  of  chlorine;  therefore  in 
the  formation  pf  hydrogen  chloride  each  molecule  of  hydrogen  and 
chlorine  has  spHt  into  2  parts,  that  is  to  say,  each  of  the  molecules  of 
hydrogen  and  chlorine  consists  of  2  atoms.  Similarly  1  volume  of 
oxygen  with  hydrogen  furnishes  2  volumes  of  water  vapor,  1  volume 
of  nitrogen  with  hydrogen  2  volumes  of  ammonia-gas,  so  that  here 


DETERMINATION  OF  THE  MOLECULAR  WEIGHT.       17 

also  each  molecule  of  oxygen  or  nitrogen  has  separated  into  two 

parts. 

There  is  much  evidence  to  support  the  theory  that  the  molecules  of 
many  elements  consist  of  a  number  of  atoms  (exceptions,  p.  21),  such 
as  the  existence  of  allotropic  modifications  of  the  elements  (see  Ozone), 
certain  chemically  characteristic  reactions  (see  Hydrogen  Peroxide), 
as  well  as  the  energetic  action  of  the  elements  at  the  moment  that  they 
are  released  from  their  compounds  (p.  9),  which  can  be  explained  in 
the  following  manner:  In  the  free  state  the  atoms  have  already  com- 
bined to  form  molecules  and  their  affinity  is  already  partly  satisfied;  there- 
fore before  an  atom  of  the  free  element  can  enter  into  a  compound,  the 
force  must  first  be  overcome  by  which  it  is  held  in  the  molecule  by  the 
other  atoms.  However,  at  the  moment  that  an  element  is  released 
from  one  of  its  compounds  its  atoms  are  quite  free  and  can  tlien  act 
with  their  entirely  unweakened  affinity  much  more  energetically  upon 
other  molecules  present. 

From  the  foregoing  considerations  it  is  evident  that 
Molecular  weight  is  the  smallest   relative  quantity  by  weight  of  an 
element  or  a  compound  which  appears  in  the  free  condition. 

Atomic  weight  is  the  smallest  relative  quantity  by  weight  of  an 
element  which  is  to  be  found  in  the  molecular  weights  of  any  of  its  com- 
pounds. 

The  atomic  weight  of  an  element  holds  good  only  so  long  as  no  com- 
pound of  it  is  known  which  contains  in  the  molecule  a  still  smaller  quan- 
tity of  the  element  than  that  previously  found. 

In  order  to  ascertain  the  relative  weights  of  atoms  and  molecules  it 
is  before  all  things  necessary  to  select  one  substance  as  a  starting- 
point  of  the  comparison,  as  unit,  and  to  compare  all  other  substances 
with  respect  to  their  atomic  and  molecular  weights  ^vith  this  one  sub- 
stance taken  as  the  standard. 

The  unit  which  has  been  chosen  is  1  volume  of  oxygen  =  1  atom  of 
oxygen  =  16  parts  by  weight  of  oxygen. 

It  might  seem  to  be  the  simplest  plan  to  refer  all  the  quantities  by 
weight  of  the  elements  entering  into  compounds  to  that  element  which 
enters  into  compounds  in  the  smallest  quantities  by  weight,  namely, 
to  hydrogen,  and  as  a  matter  of  fact  hvdrogen  was  for  a  long  time  taken 
as  the  unit  of  the  atomic  weights.  But  since  hydrogen  combines  with 
only  a  few  other  elements  to  form  compounds  which  are  suitable  for 
analysis,  the  relation  of  its  atomic  weight  to  the  atomic  weights  of  the 
other  elements  must  usually  first  be  determined  through  the  medium 
of  oxygen,  so  that  also  formerly  oxygen  really  served  as  the  basis.  This 
makes  no  difference  so  long  as  "the  proportion  H:  0=1: 16  is  held  to  be 
correct,  but  it  has  been  demonstrated  that  it  is  extremely  difficult  to 
accurately  determine  this  relation  since  hydrogen  is  the  lightest  element 
and  therefore  the  accurate  determination  of  its  weight  is  greatly  in- 


18         *  GENERAL  CHEMISTRY. 

fluenced  by  errors  of  observation  and  by  the  small  quantities  of  im- 
purities, which  are  in  practice  very  difficult  to  remove.  In  addition  to 
this  the  proportion  by  weight  in  which  hydrogen  combines  with  oxygen 
is  not  yet  established  with  complete  certainty,  but  as  a  result  of  many 
experiments  it  can  be  assumed  that  H:0==  1:15.88  or  1.088:16  is  ap- 
proximately correct.  If  now  0=16  is  changed  to  0=15.88,  then  the 
numbers  expressing  the  atomic  weights  of  all  the  other  elements  must 
be  altered,  while  by  retaining  0=16  the  only  change  necessary  is  to 
make  H=1..00S  (or  in  round  numbers  1.01).  If,  as  a  result  of  further 
refinements  in  the  methods  of  experiment,  the  ratio  between  hydrogen 
and  oxygen  is  again  demonstrated  to  be  incorrect,  the  only  change  neces- 
sary will  be  that  of  the  atomic  weight  of  hydrogen  and  not  that  of  all 
the  other  elements. 

If  1  atom  of  oxygen  occupies  1  volume,  then  1  molecule  of  oxygen, 
since  it  consists  of  2  atoms  (p.  16),  must  occupy  2  volumes,  and  since 
an  equal  number  of  molecules  are  contained  in  equal  volumes  of  all 
gases,  the  molecule  of  every  gaseous  substance  must  occupy  the  same 
space  as  2  atoms  (  =  32  parts  by  weight  =  2  volumes)  of  oxygen. 

The  molecular  weight  is  therefore  that  number  which  expresses  how 
many  times  lighter  or  heavier  a  molecule  of  an  element  or  a  compound 
is  than  one  molecule  ( =  32  parts  by  weight)  of  oxygen.  The  molecular 
weight  of  a  substance  which  can  be  converted  into  vapor  without 
decomposition  is  therefore  found  by  determining  its  specific  gravity 
(gas  density  p.  43),  that  is,  by  determining  how  much  a  given  volume 
of  its  gas  weighs  when  the  weight  of  an  equal  volume  of  oxygen  is 
taken  as  32  units. 

1  litre  of  oxygen  weighs  1.429  grams  and  1  litre  of  hydrogen  chloride 
weighs  l.,678  grams;  therefore  the  molecular  weight  of  the  latter  is  ob- 
tained from  the  proportion  1.429:32:  :1.678:rc  (x=d6.5).  The  molecular 
weight  of  a  gas  can  also  be  determined  by  multiplying  the  weight  of 
1  litre  by  22.4,  since  32^1.429=22.4.  The  correctness  of  the  molecular 
weight  as  determined  by  the  preceding  method  is  demonstrated  further: 

a.  By  Gay-Lussac's'  law  of  volumes  (p.  12),  which  states  that  the 
volume  of  gas  which  results  from  the  combination  of  elementary  gases 
occupies  the  same  volume  as  2  volumes  =2  atoms  of  oxygen: 

1  vol.  =  l  atom  of  oxygen  with  2  vols,  of  hydrogen  gives  2  vols,  of 
water  vapor; 

1  vol.=  l  atom  of  oxygen  with  2  vols,  of  nitrogen  gives  2  vols,  of 
nitrous  oxide; 

2  vols.  =  2  atoms  of  oxygen  with  1  vol.  of  nitrogen  gives  2  vols,  of 
nitrogen  dioxide; 

2  vols.  =  2  atoms  of  oxygen  with  1  vol.  of  sulphur  gives  2  vols,  of  sul- 
phur dioxide. 

6.  The  smallest  molecular  weight  which  can  be  taken  for  hydrogen 
chloride  is  36.41,  since,  according  to  chemical  analysis,  this  quantity 
contains  1.01  parts  of  hydrogen,  namely,  the  smallest  quantity  by  weight 
of  hydrogen  which  enters  into  combination,  corresponding  to  one  atom 


DETERMINATION  OF  THE  MOLECULAR  WEIGHT.       19 

of  hydrogen.  Likewise  the  smallest  molecular  weight  which  can  be  taken 
for  water  is  18.02,  since  in  this  quantity  there  are  contained  16  parts 
of  oxygen,  namely,  the  smallest  quantity  by  weight  (corresponding  to 
one  atom)  of  oxygen  which  enters  into  combination.  Moreover,  36.41 
parts  of  hydrogen  chloride  and  18.02  parts  of  water  vapor  occupy  the 
same  volume  as  2  volumes,  equal  to  32  parts,  of  oxygen. 

2.  Molecular  Weight  of  Soluble  Substances. 

The  molecular  weight  of  all  substances  which  dissolve  without 
decomposition  can  be  determined  from  their  behavior  in  very  dilute 
solutions.  In  such  solutions  these  substances  act  as  if  they  were 
present  as  gases  in  the  volume  which  is  occupied  by  the  solution, 
so  that  the  laws  governing  gases  apply  also  to  dilute  solutions  if  the 
osmotic  pressure  (a  property  of  dissolved  substances,  p.  47,  6)  is  con- 
sidered instead  of  the  gas  pressure. 

Every  substance  which  is  soluble  without  decomposition  shows, 
in  very  dilute  solutions,  an  osmotic  pressure  which  corresponds  to 
the  gas  pressure  which  it  would  exert  if  it  we  e  contained  as  gas  at 
the  same  temperature  in  a  volume  equal  to  that  of  its  solvent  (van't 
Hoff's  theory). 

a.  The  osmotic  pressure  at  constant  temperature  is  inversely 
proportional  to  the  volume  of  liquid  in  which  a  given  quantity  of 
the  dissolved  substance  is  contained;  the  osmotic  pressure  must 
therefore  be  proportional  to  the  concentration  of  the  solution  (analogy 
to  Boyle's  law,  p.  15). 

h.  On  warming  the  solution,  the  increase  in  the  osmotic  pressure 
is  the  same  for  every  1°,  namely,  ^\^  of  the  osmotic  pressure  at  0°  C. 
(analogy  to  Gay-Lussac's  law,  p.  15). 

c.  Equal  volumes  of  solutions  which,  at  the  same  temperature, 
show  equal  osmotic  pressures,  contain  an  equal  number  of  molecules 
of  the  dissolved  substance  (analogy  to  Avogadro's  law,  p.  16). 

The  osmotic  pressure  can  be  determined  only  with  difficulty, 
but  other  properties  of  dilute  solutions  are  known  whose  magnitudes 
stand  in  a  close  relation  to  the  osmotic  pressure  (p.  47,  h)  and  are 
proportional  to  it,  namely,  the  lowering  of  the  vapor  pressure,  the 
depression  of  the  freezing-point,  and  the  elevation  of  the  boiling-point, 
of  which  the  two  latter  especially  can  be  readily  determined. 

Dilute  solutions  of  different  substances,  which  contain  an  equal 
number  of  molecules  of  the  dissolved  substance  in  equal  quantities 
of  the  same  solvent  (equimolecular  solutions),  have  the  same  osmotic 


20  GENERAL  CHEMISTRY. 

pressure  (are  isotonic:  i'cra?,  equal,  r6i^o^,  tension),  the  same  depres- 
sion of  the  freezing-point,  the  same  lowering  of  the  vapor  pressure, 
and  correspondingly  the  same  elevation  of  the  boiling-point.  The 
molecular  weight  of  a  substance  which  dissolves  without  decompo- 
sition is  therefore  determined  by  dissolving  a  small,  accurately 
weighed  quantity  of  the  substance  in  a  known  quantity  of  a  liquid, 
and  determining  the  osmotic  pressure  or  the  vapor  pressure  or,  what 
is  simpler,  the  freezing-  or  boiling-point.  The  value  thus  obtained 
is  compared  with  that  which  is  obtained  when  a  substance  of  known 
molecular  weight  in  a  corresponding  gram-quantity  is  dissolved  in 
the  same  quantity  of  the  same  liquid. 

For  example,  a  quantity  of  a  substance  of  known  molecular  weight, 
corresponaing  to  its  molecular  weight  when  dissolved  in  1000  grams  of 
benzene  (if  soluble  therein),  will  lower  the  freezhig-point  of  the  solvent  by 
4.9°.  Therefore  if  the  aOuition  of  a  known  quantity  x  of  a  substance  of 
unknown  molecular  weight  to  1000  grams  of  benzene  lowers  ihe  freezing- 
point  9.8°,  the  molecular  weight  of  the  unknown  substance  must  be  equal 
•  to  one-half  of  x,  since  9._:=2X4.9. 

If  the  osmotic  pressure,  etc.,  are  determined  in  aqueous  solutions, 
the  solutions  of  acids,  bases,  and  salts  saow  greater  osmotic  pressures, 
etc.,  than  would  be  expected  from  the  theory,  and  tliereforc  for  the  de- 
termination of  the  molecular  weight  of  tliese  sul)stances  other  solvents 
than  water  (e.g.,  acetic  aciu,  benzene,  pyridine,  etc.)  must  be  employed. 
Concerning  the  cause  of  these  exceptions  see  Theory  of  the  Ions. 

Properties,  like  the  osmotic  pressure,  the  expansion  and  pressure  of 
gases,  which  can  assume  similar  values  for  chemically  comparable  quan- 
tities of  unlike  substances,  are  called  colligative  properties  (colligare, 
to  bind);  these,  in  contradistinction  to  the  additive  properties  (p.  30), 
are  influenced  only  by  the  number  of  the  molecules,  not  by  their  nature 
or  constitution. 

3.  Molecular  Weight  of  Substances  which  are  Volatilized  with  Difficulty. 

The  molecular  weights  of  the  metals  which  come  under  this  class 
are  determined  similarly  to  the  molecular  weights  of  dissolved  sub- 
stances. If  small  equimolecular  quantities  of  other  metals  are 
melted  together  with  larger  and  equal  quantities  of  certain  metals 
(bismuth,  lead,  cadmium,  tin),  the  resulting  products  (alloys)  corre- 
spond to  dilute  solutions  and  show  a  corresponding  equal  lowering 
of  the  melting-point.  Therefore  by  determining  the  melting-point 
of  an  alloy  prepared  from  a  metal  of  unknown  molecular  magnitude, 
its  molecular  weight  can  be  calculated  in  the  manner  described  in  2. 


DETERMINATION  OF   THE  ATOMIC  WEIGHT.  21 

DETERMINATION  OF  THE  ATOMIC  WEIGHT. 

I.  Determination  from  the  Molecular  Weight. 

Since  the  atomic  weight  is  the  smallest  quantity  of  an  element 
that  is  present  in  the  molecular  weight  of  any  of  its  compounds,  it 
is  only  necessary  to  determine,  by  the  analysis  of  all  compounds  of 
the  given  element,  in  which  of  these  compounds  the  smallest  quantity 
by  weight  of  the  element  is  present  in  a  quantity  of  the  compound 
corresponding  to  its  molecular  weight. 

For  example,  the  atomic  weight  of  carbon  was  determined  in  this 
manner:  the  molecular  weight  of  a  compound  of  carbon  with  hydrogen, 
which  is  called  marsh-gas,  is  16.04;  in  16.04  parts  of  this  gas  there  are 
contained  12  parts  of  carbon  and  4.04  parts  of  hydrogen.  The  atomic 
weight  of  carbon  could  be  equal  to  12,  6,  3,  etc.,  that  is,  in  one  molecule 
of  marsh-gas  there  could  be  1,  2,  4,  etc.,  atoms  of  carbon  combined  with 
the  4  atoms  of  hydrogen,  but  since  of  all  the  compounds  of  carbon  which 
have  been  examined  not  a  single  one  of  these  contains  less  than  12  parts 
of  carbon  in  the  molecule,  the  number  12  must  be  taken  as  the  minimum 
or  atomic  weight  of  carbon. 

From  the  assumption  that  a  molecule  of  every  substance  in  a 
gaseous  condition  occupies  the  same  volume  as  2  volumes  =  2  atoms 
of  oxygen,  it  might  be  concluded  that  1  atom  of  any  elementary  gas 
occupies  the  same  volume  as  1  volume  =  1  atom  of  oxygen,  so  that  the 
gas  densities  of  the  elements  would  also  be  their  atomic  weights,  and 
that  by  a  comparison  of  the  weights  of  equal  volumes  of  the  given 
gas  and  of  oxygen  the  relative  weights  of  the  atoms  could  be  deter- 
mined. With  certain  elements,  however,  the  weights  thus  found  do 
not  correspond  to  the  atomic  weights;  for  example,  different  atomic 
weights  are  found  for  sulphur  and  iodine  at  different  temperatures 
(see  Dissociation) ;  moreover,  the  molecular  weight  of  phosphorus  as 
determined  from  its  gas  density  is  124,  that  of  arsenic  300,  and  accord- 
ingly their  atomic  weights  must  be  62  and  150  respectively.  But 
the  minimum  weights  which  have  been  found  by  chemical  analysis 
in  any  of  their  compounds  (i.e.,  in  molecular  quantities  of  phosphine 
and  arsine)  correspond  to  only  31  for  phosphorus  and  75  for  arsenic. 
When  in  a  gaseous  condition  their  molecules  therefore  consist  of  4 
atoms. 

In  the  case  of  metals  the  minimum  weight  which  is  found  in  the 
molecular  weights  of  the  corresponding  compounds  is  of  the  same 


22  GENERAL  CHEMISTRY. 

magnitude  as  the  molecular  weight  (p.  20,  3)  of  the  given  metal. 
Their  molecules  therefore  consist  of  only  1  atom. 

The  monatomicity  of  the  molecules  of  the  metals  can  be  demonstrated 
by  Avogadro's  law,  as  well  as  the  diatomic  character  of  the  molecules 
of  the  non-metals;  for  example,  2  volumes  of  mercury  vapor  and  1  volume 
of  chlorine  gas  give  2  volumes  of  mercurous  chloricle  vapor;  2  volumes 
of  mercury  vapor  and  2  volumes  of  chlorine  give  2  volumes  of  mercuric 
chloride  vapor;  if  the  2  volumes  of  mercury  vapor  contain  200  molecules, 
then  the  2  volumes  of  resulting  mercurous  or  mercuric  chloride  vapor 
must  likewise  contain  200  molecules  (p.  16,  d),  and  therefore  in  the 
chemical  combination  of  the  mercury  no  splitting  up  of  mercury  mole- 
cules can  have  taken  place. 

The  compounds  of  all  metals  in  a  gaseous  condition  occupy  the 
same  space  as  the  vapors  of  the  metals  which  are  contained  in  them, 
for  since  the  molecules  of  the  vaporized  metals  are  not  further  divisible, 
when  they  enter  into  chemical  combination  the  number  of  the  molecules 
and  consequently  the  space  which  they  occupy  cannot  be  increased. 

2.  Determination  from  the  Specific  Heat. 

This  method  depends  upon  a  relation  which  exists  between  the 
atomic  weight  and  the  specific  heat  of  every  solid  element,  and  also 
serves  to  check  the  atomic  weights  found  by  other  methods. 

Specific  heat  is  the  number  of  heat  units  (see  Thermochemistry) 
whicii  it  is  necessary  to  add  to  1  gram  orl  kilogram  of  a  substance  in 
order  to  raise  its  temperature  bv  1°  C.  In  the  case  of  solids  this  quantity 
of  heat  can  be  readilv  determined. 

In  order  to  war  n  equal  quantities  of  two  substances  to  the  same 
temperature  two  different  quantities  of  heat  are  necessary.  Thus,  for 
example,  in  order  to  warm  a  given  quantitv  of  water  to  a  certain  tem- 
perature, a  quantity  of  heat  is  required  which  is  thirty-one  times  as  great 
as  that  which  would  be  required  in  order  to  produce  the  same  increase 
in  temperature  in  a  quantity  of  platinum  of  equal  weight.  The  specific 
heat  of  platinum  is  therefore  only  -^  of  that  of  water,  or  expressed  as  a 
decimal  fraction  0.032.  The  specific  heat  of  one  and  the  same  substance 
varies  according  to  its  state  of  aggregation. 

If  the  specific  heat  of  the  elements  in  the  solid  state  is  calculated 
on  the  basis  of  the  atomic  weight,  instead  of  on  the  basis  of  equal 
quantities,  it  is  found  that  quantities  of  the  elements  taken  in  pro- 
portion to  their  atomic  weights  require  equal  quantities  of  heat  in 
order  to  be  raised  to  the  same  temperature,  or  that  all  elements 
have  the  same  atomic  heat  (law  of  Dulong  and  Petit). 

Beryllium,  germanium,  and  the  solid  non-metals  boron,  carbon, 
phosphorus,  sulphur,  and  silicon  have  the  proper  atomic  heat  only  at 
very  high  temperatures. 


DETERMINATION  OF  THE  ATOMIC  WEIGHT.  23 

The  atomic  heat  is  obtained  by  multiplying  the  specific  heat  {H) 
by  the  atomic  weight  {A). 

Since  1  gram  of  platinum  requires  0.032  heat-units  to  raise  its  tempera- 
ture 1°,  then  the  weight  of  platinum  corresponding  to  its  atomic  weight 
(i.e.,  194.8  grams)  will  require  194.8  times  this  quantity  of  heat,  namely 
194.8X0.032=6.2. 

Since  the  average  atomic  heat  is  6.4  {AxH  =  QA),  the  atomic 
weight  {A)  of  an  element  can  be  found  by  dividing  the  quantity  6.4 
by  the  specific  heat  of  the  element;  for  example,  the  specific  heat 
of  lead  is  0.031,  therefore  its  atomic  weight  is  6.4-^0.031  =206.9. 

The  smallest  quantities  by  weight  of  copper  and  silver  which  com- 
bine with  1  atom  of  oxygen  are  63.6  of  the  former  and  216  of  the  latter. 
Do  these  quantities  represent  one  or  more  atoms?  Since  the  atomic 
heat  of  all  elements  is  equal,  therefore  the  atomic  heat  of  these  elements 
must  correspond  with  the  atomic  heat  of  those  elements  whose  atomic 
weights  have  been  determined  by  other  methods.     For  example : 

Specific     Atomic     Atomic 
Heat.      Weight.      Heat. 

Lead 0.0310X206-9=   6-4 

Copper 0.0951  X  63-6=   6-0 

Silver 0.0570X215.8=12.2 

If  these  atomic  heats  of  copper  and  silver  are  compared  with  those 
of  other  metals,  it  will  be  found  that  copper  has  nearly  the  average  atomic 
heat  6.4,  i.e.,  that  its  atomic  weight  is  correctly  determined,  while 
the  atomic  heat  of  silver  is  twice  as  great.  If  the  atomic  weiglit  of  silver 
is  taken  as  half  the  value,  namely  107.9,  then  the  value  obtained  for  the 
atomic  heat  is  6.1. 

The  atomic  heat  of  the  elements  which  cannot  be  examined  in  the 
solid  state  can  be  calculated  for  this  condition,  since  the  elements  in  their 
solid  compounds  possess  the  same  atomic  heat  as  in  the  solid,  free  con- 
dition. The  molecular  heat  corresponds  to  the  sum  of  the  atomic  heats 
^f  the  elements  which  constitute  the  molecule  (law  of  Neumann-Kopp) . 
For  example: 

So.  Heat.    Mol.  Wt. 
Silver  chloride  (1  atom  silver,  1  atom  chlorine) .  .  .   0  •  0S9   X 143 . 3  =  2 X  6  •  3 
Mercuric  iodide  (1  atom  mercury,  2  atoms  iodine)  0 .  0423  X  453 .9=3X6.3 

3.  Determination  from  Isomorphism. 

Many  substances  which  have  an  analogous  chemical  composition 
i.e.,  a  similar  number  and  arrangement  of  the  atoms  in  the  molecule, 
when  the  number  of  atoms  of  which  they  are  constituted  is  equal, 
possess  the  property  of  appearing  in  the  same  crystalline  form  (Iso- 
morphism). There  are  a  large  number  of  isomorphic  compounds 
known  in  which  different  elements  have  replaced  one  another  in 


24  GENERAL  CHEMISTRY. 

proportions  corresponding  to  their  atomic  weights.  Therefore  it 
is  assumed  that  that  quantity  by  weight  shall  be  considered  as  the 
sought  atomic  weight  of  an  element  which  can  replace  a  quantity  by 
weight  of  another  element  corresponding  to  the  known  atomic  weight 
of  the  latter  in  an  isomorphic  compound  without  the  crystalline 
form  of  the  compound  undergoing  an  alteration. 

For  example,  in  potassium-aluminium  sulphate  the  aluminium 
(27.1  parts)  can  be  replaced  by  chromium  (52.1)  parts  without  alter- 
ing its  crystalUne  form,  and  therefore  the  stated  quantities  by  weight 
stand  to  one  another  in  the  same  ratio  as  their  atomic  weights.  Iso- 
morphism (p.  35)  can  be  of  use  for  proving  the  accuracy  of  atomic 
weights  found  by  other  methods,  but  is  of  secondary  importance 
as  a  separate  method  for  the  determination  of  atomic  weights,  since 
substances  which  are  not  of  analogous  composition  exhibit  isomor- 
phism, etc. 

4.  Determination  from  the  Periodic  System. 

If  a  determined  atomic  weight  does  not  fit  into  the  periodic  system 
(p.  54),  then  the  assumption  is  safe  that  the  atomic  weight  has  been  in- 
correctly determined  and  a  redetermination  is  in  order. 

Symbols,  Formulas,  Equations. 

1.  Chemical  Symbols. 

For  the  sake  of  simplicity  in  chemistry  the  elements  are  denoted 
only  by  the  initial  letters  of  their  names,  but  in  cases  where  the  names 
of  several  elements  begin  with  the  same  letter,  a  second  letter  from 
their  name  is  also  added.  These  symbols  have  also  a  quantitative 
significance  since  they  denote  not  only  the  element  but  also  its  atomic* 
weight. 

2.  Chemical  Formulas. 

The  compounds  formed  by  the  combination  of  elements  are 
denoted  by  placing  together  the  symbols  of  the  elements  of  which 
they  are  constituted,  and  a  combination  of  symbols  of  this  character 
is  called  a  chemical  formula;  for  example,  HCl  represents  hydrogen 
chloride.  If  several  atoms  of  one  element  are  contained  in  the 
molecule  of  the  compound,  this  fact  is  denoted  by  a  small  number 
written  as  a  subscript  of  the  given  S3niibol;  for  example,  HgO  =  water, 
NH3  =  ammonia.  A  large  figure  placed  in  front  of  a  formula  or  a  small 
figure  written  after  a  formula  enclosed  in  brackets  refers  to  the  for- 


J 


SYMBOLS,  FORMULAS  AND  EQUATIONS. 


25 


ELEMENTS    WITH   ATOMIC    WEIGHTS. 


Name. 


Aluminium 

Antimony  (Stibium) 

Argon.. 

Arsenic 

Barium 

Beryllium 

Bisnmth 

Boron. 

Bromine 

Cadmium 

CaBsium 

Calcium 

Carbon. 

Cerium 

Chlorine 

Chromium..  .  ." 

Cobalt.  . 

Copper  (Cuprum). .  . 

Erbium 

Fluorine.  ■ 

Gadolinium 

Gallium 

Germanium. 

Gold  (Aurum) 

Helium 

Hydrogen 

Indium 

Iodine 

Iridium 

Iron  (Ferrum) 

Krypton.  .  .  . 

I^anthanum. 

liead  (Plumbum) .  . . 

liithium. 

Magnesium 

Manganese 

Mercury  (Hydrargyrum) 
Molybdenum. ..... 

Neodymium 


Sym- 

Atomic 

bol. 

Weight.' 

Al 

27.1  ! 

Sb 

120.2  ! 

A 

39.9  I 

As 

75.0 

Ba 

137.4 

Be 

9.1 

Bi 

20S .  5 

B 

11.0 

Br 

79. 9C 

Cd 

112.4 

Cs 

132.9 

Ca 

40.1 

C 

12.0 

Ce 

140.25 

CI 

35.45 

Cr 

52.1 

Co 

59.0 

Cu 

63.6 

Er 

166. 0 

F 

19.0    1 

Gd 

156.0    ! 

Ga 

70.0 

Ge 

72.5 

Au 

197.2 

He 

4.0 

H 

1.01 

In 

114.0 

I 

126.85 

Ir 

193.0 

Fe 

55.9 

Kr 

81.8 

La 

138.9 

Pb 

206.9 

Li 

7.03 

Mg 

24.36 

Mn 

55.0 

Hg 

200.0 

Mo 

96.0 

Nd 

143.6 

Name. 


Sym- 
bol. 


Neon 

Nickel 

Niobium 

Nitrogen 

Osmium 

Oxygen 

Palladium 

Phosphorus 

Plathmm 

Potassium  (Kalium) 
Praseodymium ..... 

Radium 

Rhodium 

Rubidium 

Ruthenium. 

Samarium 

Scandium 

Selenium. 

Silicon 

Silver  (Argentum).. . 
Sodium  (Natrium) .  . 

Strontium 

Sulphur 

Tantalum 

Tellurium 

Terbium 

Thallium. 

Thorium 

Thulium 

Tin  (Stannum) 

Titanium 

Tungsten 

Uranium 

Vanadium 

Xenon 

Ytterbium 

Yttrium 

Zinc 

Zirconium 


Ne 

Ni 

Nb 

N 

Os 

O 

Pd 

P 

Pt 

K 

Pr 

Ra 

Rh 

Rb 

Ru 

Sa 

Sc 

Se 

Si 

Ag 

Na 

Sr 

S 

Ta 
Te 
Tb 
Tl 
Th 
Tu 
Si 
Ti 
W 
U 
V 
X 
Yb 
Y 
Zn 
Zr 


Atomic 
Weight. 


20.0 

53.7 

94.0 

14.04 

191.0 

16.0 

106.5 

31.0 

194.8 

39.15 

140.5 

225.0 

103.0 

85.4 

101.7 

150.0 

44.1 

79.2 

28.4 

107.93 

23.05 

87.6 

32.06 

183.0 

127.6 

ICO.O 


204.1 

232.5 

171.0 

119.0 

48.1 

184.0 

238.5 

51.2 

128.0 

173.0 

89.0 

65.4 

90. 6 


mula  taken  as  a  whole  or  to  that  portion  enclosed  in  the  brackets 
only;  for  example,  3H2SO4  or  (HjSOJg  denotes  3  molecules  of  sul- 
phuric acid;  Fcj (80^)3  is  the  formula  for  an  iron  salt  of  sulphuric  acid 
and  indicates  that  this  substance  consists  of  2  atoms  of  iron  and 
3  atomic  complexes  SO4. 

The   formulas   used   express   the   molecular   magnitudes   of   the 


26  GENERAL  CHEMISTRY. 

given  compounds,  as  well  as  the  number  of  atoms  in  the  molecules, 
for  which  reason  they  are  also  called  atomic  molecular  formulas. 
They  give  in  addition  to  the  qualitative  composition  also  the  rela- 
tions by  weight  and  volume  in  which  the  elements  are  present  in 
the  molecules  of  the  compounds. 

If  the  formula  of  a  substance  is  given,  it  is  possible  to  calculate  the 
weight  of  a  liter  of  the  substance  in  a  gaseous  condition,  as  well  as  its 
specific  gravity  with  respect  to  any  other  gas  taken  as  unity  (p.  42,  b), 
and  from  these  quantities  to  further  calculate  its  gram-volume  and 
molecular  volume,  if  only  the  molecular  weight  (  =  32)  and  the  weight 
of  a  liter  (=1.4291)  of  oxygen  are  known.  It  must,  however,  be  borne 
in  mind  that  all  considerations  involving  the  volumes  of  gases  must 
be  based  on  the  volume  occupied  by  gases  under  a  pressure  of  760  mm. 
and  a  temperature  of  0°.  Since  all  specific  gravities  of  gases  are  now 
referred  to  the  molecular  weight  of  oxygen  =  32  as  unit  (p.  43),  their 
specific  gravities  are  therefore  directly  expressed  by  their  molecular 
weights.  The  formula  NHg,  for  example,  consequently  expresses  the  fol- 
lowing concerning  one  molecule  of  ammonia: 

1.  That  it  consists  of  nitrogen  and  hydrogen. 

2.  That  it  consists  of  1  atom=  14.04  parts  of  nitrogen  and  3  atoms 
=  3X1.01  parts  of  hydrogen  and  therefore  has  the  molecular  weight 
17.07. 

3.  That  it  consists  of  1  volume  of  nitrogen  and  3  volumes  of  hydrogen. 

4.  That  it  has  the  specific  gravity  17.07  with  respect  to  oxygen  taken 
as  unit;  further,  that  its  specific  gravity  with  respect  to  hydrogen=l  is 
8.53,  and  with  respect  to  air=l  is  0.59  (see  p.  44). 

5.  That  1  liter  of  it  weighs  0.76  gram,  that  its  molecular  volume  is 
22.4  liters,  and  that  its  gram-volume  is  1.31  liters. 

For  the  basis  of  these  calculations  see  pp.  43,  44. 

In  addition  to  the  empirical  formulas  mentioned  above,  in  which 
only  the  symbols  of  the  elements  constituting  the  molecules  are 
expressed,  there  are  also  the  so-called  rational  formulas  which  indi- 
cate the  grouping  of  the  atoms  in  the  molecules  (p.  29). 

3.  Chemical  Equations. 

This  term  is  applied  to  those  expressions  which  are  used  to  repre- 
sent chemical  reactions  by  the  symbols  and  formulas  of  the  reacting 
substances.  In  these  equations  the  reacting  Substances  are  placed 
on  the  left  (of  the  sign  of  equality)  and  the  resulting  substances  are 
placed  on  the  right.  The  sum  of  the  atoms  of  each  element  on  both 
sides  must  of  course  be  equal,  since  a  chemical  equation  is  at  the 
same  time  an  expression  of  the  principle  of  the  conservation  of  matter 
(p.  10). 


VALENCE.  27 

For  example,  iron  (Fe)  reacts  with  mercuric  sulphide  (IlgS)  to  form 
iron  sulphide  and  mercury.  This  process  can  be  briefly  expressed  as 
follows : 

HgS  +  Fe=FeS  +  Hg, 
which  expresses  that 


Mercuric 

Hg  = 

=  200.3 

232.3 

Fe 

=  32  [^« 

iron 

sulphide 

S     = 

=   32 

S 

sulphide 

and 

+ 

gives 

!    + 

and 

iron 

Fe  = 

=    56 

Hg 

=  200.3 

mercury, 

From  this  equation  it  is  therefore  known  that  for  every  232  parts 
of  mercuric  sulphide  which  are  used  200  parts  of  mercury  will  be  obtained, 
and  that  for  every  232  parts  of  mercuric  sulphide  56  parts  of  iron  must 
be  taken,  which  are  afterwards  obtained  as  88  parts  of  iron  sulphide. 
For  these  reasons  the  study  of  chemical  proportions  is  of  importance 
not  only  for  the  theoretical  development  of  chemistry,  but  for  applied 
chemistry  as  well. 

For  the  sake  of  simplicity,  chemical  equations  are  mostly  written 
in  terms  of  the  atomic  quantities;  but  since  free  elements  enter  into 
reactions  in  molecular  quantities,  it  is  more  in  accord  with  the  facts  to 
employ  only  the  latter  in  equations;  for  example  H2  +  Cl2=2HCl  instead 
of  H  +  C1=HC1.  Equations  are  often  only  the  expression  of  an  ideal 
reaction,  since  many  reactions  do  not  proceed  quantitatively,  Secondary 
reactions  can  take  place  along  with  the  main  reaction  expressed  by  the 
equation,  thus  producing  other  products,  which,  owing  to  the  small  quan- 
tities in  which  they  occur,  can  be  neglected  (see,  for  example,  the  prepara- 
tion of  ethyl  alcohol).  It  is  further  an  important  fact  that  reactions 
proceed  only  to  a  certain  final  state  of  equilibrium  (see  Chemical  Mechanics). 

Theory  of  Valence. 

I.  Valence. 

Although  the  atomic  theory  affords  an  explanation  of  the  law 
of  constant  proportions,  when  applied  to  the  law  of  multiple  pro- 
portions it  merely  serves  to  show  that  the  atoms  can  combine  in 
several  relations.  , 

Nothing,  however,  is  stated  by  the  atomic  theory  as  to  how 
many  compounds  the  same  elements  can  form  with  one  another,  or 
as  to  why  certain  elements  combine  more  readily  in  certain  propor- 
tions than  in  others. 

These  matters  are  explained  by  the  theory  of  valence,  or  atomicity, 
which  attributes  to  every  atom  the  power  of  combining  with  only  a 
perfectly  definite  number  of  atoms  of  every  other  element. 

The  power  which  the  atoms  of  any  element  have  to  combine  with 
the  atoms  of  every  other  element  is  called  the  valence  or  atomicity  of  the 


28  ~  GENERAL  CHEMISTRY    ^ 

element,  and  it  is  measured  by  the  number  of  hydrogen  atoms  with  which 
one  atom  of  the  given  element  can  combine,  or  which  one  atom  of  the 
given  element  can  replace  in  a  compound.  The  valence  of  hydrogen  is 
thus  taken  as  unity. 

If  an  element  does  not  combine  with  hydrogen,  then  its  valence 
is  determined  from  the  number  of  other  atoms,  equivalent  to  an 
atom  of  hydrogen,  with  which  it  can  combine. 

1  atom  of  chlorine  combines  with  1  atom  of  hydrogen  to  form  HCl, 
1      "       "  oxygen  "  "     2  atoms  "  "  "       "     H^O, 

1      "       "  nitrogen  "  "     3       "       "  "  "       "      H3N, 

1      "       "  carbon  "  "     4       "       "  "  "       "     H,C. 

Accordingly  the  valence  of  chlorine  =  1,  of  oxygen  =  2,  of  nitro- 
gen =3,  of  carbon  =4;  and  chlorine  is  thereicro  said  to  be  uni-  or 
monovalent,  oxygen  bi-  or  divalent,  nitrogen  trivalent,  and  carbon 
quadri-  or  tetravalent.  It  is  also  often  customary  to  say  that 
chlorine  possesses  one  and  oxygen  two  bonds  or  units  of  affinity, 
because  it  used  to  be  believed  that  chemical  affinity  (p.  7)  was  con- 
nected with  the  valency. 

The  valence  is  denoted  by  Ptoman  numerals  or  horizontal  dashes 
placed  near  the  symbols  (p.  29). 

The  valence  is  not,  like  the  atomic  weight,  an  inherent  property  of 
the  element,  but  is  dependent  upon  the  properties  of  the  elements  ivhich 
react  upon  one  another.  Every  element  exhibits,  however,  a  maximum 
valence. 


For 

example. 

II 
CO 

III 
PCI3 

III 

II 

SC12 

— 

C120 

— 

IV 
CO2 

V 

PCI5 

V 

P.05 

IV 

IV 

S02 

VI 

S03 

III 

a,03 

V 

VII 

Those  compounds  in  which  an  element  appears  with  a  valence  less 
than  its  maximum  valence  are  called  unsaturated  compounds,  e.g., 
CO,  PCI3,  etc. 

Owing  to  the  variable  valence  of  the  elements,  the  theory  of 
valence  does  not  afford  an  insight  into  all  the  compounds  which 
elements  can  form  with  one  another,  but  nevertheless  a  knowledge 
of  the  maximum  value  is  an  important  assistance  in  approximately 
determining  the  number  of  possible  compounds. 


ATOMIC  LINKING. 


29 


2.  Atomic  Linking. 

As  a  result  of  the  assumption  of  the  valence  for  the  elementary 
atoms,  it  follows  that  the  separate  atoms  in  a  molecule  of  a  chemical 
compound  will  not  be  held  together  by  a  force  exerted  in  common 
by  all  the  other  atoms  present,  but  that  the  force  of  attraction  will 
act  only  from  atom  to  atom,  i.e.,  that  each  atom  will  be  attached  to 
its  neighbors  only. 

Monovalent  atoms  can  be  compared  to  spheres  which  have  only 
one  ring  or  hook  and  can  therefore  be  attached  to  only  one  other 
atomic  sphere;  if  this  second  atomic  sphere  is  likewise  a  monovalent 
atom,  then  no  more  atoms  can  be  attached,  and  there  results  a  satu- 
rated molecule,  the  chain  consisting  of  atomic  spheres  being  a  closed 


one;    for  example,       (h^) — ^ (ci) 


If  the  second  atom  has  a  valence  greater  than  one,  then  only 
one  of  its  valences  will  be  used  in  combining  with  the  monovalent 
atom,  and  the  remainder  can  hold  additional  atoms  and  thus  lengthen 
the  chain  of  atomic  spheres.     For  example, 


-(h)      (^>-^a— 0_a^_^2^_^^— 0 


Water. 


Hydrogen  peroxide. 


The  attachment  of  two  valencies  is  ordinarily  denoted  not  by 
hooks,  but  only  by  a  dash,  thus: 


II  I     IT    I 

H-Cl  H-O-H 

Hydrogen  chloride.       Water. 


I     II     II     I 

H-O-O-H 

Hydrogen  peroxide. 


H 

H-C-H 

I 
H 


H  H 

I     I 

H-C-C-H 

I     I 

H  H 


II  III  II    I 
0=N-0-H 

Nitrous  acid. 

H  H  H  H  H 

III  I     I        /H 

H-C-N-C-H  H-C-C-N< 

II  I     I        \H 

H       H  HH 


Methane,  CH4.         Ethano,C2H6.     Dimethylamine,  NC2H7.     Ethylamine,  NC0H7. 

The  bonding  of  the  atoms  in  molecules  according  to  their  valency 
is  called  the  chemical  constitution  or  structure  of  the  substances. 
The  basis  of  chemical  structure  is  founded  on  the  view  that  every 
valence  of  an  atom  is  attached  to  a  valence  of  some  other  atom. 
The  formulas  constructed  on  this  principle,  which  give  an  idea  as 


30  GENERAL  CHEMISTRY. 

to  the  arrangement  of  the  atoms  in  the  molecules,  are  called  struc^ 
tural  or  constitutional  formulas. 

Structural  formulas,  in  contradistinction  to  empirical  formulas,  are 
called  rational  formulas.  They  are  particularly  indispensable  in  the  case 
of  the  carbon  compounds,  since  there  are  considerable  numbers  of  these 
which,  although  of  similar  qualitative  and  quantitative  composition, 
have  quite  different  properties.     This  is  known  as  isomerism. 

For  example,  the  empirical  formula  NC2H7  stands  for  two  such  com- 
pounds, so  tliat  from  this  it  cannot  be  determined  which  of  the  com- 
pounds is  denoted,  wliile  the  rational  formulas  mentioned  above  make 
it  instantly  possible  to  distinguish  between  them.  The  study  of  chemical 
transformations,  the  different  methods  of  preparation,  and  the  isomerism  of 
organic  compounds  all  lead  to  the  assumption  of  a  definite  arrangement 
of  the  atoms  in  the  molecules  (see  Part  III,  Isomerism  and  Investigation 
of  the  Constitution). 

Tlie  method  of  writing  these  fornmlas  suggests  the  arrangement  of 
the  atoms  in  a  single  plane;  but  since  in  reality  the  separate  molecules 
must  have  definite  volume,  the  separate  atoms  must  be  considered  as 
distributed  through  all  three  dimensions  of  space  (concerning  the  arrange- 
ment of  the  atoms  in  space  see  Part  III,  Stereochemistry). 

The  unvarying  arrangement  of  the  atoms  in  the  molecule  as  a  result 
of  their  linking  does  not  necessitate  that  the  atoms  are  fixed  immovably 
with  respect  to  one  another  in  the  molecule,  but  it  can  be  assumed  that 
notwithstanding  this  they  move  about  a  point  of  equilibrium. 

The  constitution  of  salts  containing  water  of  crystallization  and 
of  other  similar  double  salts  (see  Magnesium  Sulphate)  cannot  be 
explained  by  the  assumption  of  an  additional  valency  belonging  to 
the  atoms,  for  which  reason  it  is  supposed  that  in  these  compounds 
several  molecules  are  present  and  that  these  exert  a  mutual  force 
of  attraction  on  one  another.  Such  compounds  are  therefore  called 
molecular  compounds.     Example,  MgS04,K2S04.6H20. 

Properties  of  substances  which  depend  upon  the  nature  and 
number  of  the  atoms  in  the  molecule  are  called  additive  properties; 
for  example,  the  molecular  weight  is  an  additive  property  since  it 
is  equal  to  the  sum  of  the  weights  of  the  atoms  which  form  the  mole- 
cule. 

Properties  of  substances  which  depend  not  only  on  the  nature 
and  number  of  the  atoms  in  the  molecule,  but  also  on  the  manner 
in  which  the  atoms  are  attached  to  one  another,  are  called  consti- 
tutive properties;  for  example,  the  isomerism  and  the  optical  activity 
of  organic  compounds  are  constitutive  properties.  CoUigative 
properties,  se^  p.  20. 

From  the  foregoing  considerations  it  is  evident  that  chemistry 


.mM, 


I 


EQUIVALENCE.  31 

can  be  defined  as  that  science  wliich  treats  of  the  structure  of  the 
molecule  and  the  investigation  of  the  arrangement  of  the  atoms, 
within  the  molecule,  while  physics  treats  of  the  molecule  as  such 
and  its  properties.  Chemistry  is  the  study  of  equilibrium  and  the 
motion  of  the  aioms  within  the  molecule;  physics,  the  study  of  equi- 
librium and  the  motion  of  the  molecule  itself. 

3.  Equivalence. 

Many  chemical  processes  proceed  in  such  a  manner  that  one 
element  enters  in  the  place  of  another  in  the  molecule  of  a  compound. 
Tills  is  called  substitution  (p.  6).  The  quantities  of  the  elements 
thus  involved  depend  upon  their  valence,  which  in  the  case  of  poly- 
valent elements  denotes  only  a  fraction  of  their  atomic  weight.  But 
since  the  atoms  are  indivisible,  the  substitution  can  only  proceed 
under  such  conditions  that  one  atom  of  a  bivalent  element  replaces 
two  atoms  of  a  univalent  element,  one  atom  of  a  trivalent  replaces 
three  of  a  univalent,  or  one  atom  of  a  bivalent  plus  one  atom  of  a 
univalent.  In  other  words,  the  sums  of  the  atoms  replacing  one 
another  must  be  of  equal  value  (equivalent).     For  example, 

n^H     n^a     ri=o     ri=N     n=o 
^\h     ^\h     ^-h     ^""^     ^=° 

Methane.  Chloroform.       Formaldehyde.  Hydrocyanic  acid.  Carbon  dioxide. 

The  quantities  by  weight  of  the  elements  which  show  equal  values 
(equivalence)  are  called  equivalent  or  substitution  weights,  and  are 
the  fractions  of  the  atomic  weights  corresponding  to  the  valence 
of  the  given  atoms.  Therefore  in  the  case  of  monovalent  elements 
the  equivalent  weights  are  equal  to  the  atomic  weights,  in  the  case 
of  polyvalent  elements  they  are  fractions  of  the  atomic  weights. 

The  equivalent  weight  of  an  element  is  equal  to  its  atomic  weight 
divided  by  its  valence  (with  respect  to  hydrogen  taken  as  the  unit). 

If  chlorine  is  allowed  to  act  on  hvdriodic  or  hydrobromic  acid,  the 
iodine  or  bromine  is  set  free,  and  the  chlorine  combines  with  the  hydrogen, 
viz..  HI  +  Cl-HCl  +  I;    HBr4-Cl=HCl  +  Br. 

One  atom  of  chlorine  (35.4  parts^  replaces  1  atom  of  bromme  (80 
parts)  or  1  atom  of  iodine  (126.8  parts);  and  bromine  also  sets  free  the 
iodine  in  hvdriodic  acid :  HI  +  Br=  HBr  + 1.  The  atoms  of  CI,  Br,  I,  and 
H  have  therefore  the  same  value. 


32  GENERAL  CHEMISTRY. 

Oxygen  also  replaces  iodine  in  hydriodic  acid  and  sets  it  free:  2HI4-0 
=  H20-h2I.  It  is  evident  from  this  equation  that  oxygen  lias  not  the 
same  chemical  value  as  chlorine  and  iodine,  and  that,  as  has  already 
been  observed,  oxygen  is  bivalent,  while  chlorine  and  iodine  are  uni- 
valent. Only  1  ato.n  ( -=  16  parts)  of  oxygen  has  entered  in  place  of  2  atoms 
(=2X123.8  parts)  of  iodine;  therefore  2  atoms  of  iodine  have  the  value 
of  1  atom  of  ox/gea,  or,  since  each  atom  of  iodine^  126.8  parts,  the 
equivalent  quantity  of  oxygen  is  ^  atom=8  parts  of  oxygen. 

One  atom  of  nitrogen^  14.04  parts  is  equivalent  to  3  atoms  (3.03 
parts)  of  hydrogen,  and  therefore  1  atom  (1.01  parts)  of  hydrogen  is  equiv- 
alent to  I  atom  (=4.8^  parts)  of  nitrogen. 

The  combining  weights  employed  on  p.  10  in  explaining  the  laws 
of  constant  and  multiple  proportions  are  identical  with  the  equivalent 
weigiits  discussed  aoov^e,  and  were  formerly  used  in  chemistry  instead 
of  tne  atomic  weights,  iluy  are  still  of  signiiicance  in  electrochemistry 
(under  wnich  see  Faraday  s  Law). 

Properties  of  Molecular  Aggregations. 

Those  masses  of  matter  which  are  capable  of  perception  are 
produced  by  aggregations  of  molecules.  These  aggregations  can 
be  of  different  kinds,  which  determines  the  state  of  aggregation  of 
the  substance,  i.e.,  its  appearance  in  the  solid,  liquid,  or  gaseous 
condition. 

The  alteration  of  the  state  of  aggregation  of  a  substance  is  pro- 
duced, not  by  the  alteration  of  the  state  of  the  molecules  themselves, 
but  through  the  nature  of  the  motion  and  the  alteration  of  the  amount 
of  space  between  them.  It  is  assumed  that  a  certain  amount  of 
space  exists  between  the  separate  molecules,  and  that  in  the  case  of 
gases  this  intermediate  space  is  so  large  that  the  molecules  them- 
selves are  incomparably  small  in  comparison  with  the  space  which 
separates  them.  But  since  the  molecular  weights  of  many  sub- 
stances in  the  same  states  of  aggregation  undergo  an  alteration 
with  a  change  of  temperature  (see  Dissociation),  it  is  not  impossi- 
ble that  at  times  the  alteration  of  the  state  of  aggregation  is  accom- 
panied by  a  change  in  the  size  of  the  molecule.  Usually,  however, 
the  molecular  weights  determined  for  a  substance  in  different  states 
of  aggregation  are  found  to  correspond  with  one  another  (p.  15). 
The  mutual  coherence  of  the  molecules  in  soHd  and  Hquid  substances 
is  produced  by  a  mechanical  force  of  attraction  called  cohesion. 

The  state  of  aggregation  is  dependent  on  the  temperature  and 
pressure.  By  increasing  the  temperature  most  solid  substances 
can  be  liquefied,  and  all  liquids  (Avithin  certain  limits  of  pressure) 
can  be  converted  into  gases;   by  lowering  the  temperature  all  gases 


MOLECULAR  AGGREGATIONS.  33 

can  be  liquefied  and  all  liquids  converted  into  solids.  Many  solid 
substances  cannot  alter  their  state  of  aggregation  by  an  increase 
in  temperature  without  undergoing  a  chemical  decomposition.  By 
a  lowering  of  the  pressure  liquids  can  pass  over  into  gases,  and,  con- 
versely, by  an  increase  in  the  pressure  (within  certain  limits  of  tem- 
perature) gases  can  pass  over  into  liquids. 

The  molecules,  as  well  as  the  atoms  which  compose  them,  are 
considered  as  being  in  a  state  of  constant  vibration.  The  molecules 
of  sohd  substances  vibrate  about  a  point  of  equihbrium,  and  on  warm- 
ing the  vibrations  become  quicker  and  of  greater  amplitude  (expan- 
sion of  warmed  substances),  until  finally  the  cohesion  is  so  far  overcome 
that  it  can  no  longer  retain  the  molecules  in  a  position  of  equilibrium 
and  the  substance  becomes  liquid  (melts).  In  overcoming  the  cohe- 
sion a  certain  quantity  of  heat  is  used  up  (heat  of  fusion),  so  that 
the  melting-point  remains  constant  until  all  is  melted.  If  the  warm- 
ing is  continued,  then  both  on  the  surface  (evaporation)  as  well  as 
within  the  liquid  the  motion  of  the  molecules  will  be  so  increased 
that  the  cohesion  will  be  more  and  more  overcome  and  the  molecules 
will  fly  out  into  the  space  above  the  liquid.  Finally  the  motion 
of  the  molecules  will  become  so  violent  that  they  will  entirely  over- 
come the  pressure  of  the  liquid  and  that  of  the  air  pressing  upon  this 
and  the  liquid  will  begin  to  boil,  whereupon  the  temperature  (boiling- 
point)  will  remain  constant  until  all  is  vaporized,  since  now  all  the 
added  heat  (the  heat  of  vaporization)  is  used  up  in  the  work  of  sever- 
ing the  last  bond  of  the  force  of  cohesion. 

If  heat  acts  still  further  on  completely  gasified  substances,  the 
vibrations  of  the  atoms  in  the  molecules  can  become  so  violent  that 
the  molecules  split  up  into  atoms  or  molecules  of  simpler  constitu- 
tion (dissociation,  see  Thermochemistry). 

I.  Solids. 

These  have  a  characteristic  appearance;  within  them  the  molecules 
move  about  a  fixed  point  of  equilibrium,  vibrating  or  rotating. 

All  solid  substances  occur  organized  (p.  4),  crystallized,  or  amor- 
phous; many  are  known  in  both  the  latter  forms,  but  possess  in  both 
cases  different  physical  properties. 

Very  many  substances,  when  they  pass  from  the  liquid,  dissolved, 
or  gaseous  state  into  the  solid  condition,  assume  a  regular  form  bounded 
by  planes;   i.e.,  they  appear  as  crystals. 

Every  crystallizkble  substance  has  a  perfectly  definite  crystalline 
form   which   can    facilitate    its   identification.     If   it  separates  from  a 


34  GENERAL  CHEMISTRY. 

solution,  the  smallest  crystal  has  the  same  form  as  the  largest,  and  as  they 
grow  in  the  solution  the  forms  of  the  crystals  undergo  no  alteration. 
It  is  very  seldom,  however,  that  the  crystal  form  is  regularly  developed, 
so  that  it  is  very  often  possible  that  in  one  and  the^ame  crystalline  sub- 
stance the  shape  and  development  of  the  separate  planes  can  be  different. 
This  is  never  the  case  with  the  position  of  the  planes  with  respect  to 
the  axes.  The  angles  which  the  planes  of  every  crystallized  substance 
make  with  one  another  are  unalterable  (law  of  the  constancy  of  corre- 
sponding interfacial  angles).  In  addition  to  their  regularly  bounded 
forms,  crystals  possess  a  regular  internal  structure  and  (with  the  ex- 
ception of  those  of  the  regular  system)  exhibit  in  different  directions 
within  them  different  physical  properties  with  respect  to  ccliesion,  hard- 
ness, elasticity,  conductivity  of  heat,  and  the  transmission  of  light. 
Frequently,  especially  on  rapid  cooling,  the  crystals  are  disturbed  in 
their  development  so  that  they  grow  through  one  another  and  a  crystal- 
line body  is  obtained.  The  crystalline  character  of  a  body  is  determined 
by  breaking  it,  after  which  it  can  be  determined  from  the  surface  of  the 
fracture  whether  the  texture  is  laminated,  radiated,  or  granular. 

If  a  substance  shows  no  evidetjce  of  crystalline  structure  and  breaks 
with  a  conchoidal  fracture,  it  is  called  amorphous.  Amorphous  sub- 
stances have  the  same  physical  properties  in  all  directions  within  them, 
and  can  be  compared  to  strongly  supercooled  liquids  (p.  25),  since 
many  substances  can  be  obtained  in  an  amorphous  state  if,  while  in 
the  fused  condition,  they  are  cooled  rapidly.  The  amorphous  state 
is  almost  always  unstable,  and  amorphous  substances  after  standing 
for  some  time  pass  over  spontaneously  into  the  crystalline  condition. 

a.  Crystallogi-aphy. 

The  study  of  crystal  forms  is  called  crystallography.  Many  thousands 
of  crvstal  forms  are  known,  but  they  can  all  be  referred  to  six  classes 
or  systems.  This  can  be  accomplished  by  comparing  the  crystals  ac- 
cording to  their  directions  of  development,  called  axes,  i.e.,  we  imagine 
a  series  of  lines  (axes)  passing  through  the  middle  points  of  the  crystals, 
so  placed  that  the  crystal  faces  lie  symmetrically  about  these  axes.  From 
the  number  of  axes,  their  length  and  inclination,  all  crystals  can  be 
classified  into  six  system.s. 

The  classification  of  all  crystal  forms  of  the  six  systems  can  be  ac- 
complished also  by  the  assumption  of  symmetry  planes  instead  of  axes. 
A  symmetry  plane  denotes  a  plane  which  can  be  imagined  as  so  dividing 
a  crystal  into  two  halves  that  the  one  half  stands  in  the  same  relation 
to  the  other  half  as  the  one  half  stands  to  its  image  as  seen  reflected  in 
a  mirror.  The  differences  between  the  six  crystal  systems  are  therefore 
the  following: 

1.  Regular  or  isometric  system:  3  axes  of  ecfual  length,  all  at  right 
angles  to  one  another. — 9  planes  of  symmetry. 

2.  Quadratic  or  tetragonal  system:  3  axes,  2  of  equal  length,  the 
third  (principal  axis)  longer  or  shorter,  all  at  right  angles  to  one  another. 
—  5  planes  of  symmetry. 

3.  Orthorhombic  or  trimetric  system:  3  axes  of  different  lengths,  all 
at  right  angles  to  one  another. —  3  planes  of  symmetry. 

4.  Monoclinic,  monosymmetric,  or  clinorhombic  system:    3  axes  of 


FUSION  AND   VAPORIZATION.  35 

different  lengths,  2  of  these  at  an  obUque  angle  with  one  another  but 
at  right  angles  to  the  third. —  1  plane  of  symmetry. 

5.  Trichnic,  asymmetric,  or  clmorhumboidal  system:  3  axes  of  dif- 
ferent lengths,  all  forming  oblique  angles  with  one  another. — No  planes 
of  symmetry. 

6.  Hexagonal  system:  4  axes,  3  of  these  of  equal  length  and  cutting 
one  another  at  angles  of  60°,  and'  a  fourth  axis  longer  or  shorter  and 
perpendicular  to  tne  plane  of  the  other  three. —  7  planes  of  symmetry. 

A  compound  whicn  can  appear  in  crystal  forms  belonging  to  more 
than  one  crystal  system  is  called  polymorphic,  namely,  dimorphic, 
trimorphic,  etc.,  according  to  whether  the  forms  belong  to  2,  3,  etc., 
crystal  systems.  In  these  cases  the  diiferent  crystal  forms  always  exhibit 
a  difference  in  their  physical  properties  (calcium  carbonate  as  aragonite 
is  orthorhombic,  as  calcite  hexagonal).  Elements  also  can  exhibit 
polymorphism  (sulphur  appears  both  orthorhombic  and  monoclinic, 
although  this  is  usually  denoted  as  allotropism  (which  see). 

Various  compounds  can  often  have  the  same  crystal  form  and  are 
then  called  isomorphic,  e.g.,  the  carbonates  of  calcium,  magnesium,  zinc, 
manganese,  and  iron.  These  can  form  mixed  crystals  (p.  50)  and 
often  have  a  similar  constitution,  a  fact  which  is  made  use  of  in  the  de- 
termination of  the  atomic  weights  (p.  23). 

6.  Fusion  and  Vaporization. 

Solid  substances  which  can  be  melted  are  called  fusible,  and  when 
they  can  l^e  vaporized  they  are  called  volatile.  Every  solid  substance, 
like  every  liquid,  at  anv  given  temperature  has  a  defmite  vapor  pressure, 
which,  however,  at  ordinary  temperatures  is  generally  very  small.  It 
is  a  fact,  however  that  many  substances  are  volatile  even  at  ordinary 
temperatures.  The  melting-point  is  that  temperature  at  which  a  sub- 
stance becomes  liquid,  and  has  a  fixed  value  for  every  pure  crystalline 
substance  that  melts  without  decomposition.  It  is  therefore  a  charac- 
teristic of  substances  and  is  important  for  determining  their  purity. 
Many  substances  do  not  melt  without  undergoing  decomposition.  Amor- 
phous substances  have  no  definite   melting-point. 

The  melting-point  corresDonds  with  the  freezing-  or  solidifying-point 
of  the  melted  substance.  Many  substances  can  be  cooled  under  favor- 
able conditions  below  their  solidifving-point  without  becoming  solid. 
For  example,  water,  if  protected  from  every  mechanical  disturbance, 
can  be  cooled  below  0°  without  freezing;  on  being  shaken  it  instantly 
changes  into  ice  and  the  temperature  rises  to  the  melting-point  (p.  36). 

Substances  which  under  certain  conditions  remain  melted  at  tem- 
peratures which  are  lower  than  their  normal  points  of  solidification 
are  said  to  be  supercooled  or  superfused  (analogy  to  supersaturated  solu- 
tions, p.  52). 

By  increasing  the  external  pressure  the  melting-points  of  most  sub- 
stances which  melt  with  an  increase  of  volume  is  raised.  In  the  case 
of  ice  and  certain  other  substances  which  undergo  a  reduction  in  volume 
on  melting,  an  increase  in  the  external  pressure  causes  a  lowering  of  the 
melting-point. 

By  a  reduction  of  the  external  pressure  all  fusible  substances  can 

Eass  directly  over  into  the  gaseous  condition,  as  soon  as  the  pressure  has 
ecome  less  than  the  vapor  pressure  of  the  substance  at  its  melting- 


36  GENERAL  CHEMISTRY. 

point.  FoF'example,  ice  melts  at  0°,  and  at  this  temperature  iias  a  vapor 
pressure  of  4.6  mm.  If  the  external  pressure  is  reduced  to  less  than 
4.6  mm.,  the  ice  passes  into  the  form  of  vapor  before  it  reaches  its  melt- 
ing-point. 

Many  solid  substances  (mercurous  chloride,  ammonium  chloride, 
metallic  arsenic,  and  many  carbon  compounds,  on  being  heated  at 
normal  atmospheric  pressure,  vaporize  without  melting,  since  their 
vapor  pressures  at  their  melting-points  are  higher  than  the  atmospheric 
pressure.  If,  therefore,  the  external  pressure  is  increased  until  it  equals 
the  vapor  pressure,  then  these  substances  can  be  melted. 

The  pressure  below  which  many  solid  substances  no  longer  melt, 
but  pass  directly  into  the  form  of  vapor,  is  called  their  sublimation  pres- 
sure. 

The  transformation  of  a  solid  substance  into  vapor  and  the  con- 
densation of  the  vapor  into  the  solid  state  is  called  sublimation;  it  serves 
to  separate  volatile  from  non-volatile  substances.  The  ordinarily  slight 
variations  in  the  atmospheric  pressure  can  be  neglected  in  melting-point 
determinations. 

After  a  substance  has  begun  to  melt,  the  quantity  of  heat  which  is 
added  until  all  is  melted  (the  heat  of  fusion,  p.  33)  does  not  produce 
any  increase  in  the  temperature.  In  like  manner  a  fused  substance 
on  solidification  yields  the  same  quantity  of  heat  which  it  took  up  on 
melting  without  undergoing  any  reduction  in  temperature  (the  heat 
of  solidification). 

The  heat  of  fusion  or  solidification  is  the  number  of  heat-units  (see 
Thermochemistry)  which  are  required  in  order  to  transform  1  gram  or 
1  kilogram  of  a  solid  substance  into  liquid  at  the  same  temperature. 
If  the  heat  of  fusion  is  multiplied  by  the  molecular  weight,  the  molecular 
heat  of  fusion  is  obtained. 

In  regard  to  the  alteration  of  the  melting-point  in  mixtures  of  solid 
substances  see  p.  50.  For  the  relation  of  the  lowering  of  the  melting- 
point  to  the  molecular  weight  see  p.  20,  and  for  the  relation  of  the  melt- 
ing-point to  the  constitution  of  organic  compounds  see  Part  III. 

c.  Specific  Heat. 

of  solid  substances  and  its  relation  to  the  atomic  and  molecular  weight. 
See  p.  22. 

d.  Specifx  Gravity. 

By  dividing  the  atomic  weight  of  an  element  by  its  specific  gravity 
we  obtain  the  atomic  volume,  i.e.,  the  volume  in  cubic  centimeters  oc- 
cupied by  a  quantity  of  the  substance  equal  to  its  atomic  weight  ex- 
pressed in  grams  (gram-atom).  For  example,  lithium,  atomic  weight 
7.01,  specific  gravity  0.59,  therefore  atomic  volume  is  11.9;  that  is  to  sav, 
7.01  grams  of  lithium  occupy  a  volume  of  11.9  cubic  centimeters  (0.59 
gram  Li:7.01  gram  Li::l  c.c.:a:).  For  the  different  modifications  of 
an  element  the  atomic  volume  is  different. 

In  regard  to  the  relation  of  the  atomic  volume  to  the  properties  of 
the  atoms  see  p.  56. 

The  molecular  volume  of  a  compound  is  the  volume  in  cubic  centi- 
meters occupied  by  a  quantity  of  the  compound  equal  to  its  molecular 
weight   taken   in  grams   (gram-molecule).     It  is  obtained  by   dividing 


PHYSICAL  PROPERTIES  OF  LIQUIDS.  37 

the  gram-molecule  of  the  compound  by  the  specific  gravity  of  the  com- 
pound. 

For  the  relation  of  the  molecular  volume  to  the  constitution  of  organic 
compounds  see  Part  III.  The  atomic  and  molecular  volumes  do  not 
correspond  to  the  actual  volumes  occupied  by  the  atoms  and  molecules, 
since  in  determining  the  specific  gravity  not  only  the  volumes  of  the 
atoms  and  molecules  are  measured,  but  also  the  space  between  them. 
Atomic  and  molecular  volumes  are  accordingly  the  volumes  which  con- 
tain equal  numbers  of  atoms  and  molecules. 

The  gram-volume,  or  specific  volume,  of  a  solid  substance  is  the 
volunie  occupied  by  1  gram  of  the  substance,  and  is  determined  by  divid- 
ing 1  by  the  specific  gravity  of  the  given  substance.  For  example,  the 
specific  gravity  of  lithium  is  0.59,  i.e.,  1  c.c.  of  lithium  weighs  0.59 
gram,  therefore  1  gram  of  lithium  will  occupy  a  volume  of  1.69  c.c.  (0.59 
gram  Li:l,0  gram  Li::l  c.c.:a:  c.c). 

e.  Optical  Properties. 
These  will  be  treated  under  liquids. 

•2.  Liquids. 

These  have  no  fixed  form,  but  assume  that  of  the  vessel  which  con- 
tains them.  Their  molecules  have  no  longer  a  definite  position  of  equi- 
librium, but  have  a  progressive  motion  in  addition  to  one  of  vibration 
and  rotation,  so  that  each  molecule  is  from  time  to  time  surrounded 
by  different  neighboring  molecules. 

a.  Boiling  and  Evaporation. 

On  being  cooled  to  a  definite  temperature  (freezing-point)  all  liquids 
become  solid;  on  being  heated  to  a  definite  temperature  (boiling-point) 
liquids  are  vaporized.  The  latter  is  true  only  for  such  liquids  as  vaporize 
without  decomposition,  but  in  the  case  of  all  liquids  there  is  a  definite 
formation  of  vapor  even  at  temperatures  below  the  boiling-point. 

If  the  formation  of  vapor  takes  place  only  at  the  surface  of  a  liquid, 
this  is  called  evaporation;  but  if  it  proceeds  also  within  the  liquid,  it  is 
called  boiling.  The  boiling-point  is  lower  the  lower  the  external  pres- 
sure, and  an  increase  in  the  external  pressure  causes  an  elevation  of  the 
b  iling-point. 

Every  liquid  boils  when  the  tension  of  its  vapor  equals  the  external 
pressure.  The  boiling-point  is  always  taken  as  that  temperature  at 
which  the  tension  of  the  vapor  is  equal  to  an  external  pressure  of  760  mm. 
of  mercury.  Many  substances  which  decompose  when  boiled  under 
atmospheric  pressure  can  be  boiled  under  diminished  pressure  without 
undergoing  any  decomposition.  The  boiling-point  is  constant  for  every 
pure  substance  and  is  therefore  a  valuable  means  for  the  identification, 
as  well  as  for  the  determination  of  the  purity,  of  a  substance. 

Under  certain  suitable  conditions  the  external  pressure  can  be  made 
much  lower  than  the  vapor  tension  of  the  liquid  without  causing  the  latter 
to  boil  (superheated  hquids,  analogous  with  supercooled  substances, 
p.  35). 

When  a  pure  liquid  begins  to  boil  the  temperature  remams  constant 
as  long  as  the  boihng  continues.     The  heat  of  vaporization  is  the  number 


38  GENERAL  CHEMISTRY. 

of  heat-units  which  are  required  to  transform  1  gram  or  1  kilogram  of 
liquid  into  vapor  having  the  same  temp^ature,  or  is  the  number  of  heat-' 
units  set  free  when  1  gram  or  1  kilogram  of  vapor  is  converted  into  liquid 
having  the  same  temperature  (see  Water  Vapor). 

For  the  relation  of  the  boiling-point  to  the  constitution  of  organic 
compounds  see  Part  III. 

h.  Specific  Gravity. 

The  calculation  of  the  specific,  atomic,  and  molecular  volumes  from 
the  specific  gravity  is  carried  out  as  in  the  case  of  solids  (p.  36). 

For  the  relation  of  the  molecular  volume  to  the  constitution  of  organic 
compounds  see  Part  III. 

c.  Spectrum. 

The  property  which  many  colored  solutions  have  of  absorbing  a  part 
of  the  light  split  up  by  a  prism.  For  the  application  of  this  property  to 
the  determination  of  their  chemical  nature  see  p.  45. 

d.  Refraction  of  Light. 

Every  transparent  substance  possesses  a  definite  power  of  refracting 
light,  and  the  quotient  of  the  sine  of  the  angle  of  refraction  (r)  into  the 
sine  of  the  angle  of  incidence  (i),  called  the  coefficient  or  index  of  refrac- 
tion (n),  is  a  constant  for  every  given  substance.     ^^ =  n.    This  is 

^  "^    ®  Siner 

of  great  assistance  in   identifying  a  substance  and  for  determining  its 

purity.     It  is,  however,   dependent  on  the  density  (specific  gravity,  d) 

of  the  given  substance  (also  on  the  pressure  and  temperature),  as  well 

n^  —  1    1 
as  on  its  state  of  aggregation.     By  the  use  of  the  formula    ^        '-r=R  a. 

factor  R  is  obtained  which  for  liquids  and  gases  is  dependent  only  on 
their  chemical  constitution.  This  is  known  as  the  specific  refractive 
power  or  specific  refractive  constant. 

The  product  of  the  specific  refractive  power  of  an  element  with  its 
atomic  weight  is  called  its  atomic  refraction. 

The  product  of  the  specific  refractive  power  of  a  compound  with 
its  molecular  weight  is  called  its  molecular  refraction. 

From  the  specific  refractive  power  of  a  liquid  mixture  (i.e.,  a  solution), 
when  the  specific  refractive  power  and  the  constitution  of  one  of  the  sub- 
stances is  known,  that  of  the  other  can  be  calculated.  On  the  other 
hand,  in  a  liquid  mixture  of  several  substances  of  known  refractive 
power  the  proportions  by  weight  in  which  the  different  substances  are 
present  can  be  calculated  from  the  specific  refractive  constant  of  the 
mixture. 

For  the  relation  of  the  specific  refractive  power  to  the  constitution 
of  organic  compounds  see  Part  III. 

•   e.  Rotation  of  the  Plane  of  Polarization. 

Many  organic  and  inorganic  compounds  rotate  the  plane  of  polar- 
ized light  to  the  right  or  left  and  are  therefore  called  dextrorotatory 
and  laevorotatory  respectively,  or,  in  general,  optically  active  or  cir- 
cularly polarizing.  A  small  number  of  these  compounds  show  this 
behavior  only  in  the  crystalline  state,  and  the  rotation  ceases  when 


ROTATION  OF   THE  PLANE  OF  POLARIZATION,        39 

they  are  dissolved  or  pass  over  into  the  Hquid  condition.  Very  few 
organic  compounds  belong  to  this  class.     A  much  larger  number  of  com- 

{)ounds,  of  wliich  all  are  organic,  exhi  it  optical  activity  when  in  the 
iquid  condition,  some  indeed  not  only  when  existing  as  liquids,  but  also 
when  in  the  form  of  gases. 

In  the  case  of  those  substances  which  possess  this  property  only  in 
the  crystalline  state,  their  behavior  must  be  attributed  to  the  arrangement 
of  the  molecules  in  the  crystal.  With  those  which  show  this  behavior 
in  the  fused,  dissolved,  or  gaseous  condition  it  cannot  be  assumed  that 
the  effect  is  due  to  any  arrangement  of  the  molecules,  since  these  are  free 
to  move  about  in  all  directions,  but  it  must  be  assumed  that  it  is  caused 
by  some  particular  arrangement  of  the  atoms  in  the  molecules.  Now 
it  has  been  shown  that  all  those  organic  con\pounds  which  are  optically 
active  when  fused,  dissolved,  or  gaseous  contain  at  least  one  asymmetric 
carbon  atom,  namel}',  a  carbon  atom  which  is  attached  to  four  dissimilar 
atoms  or  groups  of  atoms;    for  example, 

H3C.      yOH  HOv      /COOH 

lactic  acid  >X  »  malic  acid  >^^ 

H/     \COOH  IV      \CH,COOH. 

The  optical  acti\'ity  remains  through  all  reactions  which  do  not  alter 
the  asymmetry,  but  if,  as  shown  in  the  above  formulas,  only  one  OH 
group  is  replaced  by  an  H  atom,  the  optical  activity  vanishes  with  the 
asymmetry. 

On  the  other  hand,  however,  the  presence  of  an  asymmetric  carbon 
atom  does  not  always  produce  optical  activity,  since  every  optically 
active  compound  is  also  known  in  an  optically  inactive  modification 
which  can  be  split  up  into  two  optically  active  modifications.  In  the 
case  of  compounds  containing  two  asymmetric  carbon  atoms  it  is  more- 
over possible  to  obtain  still  another  inactive  modification  which  cannot 
be  further  resolved  into  two  active  forms  (see  Stereoisomerism). 

The  inactive  resolvable  modification  can  be  either  a  mechanical 
mixture  of  equal  numbers  of  molecules  of  the  dextro-  and  la^vorotatory 
variety,  which  then,  with  the  exception  of  the  optical  activity,  retains 
all  of  the  characteristics  of  its  components,  or  it  is  a  true  compound  of 
the  dextro-  and  Isevorotatory  modifications  which  differs  from  the  two 
active  forms  in  its  melting-point,  boiling-point,  etc.,  and  is  called  a 
racemic  modification  (since  it  was  first  observed  in  the  case  of  the 
tartaric  acids).     See  further  under  Isomerism,  Part  III. 

Compoimds  with  asymmetric  carbon  atoms  can  be  obtained  only 
by  separating  them  from  natural  products  or  by  fermentation  processes, 
or  bv  preparing  them  from  other  optically  active  substances.  From 
inactive  compounds  by  synthetical  processes  inactive  modifications 
are  always  obtained,  and  these  must  first  be  split  up  in  order  to  become 
opticallv  active.  The  separation  is  carried  out  with  the  assistance  of 
certain  bacteria  which  attack  one  modification  but  leave  the  other, 
or  by  the  preparation  of  compounds  with  certain  optically  active  sub- 
stances like  strvchnine,  brucine.  momhine.  and  cinchonme,  when  on 
evaporation  the  compounds  of  one  modification  crystallize  out  first  (seo 
further  under  Aspartic  Acid,  Malic  Acid,  Lactic  Acid,  Tartaric  Acid, 
Asparagine,  Artificial  Sugars,  etc.). 


40  GENERAL  CHEMISTRY. 

On  the  other  hand  many  optically  active  compounds  can  be  con« 
verted  into  inactive  ones  if  thev  are  heated  alone  or  with  water,  or  when 
certain  substances  are  added  to  their  solutions.  Moreover,  many  dextro- 
rotatory substances  can  be  transformed  into  la^vorotatory,  and  vice 
versa,  by  heating  them  with  water,  pyridine,  or  quinohne  to  141-170°. 

The  magnitude  of  the  rotation  of  a  compound  (the  angle  of  rotation) 
has  a  constant  value  for  every  substance  and  is  therefore  of  valuable 
assistance  for  the  identification  of  a  substance  and  for  detennining  its 
purity.  It  depends,  however,  on  the  temperature,  on  the  thickness, 
of  the  layer  through  which  the  light  passes,  and  on  the  wave  length  of 
the  light  itself. 

The  specific  rotatory  power  (a)  is  the  rotation  of  the  plane  of  polar- 
ization produced  by  a  layer  of  liquid  1  decimeter  in  thickness  which 
contains  1  gram  of  the  substance  in  1  cubic  centimeter  at  a  temperature 
of  20°.  The  light  used  is  the  yellow  sodium  light  having  a  wave  length 
corresponding  to  the  D  line  of  the  solar  spectrum.  This  is  denoted 
thus:  (a)r).  If  the  length  of  the  tube  containing  the  solution  is  I,  if 
a  is  the  angle  of  rotation  measured  for  a  layer  1  decimeter  in  thickness, 

and  if  d  is  the  specific  gravity  of  the  liquid,  then  for  liquids  (a)D=  t— %, 
and  for  solutions  containing  p  grams  of  substance  in  100  grams  of  solu- 
tion («)d  =  -^ -^      By  the  use  of  the  latter  fornmla  it  is    possible  to 

calculate  how  much  of  an  optically  active  substance  is  contained  in 
100  grams  of  a  solution,  if  all  the  other  quantities  are  known,  since 

p=  ,    ,   .       -   (quantitative  analysis  by  polarization). 

3.  Gases. 

Matter  in  the  gaseous  state  is  capable  of  completely  filling  any  given 
space.  In  gases  the  molecules  do  not  exert  any  mutual  attraction  on 
one  another,  but  move  about  in  straight  hnes  until  they  encounter  one 
another  or  are  stopped  by  some  other  resistance,  whereupon  they  again 
proceed  in  a  straight  line  in  some  other  direction.  They  thus  distribute 
themselves  about  in  all  directions  unless  they  are  prevented  by  some  im- 
penetrable barrier.  When  such  an  obstacle  is  encountered,  the  walls 
of  the  containing  vessel,  for  example,  they  exert  a  pressure  upon  this 
which  increases  with  the  number  of  rebounding  molecules  as  well  as 
with  their  mass  and  velocity.  This  is  known  as  the  expansive  force  or 
tension  of  the  gas. 

The  theory  which  explains  the  behavior  of  gases  and  their  pressure 
on  the  walls  of  the  containing  vessel  on  the  assumption  of  a  movement 
of  the  molecules  is  called  the  kinetic  theory  of  gases  (Kirr/aiS,  motion). 
Gases  which  can  be  liquefied  by  cooling  to  the  ordinary  temperature  of 
the  air  are  called  vapors  (see  below).  The  name  vapor  is  often  applied 
in  common  usage  to  colorless  aeriform  bodies  which  are  visible  and  which 
contain  innumerable  little  drops  of  liquid  carried  along  in  the  process 
of  evaporation.  In  scientific  usage  this  meaning  of  the  word  is  excluded. 
The  collecting  of  erases  is  carried  out,  according  to  their  solubility,  over 
water,  salt  solution,  or  mercury  (p.  51),  and  with  specifically  heavy 
gases  by  the  direct  displacement  of  air.     Because  of  the  evaporation 


I 


PHYSICAL  PROPERTIES  OF  LIQUIDS.  41 

of  the  water,  gases  evolved  from  aqueous  solutions  or  collected  over 
water  are  always  moist;  in  order  to  dry  them  they  are  conducted  through 
tubes  filled  with  substances  which  absorb  water  vapor  (alkali  hydroxides, 
calcium  oxide,  calcium  chloride,  sulphuric  acid,  phosphorus  pentoxide, 
etc.)- 

a.  Liquej action. 

All  gases  can  be  liquefied  by  cooling,  although  the  necessary  tem- 
perature is  often  more  than  a  hundred  degrees  below  the  zero-point.  All 
gases  can  also  be  liquefied  by  increasing  the  pressure,  but  only  when 
at  the  same  time  they  are  cooled  to  a  certain  definite  temperature,  which 
for  every  gas  is  different.  That  temperature  above  which  a  gas,  even 
under  the  greatest  pressure,  can  no  longer  be  liquefied  is  called  its  critical 
temp'irature .  The  pressure  exerted  by  a  gas  at  its  critical  temperature 
is  called  its  critical  pressure.  In  order  to  lic|uefy  a  gas  the  process  must 
therefore  be  carried  out  at  a  temperature  somewhat  below  its  critical 
temperature.  At  the  critical  temperature  and  the  critical  pressure  the 
volume  (the  critical  volume)  of  a  gas  is  the  same  as  that  of  an  exactly 
equal  weight  of  the  liquefied  gas.  Through  the  critical  temperature 
it  is  possible  to  sharply  define  gas  and  vapor.  Vapor  is  a  gas  at  any 
temperature  below  its  critical  temperature,  i.e.,  vapors  can  be  liquefied 
by  increasing  their  pressure,  while  gases  can  be  liquefied  only  by  an  in- 
crease in  pressure  accompanied  by  a  simultaneous  decrease  in  tempera- 
ture. It  is,  however,  under  certain  conditions  possible  for  a  vapor  to 
remain  unaltered  at  pressures  under  which  it  would  ordinarily  liquefy 
(supercooled  vapors,  analogy  to  supercooled  liquids,  p.  35).  The 
critical  temperature  (T)  and  the  critical  pressure  (P)  of  a  number  of  gases 
are  given  below: 

T.           P.                                                T.  P. 

Hydrogen -  220°    1 5  atm.  Chlorine + 146°  94  atm. 

Oxygen -118  50     "  Carbon  monoxide  -140  35     " 

Nitrogen. -146  36     "  Carbon  dioxide.  .  .  +  31  77     " 

Air -140  30     "  'Ammonia +130  115     " 

Nitrous  oxide. +   39    175     "  Hydrogen  chloride  +   53  S6     " 

Nitric  oxide -  93  71     "  Hydrogen  sulphide  + 100  92     " 

Argon -121  51     "  Sulphur  dioxide  .  .  +155  79     " 

If,  bv  removing  the  pressure  to  which  it  is  exposed,  a  liquefied  gas  is 
allowed  to  rapirjly  evaporate,  the  gas  evolved  will  remove  from  its  sur- 
roundings a  quantity  of  heat  equal  to  that  given  out  by  it  on  liquefaction 
(heat  of  vaporization).  As  a  result  of  this  the  liquefied  gas  still  remain- 
ing is  so  strongly  cooled  that  it  generally  solidifies. 

The  liquefaction  of  the  difficultly  liquefiable  gases  is  carried  out  on 
a  large  scale  by  the  use  of  Linde's  regenerative  apparatus,  which  em- 
ploys the  strong  cooling  resulting  from  the  expansion  of  compressed  ga.ses. 

The  apparatus  consists  of  a  pump  which  draws  the  gas  from  tiie 
generating  apparatus  and  then  compresses  it  to  the  required  pressure. 
From  the  pump  the  compressed  and  therefore  heated  gas  passes  through 
an  iron  pipe  surrounded  by  cold  water.  The  continuation  of  this  pipe 
is  a  spiral  tube  several  hundred  meters  in  length  surrounded  by  a  larger 
iron  pipe.     The  compressed  gas  flows  through  the  inner  tube  to  a  vessel 


42  GENERAL  CHEMISTRY. 

at  the  em],  where  it  is  allowed  to  expand  suddenly,  and  then  cooled  by 
expansion  it  flows  back  again  through  the  outer  pipe  to  the  compressor. 
By  this  process  the  gas  entering  through  the  inner  tube  is  cooled,  the 
cycle  beginning  anew  at  the  pump,  until  finally  after  repeated  cooling 
and  expansion  in  the  apparatus  the  temperature  falls  to  the  critical 
temperature  and  liquefaction  commences. 

Many  gases  are  supplied  to  the  trade  strongly  compressed  or  liquefied 
in  wrought-iron  cylinders,  which  under  these  conditions  are  attacked 
very  little  or  not  at  all  by  the  gases  within  them. 

h.  Volume  Relations. 

The  volumes  of  all  gases  at  any  given  temperature  vary  inversely 
with  the  pressures  to  which  they  are  subjected,  and  with  unvarying 
pressure  undergo  an  expansion  of  ^| 3  =  0.003665  of  their  volume  at 
0°  for  every  increase  in  temperature  of  1°  and  a  corresponding  contrac- 
tion for  every  decrease  of  1°  in  temperature.  For  the  explanation  of 
this  behavior  by  Avogadro's  hypothesis  see  p.  16. 

Gases  follow  the  laws  of  pressure  and  warming  only  when  in  a  dilute 
condition;  strongly  compressed  or  cooled  gases  show  more  or  less  marked 
deviation  from  the  laws,  according  to  whether  by  pressure  or  cooling 
they  can  be  more  or  less  readily  converted  into  liquids;  that  is,  they 
show  these  deviations  when  near  to  their  transformation  into  the  liquid 
state. 

These  variations  lead  to  the  conclusion  that  as  the  molecules  come 
closer  together  their  own  volumes  become  of  greater  moment  and  the 
attraction  of  one  for  the  other  (cohesion)  can  be  no  longer  neglected. 
As  a  fesult  of  this  mutual  attraction  the  pressure  necessary  to  produce 
a  given  compression  is  lessened,  and  this  reduction  of  the  pressure  is 
found  to  be  directly  proportional  to  the  square  of  the  density,  and  in- 
versely proportional  to  the  square  of  the  volume  (Van  der  Waals'  theorv). 

In  the  ordinary  chemical  operations  gases  are  not  weighed  but,  since 
it  is  more  convenient,  their  volume  is  measured,  and  from  this  their  weight 
is  calculated.  Since  the  volume  Of  a  gas  is  dependent  on  the  atmos- 
pheric pressure  and  temperature  (p.  15,  1),  as  well  as  on  the  water 
vapor  which  it  carries  (see  Water),  every  measured  gas  volume  (V) 
must  be  reduced  to  the  normal  volume  (F„)  which  the  dried  gas  would 
occupy  at  0°  and  a  barometric  pressure  of  760  mm.  This  normal  gas 
volume  is  often  merely  a  mathematical  assumption,  since  manv  sub- 
stances can  no  longer  exist  as  gases  at  0°.     The  reduction  is  carried  out 

by  means  of  the  following  formula:  Vo=  yeon +  0  0036657)'  ^^'  which 
0.003665  is  the  coefhcient  of  expansion  of  gases  (p.  15,  1),  T  the  observed 
temperature,  and  B  the  observed  pressure  (height  of  barometer)  in  mill'- 
meters.  Since  the  removal  of  water  vapor  is  inconvenient,  the  gas  to  be 
measured  is  brought  in  contact  with  water  in  order  that  it  may  become 
completelv  saturated  with  water  vapor,  and  then  from  the  observed  pres- 
sure in  milUmeters  (B)  a  quantity  is  subtracted  equal  in  millimeters  to 
the  tension  of  aqueous  vapor  at  the  temperature  of  observation. 

The  most  important  quantities,  with  relation  to  the  volume  of  a 
gas,  can  be  calculated  from  the  knowledge  of  its  molecular  weight  and 
the  weight  of  a  liter  of  oxygen  (=1.429  grams). 


VOLUME  RELATIONS  OF  GASES.  43 

The  absolute  weight  of  a  Uter  of  any  gas  is  found  by  multiplying 

its  molecular  weight  by  0.04466,  since 

Mol.  wt.         .  Mol.  wt.  of       , .    Wt.  of  liter      .       Wt.  of  liter 

of  oxygen        *  the  given  gas    * '     of  oxygen       *      of  given  gas 

32  :  M  ::        1.429  :  x 

M  •  1  429 
x=' —  ,  therefore  a;=  0.04466.     For  example,  the  weight  of  a  liter 

of  ammonia  gas,  NH3,  ib  17.07X0.04466=0.76  gram;  a  liter  of  hydrogen 
gas,  Hg^  is  2.02X0.04466=0.09  gram;  a  liter  of  air  (calculated  molecular 
weight=  28.95,  p.  44)  is  28.95X0.04466=1.293  grams. 

The  calculated  weights  per  liter  generally  differ  somewhat  from  those 
determined  by  direct  weighing,  since  the  gases  do  not  exactly  follow 
the  laws  on  which  the  calculation  is  based. 

The  gram-volume  or  specific  volume  of  gases,  namely,  the  volume  in 
cubic  centimeters  occupied  by  1  gram  of  the  given  gas,  is  found  by  divid- 
ing 1000  by  the  weight  of  1  liter  of  the  gas.  For  example,  the  gram- 
volume  of  ammonia" NH3=  1316  c.c,  since  0.76  g.  NH3  :  1.0  g.  ::  1000 
c.c.:a:  (x=1316). 

In  order  to  obtain  the  molecular  volume  or  mol.-volume  of  a  gas,  i.e., 
the  volume  in  cubic  centimeters  occupied  by  one'  gram-molecule,  the 
molecular  weight  is  multiplied  by  the  gram-volume,  or  the  molecular 
wight  is  divided  by  the  weight  of  1  liter.  For  example,  the  mole- 
cular volume  of  ammonia  NH3=  22400  c.c,  since  1  g.  NHgi  17.07  g. 
NH,::1316  c.c.:a:,  or  0.76  g.  NH3:17.07  g.  NHgiilOOO  c.c.:a;  (a:=22400 
c.c). 

The  molecular  volume  of  all  gases  is  22400  cc  =  22.4  liters,  which 
is  a  necessary  consequence  of  Avogadro's  hypothesis. 

A  simple  calculation  of  the  quantities  which  are  related  to  the  gas 
volume  is  possible  by  the  use  of  the  constant  22.4  in  combination  with 
the  molecular  weight.  For  example,  the  weight  of  a  liter  of  ammonia 
is  given  by  the  proportion  22400  c.c.  :  1000  c.c  : :  17.07  g.  NH.^ :  x, 
the  gram-volume  of  ammonia  by  the  proportion  17.07  g.  NH3  :  1  g. 
NH3::22400:a:. 

c.  Specific  Gravity  (Density). 

The  specific  gravity  or  density  of  a  gas  is  a  number  which  expresses 
how  many  times  heavier  or  lighter  a  gas  is  than  an  equal  volume  of  a 
gas  taken  as  unity  at  the  same  pressure  and  temperature.  The  com- 
parison between  equal  volumes  of  different  gases  is  always  made  at 
760  mm.   pressure  and  0°  temperature   (p  42). 

As  unit  for  the  determination  of  the  specific  gravity  of  gases  the 
weight  of  an  equal  volume  of  air  was  first  employed,  but  since  air  is  a 
mixture  of  different  gases,  the  unit  next  chosen  was  hydrogen.  Since, 
however,  the  latter  gas  can  be  purified  only  with  difficulty,  and  since, 
moreover,  it  is  the  lightest  of  all  gases  and  therefore  difficult  to  weigh 
(p.  17),  oxygen  has  now  been  taken  as  the  unit  of  specific  gravity,  just 
as  it  is  used  as  the  basis  of  atomic  and  molecular  weights.  In  order  to 
express  the  intimate  relation  between  the  specific  gravity  and  the  molec- 
ular weight  of  gases,  the  unit  chosen  is  not  oxygen=l,  but  oxygen  =  32 
(  =  the  molecular  weight  of  oxygen).  This  offers  the  advantage  that 
the  specific  gravity  and  the  molecular  weight  are  then  identical,  since 
the  molecular  weight  is  likewise  based  on  the  assumption  of  oxygen=32 
as  unit  (p.  18). 


44  GENERAL  CHEMISTRY. 

The  specific  gravity  of  a  gas  with  respect  to  another  gas  taken  as 
unit  is  found  by  dividing  its  molecular  weight  by  that  of  the  unit  gas. 
For  example,  it  is  found  that  the  specific  gravity  of  ammonia  with  respect 

17  07 
to  hydrogen  as  unit  =  8.53,  since 

Mol.  wt.  of       .         Mol.  wt.  of    . .       Sp.  gr.  of      .  Sp.  gr.  of 

hydrogen         *  ammonia      '  *       hydrogen       '  ammonia 

2.02  :  17.07  ::  1  :        a- (a;  =8.53). 

It  is  often  important  to  know  the  specific  gravity  of  a  gas  with  respect 
to  air.  The  gas  density  of  air  corresponds  to  the  molecular  weight  28.95, 
since 

Wt.  of  inter       .      Wt.  of  inter    ..    Mol.  wt.  of       .       Mol.  wt.  of 
of  oxvgen         '  of  air         *  *       oxygen  *  air 

1.429  :  1.293         ::  32  :     x(a:=  23.95). 

The  specific  gravity  of  a  gas  with  respect  to  air=  1  is  therefore  foimd 
by  dividing  the  molecular  weight  of  the  given  gas  by  28.95;  for  example, 

m  the  case  of  ammonia  ^^    -  =  0.59. 

But  the  specific  gravity  of  a  gas  can  also  be  found  by  dividing  the 
weight  of  1  liter  of  the  gas  bv  the  weight  of  1  hter  of  the  gas  taken  as 

1  429  1  293 

unit;  therefore  oxygen  is -^^-TT^  =15.9  times  and  air    '     '  ■  =  14.4   times 

1  429 
heavier  than  hydrogen;  and  further,  oxygen  is    '^  '  =1.105  times  and 

ammonia       '       =0.59    times   heavier  than    air.     The    specific    gravity 

of  a  gas  with  respect  to  water  is  one  one-thousandth  of  the  weight  of 

1.429  .     0.76 

a  liter  of  the  gas,  namely,  for  oxygen     „  „  ,  and  for  ammonia    ^„^  ,  since 

Wt.  of  1  nter     .        Wt.  of  1  liter    . .    Sp.  gr.  of        .         Sp.  gr.  of 
of  water  "         of  ammonia     '  *       water  *         ammonia 

1000  :  0.76  ::  1  :  x. 

d.  Spectra  and  Spectrum  Analysis, 
a.  Emission  Spectra. 

Glowing  solids  and  liquids  (e.g.,  calcium  light,  Welsbach  light,  the 
light  of  ordinary  illuminants  which  contain  glowing  carbon,  incandes- 
cent platinum,  etc.)  send  out  rays  of  light  of  all  refraetivities,  and  there- 
fore when  their  light  is  dispersed  and  split  up  by  a  prism  a  continuous 
spectrum,  which  is  not  dependent  on  the  nature  of  the  material,  is  ob- 
tained. 

Incandescent  gases  and  vapors  emit  but  few  light  rays  and  these 
of  definite  refractivity,  and  give  therefore,  when  their  fight  is  split  up 
by  a  prism,  a  partial  spectrum  (emission  spectrum),  consisting  of  bright, 
vertical  lines  or  bands,  which  depends  on  the  chemical  nature  of  the 
given  substance  and  therefore  serves  for  its  identification  (spectrum 
analysis).     Each  of  these  lines  or  bands  corresponds  to  rays  of  light  of 


SPECTRUM  ANALYSIS.  45 

definite  wave  length,  and  is  therefore  differently  refracted  from  the 
other  rays  of  light.  For  this  reason  the  lines  in  the  spectrum  appear 
in  the  same  place  and  no  one  line  can  cover  another,  so  that  any  one 
vaporized  substance  can  be  identified  in  the  presence  of  any  number 
of  others.  ^ 

Every  element  has  a  characteristic  spectrum,  and  likewise  every 
compound  if  it  is  stable  at  the  temperature  at  which  the  incandescent 
gas  is  formed.  Unstable  compounds  give  the  spectra  of  their  decom- 
position products.  Compounds  usually  show  a  banded  spectrum,  free 
elements  one  consisting  of  lines. 

The  apparatus  which  serves  for  obser/ing  the  spectrum  and  for  measur- 
ing the  position  of  the  lines  and  bands  is  called  a  spectroscope,  and  by 
its  use  quantities  of  substances  can  be  detected  which  are  far  too  small 
to  be  weighed  on  a  balance. 

The  observation  of  new  lines,  not  previously  noticed,  can  lead  to 
the  detection  of  new  elements,  as  was  the  case  with  caesium,  rubidium, 
thallium,   indium,   gallium,   germanium,   etc. 

In  order  to  convert  substances  into  the  gaseous  state  for  the  purposes 
of  spectrum  analysis,  they  are  brought  into  a  hot,  non-luminous  flame. 
In  the  case  of  compounds  of  the  metals,  the  spectrum  obtained  is  usually 
tnat  of  the  free  metal,  since  the  compounds  are  decomposed  by  the  flame. 
When  the  temperature  of  the  flame  is  insufficient  to  vaporize  the  sub- 
stance, then  in  the  case  of  metals  electric  sparks  are  passed  between 
thin  rods  composed  of  the  metal.  With  compounds  of  the  metals  the 
electric  sparks  are  passed  between  a  platinum  point  and  the  compound. 
Gases  are  brought  to  incandescence  by  enclosing  them  in  a  highly  rare- 
fied state  in  glass  tubes  through  which  the  current  from  an  induction 
coil  is  conducted.  The  fight  emitted  by  a  flame  colored  with  sodium 
or  one  of  its  compounds  gives  a  spectrum  consisting  of  a  single  yellow 
line,  potassium  and  its  compounds  give  a  spectrum  consisting  of  a  red 
and  a  violet  line,  etc. 

/?.  Absorption  Spectra. 

If  light  giving  a  continuous  spectrum  is  passed  through  colored  trans- 

f)arent  solids  or  liquids  (for  example,  colored  glass  plates  or  colored 
iquids)  and  if  a  spectrum  is  formed  from  this  light  with  the  help  of  a 
prism,  then  only  that  part  of  the  spectrum  appears  which  has  the  same 
color  as  the  substance  penetrated,  while  all  other  parts  of  the  spectrum 
are  absorbed  by  the  passage  of  the  light  through  the  colored  substance. 
Many  colored  solids,  liquids,  and  gases,  when  white  fight  is  passed 
through  them,  do  not  absorb  definite  colors,  but  only  a  part  of  them,  and 
therefore  give  a  discontinuous  spectrum  (absorption  spectrum)  con- 
taining dark  lines  or  bands.  The  position  of  the  absorption  bands  thus 
obtained  is  an  invariable  characteristic  of  each  of  the  given  substances 
and  therefore  serves  to  identify  a  given  substance  and  distinguish  it 
from  others. 

Reversal  of  the  Spectrum.  If  the  spectrum  of  white  light  which 
has  been  passed  through  a  flame  containing  sodium  vapor  is  examined, 
a  dark  line  will  be  noticed  in  a  position  exactly  corresponding  to  that 
of  the  vellow  sodium  line;  if  the  white  fight  has  passed  through  potassium 
vapor,  then  two  dark  fines  appear  in  the  positions  of  the  red  and  violet 
potassium  lines;  and  in  a  similar  manner  the  reversed  spectra  of  all  the 


46  GENERAL  CHEMISTRY. 

elements  can  he  obtained.  The  cause  of  this  reversal  of  the  spectra 
is  given  by  Kirchhoff's  law:  A  gas  or  vaporized  substance  absorbs  all 
light  rays  having  the  same  periods  of  vibration  as  those  which  the  sub- 
stance itself  sends  out,  while  it  is  transparent  to  all  other  light  rays, 
so  that  under  the  given  conditions  the  absorption  spectrum  of  a  sub- 
stance corresponds  to  its  emission  spectrum.  The  dark  lines  which 
appear  in  the  spectra  of  the  self-luminous  heavenly  bodies  are  explained 
by  Kirchhoff's  law,  if  it  be  assumed  that  these  bodies  consist  of  an  in- 
candescent hquid  or  solid  nucleus  surrounded  by  glowing  gases  or  vapors. 
By  comparing  the  absorption  spectra  of  the  heavenly  bodies  with  the 
emission  spectra  of  the  elements  it  is  possible  to  determine  what  elements 
exist  in  the  atmospheres  of  the  different  heavenly  bodies.  If  the  direct 
light  sent  out  from  the  sun  is  cut  off,  as  is  the  case  in  a  total  eclipse,  then 
the  only  spectrum  obtained  is  that  of  the  glowing  gases  surrounding 
the  sun,  which  then  consists  of  bright  lines  corresponding  to  the  different 
elements  constituting  the  solar  atmosphere. 

e.  Refraction  and  Rotation  of  Light. 
This  is  described  under  liquids. 

4.  Physical  Mixtures. 

Physical  mixture  is  the  name  applied  to  a  physically  and  chemically 
homogeneous  complex  of  different  substances  which  cannot  be  separated 
into  its  components  by  purely  mechanical  means.  Physical  mixtures, 
in  contrast  to  chemical  compounds  as  well  as  mechanical  mixtures,  have 
an  uncertain  composition  and  are  produced  by  a  uniform  mixing  together 
of  the  molecules  of  the  different  substances  constituting  the  mixture. 
The  separation  of  their  constituents  is  therefore  more  or  less  difficult, 
in  contrast  to  the  mechanical  mixtures,  whose  constituents  can  readily 
be  separated. 

Physical  mixtures,  without  reference  to  their  actual  state  of  aggre- 
gation, are  considered  as  solutions,  and  are  accordingly  distinguished 
as  gaseous,  liquid,  and  solid  solutions.  They  occupy  an  intermediate 
position  between  mechanical  mixtures  and  chemical  compounds. 

a.  Diffusion  and  Osmosis. 

When  two  liquids,  solutions,  or  gases  are  brought  into  contact  a 
gradual,  spontaneous  mixing  takes  place  until  the  composition  of  both 
is  the  same.     This  phenomenon  is  known  as  diffusion. 

While  the  diffusion  of  liquids  is  determined  by  their  nature,  all  gases 
when  brought  into  contact  can  mix  in  every  proportion  without  relation 
to  the  specific  gravity  of  the  gases.  If,  for  example,  a  vessel  containing 
carbon  dioxide  is  covered  by  one  containing  hydrogen,  although  the 
carbon  dioxide  is  twenty-two  times  heavier  than  the  hydrogen  it  will 
work  upward  through  the  hydrogen  and  the  latter  will  work  downward 
through  it,  until  the  mixture  of  the  two  becomes  perfectly  uniform  and 
homogeneous.  The  rate  of  diffusion  of  a  gas  is  inversely  proportional 
to  the  square  root  of  its  density,  so  that,  for  example,  the  rate  of  diffusion 
of  oxygen,  which  is  sixteen  times  as  dense  as  hydrogen,  is  only  one-fourth 
of  that  of  hydrogen. 

If  a  heavier  liquid  is  covered  with  a  lighter  one  with  which  it  is  mis- 


DIFFUSION  AND  OSMOTIC  PRESSURE.  47 

cible,  or  if  a  solution  is  covered  with  the  solvent,  then  the  lighter  liquid 
will  pass  into  the  heavier  and  the  dissolved  substance  will  pass  into  the 
lighter  solvent,  until  the  liquid,  throughout  every  part,  has  the  same 
composition.  The  dissolved  substance  therefore '  acts  with  respect  to 
the  pure  solvent  exactly  as  a  gas  behaves  with  respect  to  empty  space 
or  to  another  gas,  namely,  both  strive  to  fill  the  space  offered  to  them 
(gases  the  surrounding  walls,   solutions  the  surrounding  liquid). 

Similarly,  if  two  miscible  solutions  are  placed  in  direct  contact  with 
one  another,  the  substance  in  one  solution  diffuses  into  the  solution  of 
the  other  substance  until  the  dissolved  substances  are  uniformly  dis- 
tributed through  all  parts  of  the  liquid.  The  rate  of  diffusion  of  dis- 
solved substances  is  dependent  on  the  nature  of  the  substance  and  the 
nature  of  the  solvent,  as  well  as  on  the  concentration  and  temperature 
of  the  latter. 

In  the  case  of  diffusible  liquids,  as  well  as  in  the  case  of  all  gases,  the 
diffusion  is  not  prevented  if  the  substances  are  separated  by  a  porous 
partition. 

The  diffusion  of  gases  is  indepeiJeat  of  the  nature  of  the  separating 
diaphragm;  the  diffusion  of  liquids  and  solutions  through  a  porous 
partition  is  called  osmosis  {aoa/Aoi,  pushing)  and  is  dependent  on  the 
nature  of  the  partition  and  of  the  liquid.  Those  substances  which  can 
undergo  osmesis  in  solution,  among  which  are  included  many  acids  and 
all  crystalli/.able  substances,  are  called  crystalloids  in  contrast  to  those 
substances  which  apparently  cannot  undergo  osmosis,  the  so-called 
colloids  or  gelatinoids.  The  substances  included  in  the  latter  class  all 
belong  to  the  amorphous  substances  (p.  34)  and  dissolve  in  water  only 
to  form  the  so-called  coUoidal  solutions  (p.  53);  for  example,  glue  (colla, 
gelatine),  gums,  albumins,  dextrins,  the  hydroxides  of  the  heavy 
metals,  as  well  as  the  aqueous  solutions  of  certain  heavy  metals  (p.  53). 
The  osmosis  of  the  colloids,  owing  to  their  high  molecular  weights,  takes 
place  so  slowly  that  it  does  not  come  into  practical  consideration. 

Osmosis  can  serve  for  the  separation  of  aqueous  solutions  of  the 
crystalloids  from  the  colloids;  this  process  is  called  dialysis  and  is  carried 
out  with  an  apparatus  known  as  a  dialyser. 

This  consists  of  a  vessel  open  at  top  and  bottom,  having  a  bottom 
formed  by  a  permeable  membrane  (an  animal  bladder  or  parchment- 
paper),  and  dippin,^  with  its  lower  part  in  a  large  vessel  filled  with  water. 
If  an  aqueous  solution  of  a  colloid  and  a  crystalloid  is  placed  in  the  vessel 
with  the  membrane,  the  crystalloid  diffuses  into  the  outer  water  and 
the  outer  water  diffuses  into  the  inner  vessel  until  the  water  within  and 
without  is  of  the  same  strength  with  respect  to  the  crystalloid.  If  the 
dialyser  is  now  brought  into  a  vessel  containing  fresh  water,  the  process 
begins  anew,  and  after  repeated  renewal  of  the  external  water  the  dialyser 
finally  contains  an  aqueous  solution  of  the  colloid  only. 

b.  Osmotic  Pressure. 

Just  as  the  molecules  of  a  gas  have  a  tendency  to  disperse  and  thereby 
exert  a  pressure  on  the  walls  of  the  containing  vessel,  so  the  molecules 
of  a  dissolved  substance  behave  with  respect  to  their  solvent. 

In  order  to  determine  the  pressure  of  dissolved  substa,nces  on  their 
solvents,  it  is  necessary  to  employ  a  dialyser  with  a  special  membrane 
which  is  permeable  to  the  solvent  but  not  to  the  dissolved  substance. 


48  GENERAL  CHEMISTRY, 

Such  a  membrane  is  called  a  semipermeable  membrane,  and  consists 
of  a  porous  earthenware  cylinder  containing  in  its  pores  precipitated 
copper  ferrocyanide.  Other  semipermeable  membranes  are  also  found 
in  the  vegetable  and  animal  world. 

If  a  solution  is  placed  in  a  dialyser  having  a  semipermeable  membrane, 
and  the  whole  is  placed  in  a  vessel  containing  the  pure  solvent,  then 
the  molecules  of  the  dissolved  substance,  in  their 
,^^^t.  futile  efforts  to  diffuse  into  the  solvent,  will  exert 
on  the  membrane  a  pressure  which  is  called  the 
osmotic  pressure.  If  the  semipermeable  membrane 
is  considered  as  a  piston  which  can  be  moved  in  a 
vessel,  then  the  piston  will  be  lifted  by  the  osmotic 
pressure  and  the  pure  solvent  will  penetrate  into 
the  solution  until  both  liquids  have  the  same 
composition.  If,  however,  the  piston  is  so  weighted 
that  it  cannot  be  moved,  then  this  counterbalancing  of  the  piston  is 
equivalent  to  the  osmotic  pressure  exerted  by  the  molecules  of  the  dis- 
solved substance. 

In  very  dilute  solutions  the  molecules  of  the  dissolved  substances 
are  so  widely  separated  from  one  another  that  only  those  properties 
which  depend  upon  the  number  of  the  molecules  are  exhibited.  There- 
fore dilute  solutions  completely  correspond  with  gases  in  their  general 
behavior.  The  osmotic  pressure  of  dilute  solutions  follows  the  same 
laws  as  the  pressure  of  gases. 

As  shown  on  p.  43,  1  gram-molecule  cf  every  gas  at  0°  and  1  atmos- 
phere pressure  occupies  a  volume  of  22.4  liters.  If  the  gas  is  now  com- 
pressed to  a  volume  of  1  liter,  it  would  exert  a  pressure  of  22.4  atmos- 
pheres, and  exactly  the  same  osmotic  pressure  is  produced  when  1  gram- 
molecule  of  any  substance  is  contained  in  1  liter  of  solution.  If  the  weight 
of  a  substance  and  its  osmotic  pressure  are  known,  then  the  quantity 
by  weight  which  dissolved  in  1  liter  would  give  an  osmotic  pressure  of 
22.4  atmospheres  can  be  readily  calculated.  On  account  of  various 
difficulties  the  osmotic  pressure  is  generally  determined  from  other 
properties  of  solutions  which  stand  in  close  relation  to  the  osmotic  pres- 
sure, namely,  from  the  vapor  pressure,  boiling-point,  and  freezing-point 
of  solutions.  This  is  of  great  importance,  not  only  for  the  simplification 
of  molecular  weight  determinations,  but  also  in  medical  chemistry  for 
determining  the  osmotic  pressure  of  the  different  animal  fluids,  which 
cannot  be  carried  out  directlv.  If  a  solution  evaporates,  only  the  sol- 
vent is  given  off,  and  if  a  solution  freezes,  then,  at' firsts  only  1:he  solvent 
separates,  while  as  a  result  the  dissolved  substance  in  the  liquid  remain- 
ing is  compressed  into  a  smaller  volume.  Just  as  the  compression  of 
gases  increases  their  pressure,  so  the  concentrating  of  the  solution  in- 
creases here  the  osmotic  pressure,  whereby  the  vaporization  and  freez- 
ing of  the  solvent  becomes  more  difficult,  and  the  vapor  pressure  and 
freezing-point  are  correspondingly  lowered. 

Since  the  boiling-point  is  the  temperature  at  which  the  vapor  pressure 
of  a  liquid  is  in  equilibrium  with  the  .atmospheric  pressure,  therefore 
when  the  vapor  pressure  of  a  liquid  is  lowered  by  dissolving  some  sub- 
stance in  it,  it  requires  the  addition  of  a  greater  quantity  of  heat,  namely, 
a  higher  temperature,  in  order  that  its  vapor  pressure  may  again  equal 
the  atmospheric  pressure. 


GASEOUS  AND  SOLID  SOLUTIONS.  49 

From  this  follows  the  correspondence  between  ,  equimolecular  solu- 
tions with  respect  to  osmotic  pressure,  vapor  pressure,  boiling-point, 
and  freezing-point  as  mentioned  on  p.   19. 

Just  as  certain  gases  show  exceptions  to  the  gas  laws  (see  Dissocia- 
tion), so  there  are  a  series  of  compounds,  the  so-called  electrolytes,  which 
give  a  higiier  osaiotic  pressure  than  corresponds  to  their  molecular  weights 
(see  Electrolytic  Dissociation). 

c.  Gaseous  Solutions. 

In  contrast  to  other  substances,  gases  can  mix  with  one  another,  i.e., 
dissolve  in  one  another,  in  all  proportions.  In  gas  mixtures  every  gas 
behaves  with  respect  to  its  own  particular  properties  just  as  if  it  alone 
were  present  and  retains  its  individual  characteristics,  namely,  its  ex- 
pansive force,  refraction  of  light,  solubility  in  liquids,  specific  heat,  etc. 
For  example,  the  pressure  exerted  by  a  quantity  of  gas  occupying  a  given 
volume  is  equal  to  the  sum  of  the  separate  pressures  which  tlie  different 
gases  would  exert  if  they  alone  occupied  the  given  volume  (Dalton's 
law*).  Ihe  volume  of  a  gas  mixture  is  equal  to  the  sum  of  the  volumes 
of  its  constituents. 

Liquids  and  solids  dissolve  in  gases  only  when  they  can  evaporate, 
in  which  case  the  evaporation,  following  Dalton's  law,  takes  place  just 
as  if  an  air-free  space  were  present. 

d.  Solid  Solutions. 

Solutions  of  solid  substances  in  other  solid  substances  are  represented 
by  the  alloy,  which  are  homogeneous  (mostly  solid)  mixtures  of  metals 
in  indefinite  proportions  by  weight.  They  are  formed  by  melting  the 
metals  together  or  by  mixing  the  fused  metals.  In  the  case  of  most 
of  the  metals,  the  mixing  can  take  place  only  within  certain  limited 
proportions  by  weigh+. 

Under  solid  solutions  are  also  included  the  isomorphic  mixtures 
(mixed  crystals),  namely,  the  individual  crystals  which  separate  out 
from  mixtures  of  solutions  of  isomorpliic  salts  and  to  whose  formation 
the  given  salts  can  contribute  in  indefinitely  varying  proportions  (p.  23). 

Examples  of  solutions  of  liquids  in  solids  are  furnished  by  the  zeolites, 
certain  hydrated  silicate  minerals  from  winch  the  water  can  be  removed 
in  indefinite  quantities  or  be  replaced  by  other  liquids  without  producing 
an  alteration  in  their  external  appearance. 

Solutions  of  gases  in  solids  can  be  formed  by  many  porous  substances, 
such  as  charcoal,  or  certain  finely  pulverized  metals,  as  platinum,  palla- 
dium, and  gold,  since  these  substances  can  condense  gases  in  their  pores. 
Because  of  its  resemblance  to  absorption  (the  condensation  of  gases  in 
liquids)  this  phenomenon  is  known  as  absorption.  The  absorption 
phenomena  also  include  the  general  property  of  all  solid  substances  to 
condense  gases  on  their  surface,  as  well  as  the  property  of  many  porous 
substances  (i.e.,  substances  with  large  surfaces),  for  example  charcoal, 
to  remove  dissolved  substances  from  their  solutions. 

When  solid  mixtures  are  melted  either  the  whole  mixture  or  only 
one  constituent  becomes  hquid.  The  melting-point  (solidification- 
point)  is  lower  than  tliat  of  the  most  difficultly  fusible,  often  indeed 
lower  than  that  of  the  most  readily  fusible,  constituent,  since  the  melting- 

*  Also  called  Henry's  law. 


50  GENERAL  CHEMISTRY. 

point  of  a  substance  is  lowered  (p.  48)  when  another  substance  is  dis- 
solved in  it.  The  lowering  of  the  freezing-point  is  a  distinctive  feature 
of  the  alloys. 

If  a  solid  mixture  is  repeatedly  melted  and  then  allowed  to  solidify, 
it  often  happens  that  one  of  the  constituents  partially  separates,  but 
finally,  after  the  removal  of  the  separated  material,  a  mixture  of  con- 
stant composition  is  obtained.  This  mixture  always  has  a  lower  melting- 
point  than  the  original  mixture,  and  on  further  fusion  and  solidificaticn 
this  melting-point  remains  constant  and  the  mixture  does  not  further  alter 
in  composition.  Such  a  mixture  is  called  a  eutectic  mixture  or  cryo- 
hydrate^  and  the  temperature  at  which  it  commences  to  separate  is  called 
a  eutectic  point. 

e.  lAquid  Solutions. 

These  are  the  solutions  in  a  restricted  sense,  and  are  formed  when 
liquids  combine  with  either  gases  or  other  liquids  or  solids  to  form  a 
new,  entirely  homogeneous  liquid  having  new  properties. 

The  solubility  is  different  and  usually  limited  for  different  soluble 
substances  in  the  same  solvent  and  for  the  same  soluble  substance  in 
different  solvents.  It  is  dependent  on  the  temperature  and,  especially 
in  the  case  of  gases,  on  the  pressure.  Indeed  the  same  chemical  com- 
pound can  have  a  different  solubility  according  to  its  water  of  crystal-- 
lization.  The  greater  number  of  inorganic  compounds  are  insoluble 
in  alcohol,  while  carbon  compounds  are  mostly  soluble  in  alcohol  and 
ether,  and  their  solubility  decreases  with  an  increasing  content  of  carbon. 

Solutions  closely  resemble  chemical  compounds;  chemical  compounds 
of  the  dissolved  substance  with  the  solvent  often  separate  frcm  them; 
for  example,  many  anhydrous  salts  separate  from  their  aqueous  solu- 
tions with  water  of  crystallization. 

A  more  or  less  complete  separation  of  the  constituents  of  liquid  solu- 
tions can  be  effected  by  distillation. 

When  a  liquid  is  converted  into  vapor  and  the  vapor  again  condensed 
by  cooling  the  process  is  called  distillation.  In  this  process  dissolved 
gases  are  given  off  entirely  or  partially  (p.  53)  and  solid  substances 
are  left  behind. 

Rectification  is  the  repeated  distillation  of  a  liquid  for  the  purpose 
of  completely  freeing  it  from  admixtures. 

Dry  distillation  is  the  decomposition  of  non -volatile  organic  com- 
pounds by  heat  out  of  contact  with  the  air,  as  a  result  of  which  solid, 
liquid,  and  gaseous  decomposition  products  are  obtained. 

Fractional  distillation,  see  p.  53. 

A  solution  which  contains  so  much  of  the  dissolved  substance  that, 
under  the  given  conditions,  the  solvent  can  take  up  no  further  quantity 
is  called  a  saturated  solution. 

a.  Solutions  of  Gases  in  Liquids. 

The  solution  of  gases  in  liquids  is  also  called  absorption,  and  since 
the  gas  is  liquefied  (p.  41)  the  process  of  absorption  is  always  accom- 
panied by  the  evolution  of  heat.  The  most  difficultly  liquefiable  gases 
are  therefore  the  least  soluble.  Every  gas  dissolves  in  a  liquid  already 
saturated  witli  another  gas  exactly  as  if  the  other  gas  were  not  present. 
The  quantities  of  dissolved  gases  are  measured  according  to  their  volumes 


SOLUTIONS  OF  SOLIDS  IN  LIQUIDS.  51 

at  0^  an.l  1  atmosphere  pressure.  The  power  of  Hquids  to  dissolve  gases 
always  decreases  with  an  increase  in  temperature,  but  also  on  the  solidi- 
fication of  the  solvent  the  dissolved  gases  are  set  free.  Liquids  which 
already  contain  dissolved  litmids  or  solids  are  able  to  dissolve  gases 
less  than  pure  liquids  (collecting  of  gases  soluble  in  water  over  hot  water 
or  salt  solution). 

The  quantities  by  weight  of  gases  which  dissolve  are  directly  propor- 
tional to  the  pressures  of  the  gases  during  the  solution  process  (Law  of 
Henry-Dalton,  not  holding  in  the  case  of  very  readily  soluble  gases, 
since  here  chemical  combination  usually  occurs),  so  that  1  volume  of  a 
liquid  dissolves  at  2  atmospheres  pressure  double  the  quantity  by  weight 
(but  the  same  volume,  see  Boyle's  law,  p.  15)  of  gas  that  would  be  dis- 
solved at  1  atmosphere  pressure.  If  the  pressure  is  reduced,  then  a 
corresponding  quantity  of  the  gas  is  set  free  (foaming  of  champagne, 
soda-water,  etc.).  A  solution  of  ammonia  gas  in  water  will  give  off 
the  former  until  its  pressure  in  the  space  above  the  liquid  has  become 
sufficiently  great.  If  sulphuric  acid  is  now  introduced  into  this  space, 
it  will  combine  with  all  the  ammonia  gas  present,  so  that  fresh  quantities 
of  ammonia  will  be  evolved  by  the  solution  until  all  the  ammonia  which 
it  contains  will  have  been  removed. 

Notwithstanding  the  fact  that  the  total  pressure  which  is  exerted 
by  a  mixture  of  gases  is  equal  to  the  sum  of  its  partial  pressures — namely, 
the  pressures  which  each  of  the  gases  alone  exert — from  a  gaseous  mix- 
ture only  so  much  of  each  gas  will  be  absorbed  as  corresponds  to  its 
partial  pressure.  If,  therefore,  another  gas  is  conducted  through  or  over 
a  solution  of  a  gas,  all  of  the  dissolved  gas  which  has  separated  will  be 
removed,  as  a  result  of  which  its  partial  pressure  will  be  constantly  re- 
duced and  the  gas  at  first  dissolved  in  the  liquid  will  finally  be  entirely 
removed  from  it.  If  the  solution  of  a  gas  is  boiled,  the  vapor  of  the  sol- 
vent sweeps  off  the  quantities  of  the  dissolved  gas  which  have  separated 
until  the  liquid  no  longer  contains  any  of  the  gas  dissolved  in  it. 

fi.    Solutions  of  Solids  in  Liquids. 

Such  solutions  are  usually  formed  with  the  absorption  of  heat,  since 
the  molecules  of  the  dissolved  substance  are  driven  into  the  solvent 
with  a  certain  pressure,  the  solution  pressure,  and  accordingly  energy 
in  the  form  of  heat  is  withdrawn  from  the  surroundings.  The  case  is 
analogous  to  the  evaporation  of  a  liquid  or  a  solid  where  the  molecules  enter 
into  the  space  offered  to  them  with  a  certain  pressure,  the  vapor  pressure. 
Just  as  a  liquid  evaporates  until  the  pressure  of  the  vapor  formed  is 
equal  to  the  vapor  tension  of  the  liquid,  so  a  solid  substance  passes  into 
solution  in  a  liquid  until  the  osmotic  pressure  of  the  solution  comes  into 
equilibrium  with  the  solution  pressure  of  the  solid  substance.  If,  how- 
ever, a  salt  combines  with  a  part  of  the  solvent  to  form  a  chemical  com- 
pound, then  heat  will  be  evolved,  since  the  quantity  of  heat  which  is 
set  free  by  the  combination  is  greater  than  that  required  for  liquefaction. 
For  example,  anhydrous  calcium  chloride  dissolves  in  water  with  the 
evolution  of  heat,  since  it  combines  chemically  with  a  part  of  the  water. 
On  the  other  hand  calcium  chloride  containing  water  of  crystallization 
dissolves  in  water  with  cooling. 

The  absorption  of  heat  is  stronger  the  more  rapidly  the  solution 
takes  place;  and  further  in  the  case  of  aqueous  solutions  when,  instead 


52  GENERAL  CHEMISTRY. 

of  being  dissolved  in  water,  tlie  substance  is  mixed  with  ice  or  snow, 
since  these  are  tlion  liquefied  by  the  effort  made  by  the  soluble  substance 
to  pass  into  solution,  and  their  heat  of  fusion  (p.  33)  produces  a  further 
cooling.  Tlie  action  of  freezing  mixtures  depends  on  this  principle; 
for  example,  in  preparing  a  saturated  aqueous  solution  of  ammonium 
chloride  the  temperature  sinks  about  V6°,  of  calcium  chloride  about 
23°,  of  ammonium  sulpliocyanide  about  31°;  on  mixing  1  part  of  common 
salt  with  2  parts  of  snow  the  temperature  sinks  to  —20°,  on  mixing  2 
parts  of  calcium  chloride  and  1  part  of  snow  to  —42°. 

If  heat  is  absorbed  on  dissolving  a  solid,  then  generally  the  addition 
of  heat  increases  the  solubility  of  the  substance.  In  the  case  of  many 
substances,  however,  the  increase  in  the  solubility  is  only  very  slight 
(e.g.,  in  the  case  of  common  salt),  in  the  case  of  many  the  solubility 
actually  decreases  (e.g.,  gypsum,  calciuai  hydroxide),  and  in  some  cases 
tlie  solubility  increases  up  to  a  certain  temperature  and  then  decreases 
(Glauber's  salt). 

Hot  saturated  solutions  of  salts,  when  they  are  allowed  to  cool  with- 
out being  disturbed  and  are  protected  from  dust,  do  not  separate  out 
any  of  the  dissolved  substance,  although  after  coohng  they  contain  much 
more  of  the  dissolved  substance  than  is  possible  under  ordinary  con- 
ditions. Such  solutions  are  called  supersaturated  solutions  (analogy  to 
superfused  solids,  p.  35). 

If  into  such  a  solution  there  is  introduced  even  an  infinitely  small 
quantity  of  the  salt  which  is  contained  in  the  solution  or  of  some  other 
salt  which  is  isomorphic  with  this,  then  the  excess  of  the  dissolved  salt 
separates  until  a  saturated  solution  is  formed  (see  Sodium  Sulphate). 
The  separation  of  the  excess  of  tlie  dissolved  salt  can  also  be  caused 
by  dust  falling  into  the  solution  or  by  stirring  the  solution  with  a  glass 
rod,  but  this  only  liappens  when  the  objects  introduced  into  the  solution 
are  contaminated  by  traces  of  the  salt  which  is  contained  in  the  solution. 

Saturated  solutions  are  in  stable  equilibrium,  supersaturated  solu- 
tions are  in  unstable  equilibrium.  Mother-liquor  is  the  name  given 
to  a  salt  solution  from  which  by  evaporation  or  cooling  a  part  of  the 
dissolved  salt  has  been  separated,  while  a  part  of  the  salt,  and  partic- 
ularly all  the  more  read'lv  soluble  salts,  still  remains  dissolved  in  it. 

The  freezing-point  of  liqui  Is  is  lowered  when  solid  substances  are 
dissolved  in  them,  and  the  l^oiling-point  is  raised.  The  laws  governing 
this,  which  can  serve  for  the  determination  of  the  molecular  weights 
and  their  relation  to  the  osmotic  pressure  of  dilute  solutions,  have  been 
already  mentioned  on  p.  48. 

These  laws  apply  only  approximately  in  tlie  case  of  concentrated 
solutions,  just  as  the  gas  laws  no  longer  accurately  apply  to  gases  when 
they  approach  their  points  of  liquefaction. 

y.  Solutions  of  Liquids  in  other  Liquids. 

These  solutions  usually  take  place  with  the  evolution  of  heat.  The 
limit  of  the  mutual  solubilities  of  two  liquids  in  the  case  of  many  liquids 
is  greater  with  increasing  temperature,^  in  the  case  of  many  others  is 
less.  Many  liquids  mix  in  all  proportions;  for  example,  alcohol  with 
water.  The  alteration  of  the  composition  of  mixed  liquids  by  distilla- 
tion (p.  .50)  always  proceeds  in  such  a  manner  that  the  vapor  pressure 
decreases,  namely,  the  boiling-point  rises. 


SOLUTIONS  OF  LIQUIDS  IN  LIQUIDS.  53 

Two  liquids  insoluble  in  one  another  arrange  themselves,  according 
to  their  specific  gravities,  one  above  the  other;  for  example,  water  and 
benzene.  If  a  mixture  of  volatile  substances  of  this  character  is  distilled, 
the  mixture  which  passes  over  has  a  constant  composition  so  long  as 
both  constituents  are  present  in  the  distilling  vessel.  The  boiling-point 
of  the  mixture  is  lower  than  that  of  either  of  the  constituents. 

Two  liquids,  of  which  each  is  only  slightly  soluble  in  the  other,  like- 
wise give  a  mixture  containing  two  layers  each  of  which  consists  chiefly 
of  one  of  the  liquids.  On  distillation  the  same  relations  pertain  as  in 
the  case  of  non-miscible  liquids;  the  boiling-point  of  the  mixture  can 
be  lower  than  the  boiling-point  of  the  most  readily  volatile  liquid;  it 
can  also  be  higher,  but  not  higher  than  the  boiling-point  of  the  most 
difficultly  volatile  constituent. 

Two  liquids  which  are  miscible  in  all  proportions  show  on  distillation 
the  following  complex  relations: 

The  boiUng-point  of  the  mixture  can  be  lower  than  that  of  the  more 
readily  volatile  constituent;  on  distillation  a  mixture  having  a  constant 
composition  and  a  low  and  constant  boiling-point  passes  over,  so  that 
the  residue  finally  consists  of  that  constituent  which  was  present  in 
excess. 

The  boiling-point  of  the  mixture  can  also  be  higher  than  that  of 
either  of  the  constituents;  on  distillation  at  first  that  constituent  which 
is  present  in  excess  passes  over  until  the  remainder  has  reached  such 
a  composition  that  its  boiling-j)oint  rises,  after  which  a  constant  mixture 
of  constant  higher  boiling-point  distils  over.  Such  constant  boiling 
mixtures  occur  in  the  case  of  the  aqueous  solutions  of  volatile  acids  (see 
hydrochloric,  sulphuric,  and  nitric  acids).  If,  for  example,  a  solution 
of  nitric  acid  be  heated,  then  in  the  case  of  a  dilute  solution  water  passes 
over,  in  the  case  of  a  concentrated  solution  nitric  acid  passes  over,  until 
a  temperature  of  121°  is  reached,  after  which  a  constant  mixture  of 
68  parts  nitric  acid  and  32  parts  water  distils  over.  Such  mixtures 
were  formerly  considered  to  be  chemical  compounds,  but  their  content 
of  water  does  not  correspond  to  the  law  of  multiple  proportions  and 
their  composition  alters  with  the  pressure. 

The  boiling-point  of  the  mixtures  can  be  higher  than  that  of  the 
more  readily  volatile,  but  lower  than  that  of  the  more  difficultly  volatile, 
constituent,  so  that  the  boiling-points  of  all  possible  mixtures  therefore 
lie  betwp-en  those  of  the  pure  constituents.  Therefore  in  the  process 
of  distillation,  since  the  boiling-point  always  rises,  that  portion  passing 
over  first  will  contain  more  of  the  lower  boiling  constituent,  that  part 
going  over  last  will  contain  more  of  the  higher  boiling  constituent,  so 
that  by  submitting  the  first  portion  to  repeated  distillation  the  separate 
constituents  can  be  separated  more  and  more  from  one  another  (frac- 
tional distillation). 

d.  Colloidal  Solutions. 

Of  the  colloids,  i.e.,  substances  apparently  incapable  of  undergoing 
osmosis,  only  a  few  are  directly  soluble  in  water.  On  the  other  hand, 
however,  it  is  possible  to  dissolve  the  remainder  of  them  in  water  in  the 
presence  of  salts,  acids,  etc.,  and  by  dialysis  to  convert  these  solutions 
mto  pure  aqueous  solutions,  the  so-called  colloidal  solutions.  Gold, 
silver,  mercury,  and  various  other  metals  can  form  colloidal  solutions 
when  an  electric  arc  is  formed  under  water  between  electrodes  of  the 


54 


GENERAL  CHEMISTRY. 


given  metal,  which  causes  the  metal  to  be  finely  pulverized  and  dis- 
solved. All  colloidal  solutions  have  on  the  one  hand  the  properties 
of  true  solutions,  on  the  other  hand  the  properties  of  substances  very 
finely  divided  in  water.  Many  colloidal  solutions  can  gelatinize  or  co- 
agulate on  the  addition  of  foreign  substances,  namely,  of  salts,  and  with 
many  this  process  can  take  place  spontaneously.  Others,  for  example 
gelatine,  agar-agar,  etc.,  solidify  only  below  certain  definite  temperatures 
and  above  this  temperature  become  again  liquid.  The  gelatinized  col- 
loidal solutions  are  called  geles  or  hydrogeles;  they  swell  up  strongly 
in  water  by  absorbing  it,  and  many  dissolve  on  the  addition  of  much 
water  (e.g.,  glue).  They  can  dissolve  crystalloids,  but  not  colloids, 
and  permit  their  diffusion  (use  of  gelatine  for  bacteria  culture,  photo- 
graphic dry  plates,  etc.).  The  liquid  colloidal  solutions  are  also  called 
soles;  certain  soles  of  the  heavy  metals,  for  example  platinum  and 
gold,  exhibit  the  properties  of  enzymes  and  are  therefore  also  called 
inorganic  enzymes.  Like  organic  enzymes,  the  action  of  these  can  be 
weakened  by  certain  poisons. 

RELATIONS    BETWEEN  ATOMIC  WEIGHT  AND   PROPERTIES  OF 
THE  ELEMENTS. 

If  the  elements  are  compared  with  one  another  with  respect  to 
their  properties  and  their  compounds,  it  is  evident  that  they  can 
be  divided  into  groups  or  families,  whose  members  show  great  simi- 
larity to  one  another.  Other  separate  members  of  these  groups 
show  relations  to  other  groups  and  thus  form  connecting  Hnks  between 
the  groups.  These  relations  of  the  elements  are  most  clearly  ex- 
pressed when  they  are  arranged  according  to  the  magnitude  of  their 
atomic  weights,  when  it  is  found  that  the  succeeding  elements 
exhibit  apparently  irregularly  increasing  properties,  but  that,  after 
the  passage  of  a  given  period,  the  chemical  and  physical  behavior  of 


Group  I. 

Group  II. 

Group  III. 

Group  IV. 

Hydrogen     { 

Compounds    f 

Highest  Oxy-    1 

genCompound  f 

Unknown 
Unknown 

MH 
M2O 

MH2 
MO 

MH3 
M2O3 

Period.     Series. 

I.              1. 

II.             2. 

III.         {    I 

IV.    ]i: 

1 10. 

Helium  4 
Neon  20 
Argon  40 

Krypton  82 

Xenon  128 

Lithium  7 
Sodium  23 
Potassium  39 

Copper  64 
Rubidium  85 

Silver  108 
Csesium  133 

Gold  197 

Beryllium  9' 
Magnesium  24 

Calcium  40 
Zinc  65 

Strontium88 
Cadmium  112 

Barium  137 

Mercury  200 

Boron  11 
Aluminium  27 

Scandium  44 
Gallium  70 

Yttrium  89 
Indium  114 

Lanthanum,  etc.,  138. 

Ytterbium  173 

Thallivmi  204 

PERIODIC  SYSTEM. 


65 


the  following  elements  suggests  or  indeed  repeats  that  of  the  elements 
which  precede  them.  The  properties  of  the  elements  are  periodic 
functions  of  their  atomic  weights  (Periodic  law).  If  the  elements  are 
so  arranged  according  to  the  magnitude  of  their  atomic  weights 
that  those  similar  elements  which  recur  after  certain  periods  stand 
one  below  the  other,  then  these  vertical  rows  form  the  groups  or 
families,  while  the  horizontal  rows  contain  the  periods,  that  is, 
the  elements  whose  atomic  weights  lie  between  the  successive  mem- 
bers of  one  family.  The  arrangement  of  the  elements  according  to 
this  system  is  called  the  periodic  or  natural  system  of  the  elements 
and  is  shown  in  the  table  below.  In  this  the  elements  fall  into 
five  periods  consisting  of  ten  rows,  and  in  eight  groups,  of  which 
the  second  to  the  eighth  each  forms  a  side  group  as  indicated  by  a 
horizontal  displacement  to  the  right  of  certain  of  the  elements  in- 
cluded in  the  vertical  rows.  In  this  way  those  elements  of  a  group 
which  show  the  greatest  similarity  to  one  another  are  brought  to- 
gether. The  periods  are  distinguished  as  large  and  small  periods 
according  to  the  number  of  elements  which  are  contained  in  them. 
The  elements  of  every  group  (vertical  row)  show  differences  between 
the  atomic  weights  which  closely  correspond  to  those  between  the 
atomic  weights  of  the  other  groups,  and  the  same  is  the  case  in  the 
periods  (horizontal  rows). 

The  periodic  system  makes  it  possible  to  divide  the  elements 
comprehensively,  to  check  the  accuracy  of  the  atomic  weight  deter- 
minations, and  to  predict  the  existence  and  properties  of  elements 
which  are  still  undiscovered. 


Group  V. 

Group  VI. 

Group  VII. 

Group  VIII. 

MH4 

MO2 

MH3 
M2O5 

MH2 
MO3 

MH 
M2O7 

Carbon  12 
Silicium  28 

Titanium  48 
Germanium  72 

Zirconium  91 
Tin  118 

Lead  207 

Thorium  232 

Nitrogen  14 
Phosphorus  31 

Vanadium  51 
Arsenic  75 

Niobium  94 
Antimony  120 

Tantalum  183 
Bismuth  208 

Oxygen  16 
Sulphur  32 

Chromium  52 
Selenium  79 

Molybdenum  96 
Tellurium  128 

Tungsten  184 

Uranium  239 

Fluorine  19 
Chlorine  35 

Manganese,  etc.,  55 
Bromine  80 

Ruthenium  ,etc .  ,102 
Iodine  127 

Osmium,  etb.,  191 

56  GENERAL  CHEMISTRY. 

The  four  elements  with    "etc."    affixed  each  represent  a  subgroup 
of  elements  in  the  system  having  almost  equal  atomic  weights  and  show- 
ing great  similarity  to  one  another.    For  example: 
Manganese,  etc.    =  Manganese     55,  Iron  56,  Cobalt         59,  Nickel       58.7. 
Ruthenium,  etc.  =  Ruthenium  102,  Rhodium  103,  Palladium  106. 

Osmium,  etc.        =Osmium        191,  Iridium     193,  Platinum   195. 

The  elements  standing  below  one  another  in  these  subgroups  form 
many  similarly  constituted  compounds. 

Lanthanum,  etc.  =  Lanthanum  138,  Cerium  140,  Praseodymium  141, 
Neodymium  144. 

Samarium  150,  Gadolinium  156,  Erbium  166,  and  Thulium  171  can- 
not be  satisfactorily  inserted  in  the  system. 

Among  the  physical  properties  of  the  elements  which  show  a  direct 
relation  to  the  atomic  weight  are  included  the  specific  gravity  and  atomic 
volume  (p.  36),  the  extensibility,  fusibility,  and  volatility,  the  specific 
refractive  power,  the  specific  heat,  the  conductivity  for  heat  and  elec- 
tricity, and  the  electrochemical  character.  All  of  these  properties  show 
a  maximum  or  minimum  in  the  middle  of  the  periods  (horizontal  rows). 
For  example: 

Third  Period.            K         Ca  V         Cr       Mn  Fe        Co        Ni 

Sp.gr 0.87     1.6  5.5      6.8       7.2  7.9       8.5      8.8 

Atomicvol 45.40  25.2  9.3       7.7       6.9  7.1       6.9       6.6 

Melting-point 62°    760°  3000°  3000°  1900°  1800°  1800°  1600° 

Third  Period.  Cu  Zn  Ga  Ge  As  Se  Br 

Sp.gr 8.8  7.1  5.9  5.5  5.6  4.5  2.9 

Atomicvol 7.2  9.0  11.6  13.1  13.2  17.5  26.9 

Melting-point 1100°  420°  30°  900°  500°  217°  -8° 

In  the  case  of  the  elements  of  many  groups  (vertical  rows)  the  specific 
gravity,  the  fusibility,  etc.,  increases  with  the  atomic  weight.  For  example: 

Second  Group.  Li  Na  K  Rb  Cs 

Sp.gr 0.59  0.97  0.87  1.5  1.8 

Melting-point 180°         96°  62°  38.5°  26° 

Boihng-point 900°  740°  670°  500°  270° 

Third  Group.                                   Be  Mg  Zn  Cd  Hg 

Sp.gr 1.8  1.7  7.1  8.6  13.5 

Melting-point 1000°  700°  420°  320°  -39° 

Boihng-point 1600°  1300°  950°  750°  357° 

In  the  successive  periods  (horizontal  rows)  the  elements  continually 
assume  a  more  metallic  character;  the  first  period  contains  2  metals, 
the  second  3,  the  third  and  fourth  periods  11,  the  fifth  only  metals. 

In  the  case  of  the  chemical  properties  the  dependence  of  these  on 
the  atomic  weight  is  shown  in  the  following. 

The  groups  (vertical  rows)  contain  the  elements  which  show  the 
greatest  chemical  similarity.  The  first  group  contains  the  chemically 
mdifferent  elements  of  unknown  valence,  He,  Ne,  A,  Kr,  X;  the  two 
following  groups  contain  the  elements  which  form  the  strong  bases  Li, 
Na,  K,  Rb,  Cs,  and  Be,  Mg,  Ca,  Sr,  Ba;  this  basic  character  falls  off  in 
the  middle  groups  and  gradually  passes  over  into  an  acid-forming  char- 
acter. 


PERIODIC  SYSTEM.  67 

The  valence  of  the  elements  increases  up  to  the  fourth  group  and 
then  decreases  proportionately. 

In  the  case  of  the  oxygen  compounds  a  steady  increase  in  valence 
is  shown;  the  increase  in  oxygen  corresponds  to  one-half  atom  from 
member  to  member.     For  example: 

I  II  III  IV  V  VI  VII 

Na^O  MgO         AlA  SiO^  PA  SO3  Cl^O, 

(NaO^)       (MgO,)    (AlO^^)       (SiO,)       (PO,^)       (SO3)       (€103^) 

In  the  case  of  the  hydroxides  the  number  of  the  hydroxide  groups  at 
first  increases  and  then  falls  off,  while  a  number  of  oxygen  atoms  and 
the  valence  steadily  increase.     For  example: 

Na(OH),.Mg(OH)2.Al(OH)3.Si(OH),.PO(OH)3.SO,(OH)2.C103(OH)j. 

The  periodic  system  assumes  the  existence  of  elements  as  yet  unknown, 
as  is  shown  by  the  gaps  in  the  table.  Since  the  properties  of  these  ele- 
ments are  influenced  by  their  position  in  the  system,  these  can  be  pre- 
dicted with  comparative  accuracy;  in  fact  such  gaps  have  already  been 
filled  by  the  discovery  of  germanium,  gallium,  and  scandium.  Their 
properties  have  been  found  to  completely  agree  with  those  which  were 
predicted  for  them. 

The  periodic  system  serves  to  check  the  atomic  weights.  Since 
the  properties  of  an  element  bear  a  close  relation  to  its  atomic  weight, 
so  the  properties  of  an  element,  as  well  as  its  atomic  weight,  can  be  made 
use  of  in  arranging  the  element  in  the  periodic  system.  If  now  an  ele- 
ment, according  to  its  determined  atomic  weight,  would  occupy  a  posi- 
tion in  the  system  into  which  it  would  not  fit  according  to  its  properties, 
then  it  can  generally  be  assumed  that  there  is  an  error  in  the  determina- 
tion, and  a  redetermination  of  the  atomic  weight  should  be  undertaken 
(p.  25). 

The  fact  that  the  properties  of  the  elements  are  functions  of  their 
atomic  weights  has  led  to  the  conjecture  that  the  elements  are  built 
up  from  one  or  more  fundamental  substances  and  are  therefore  at  present 
indivisible  (aro/ioi)  only  because  there  is  no  means  at  hand  for  split- 
ting them  up  into  smaller  particles. 

On  the  other  hand  it  is  asserted  that  the  properties  of  the  elements 
are  not  only  influenced  by  their  atomic  weight,  but  also  by  their  molecular 
weight  and  the  energy  relations  in  the  molecule.  Thus,  for  example, 
through  the  appearance  of  the  allotropic  modifications  of  the  elements 
(see  Ozone)  a  molecular  substance  of  quite  different  properties  can  be 
formed  by  the  combination  of  a  different  number  of  similar  atoms.  The 
present  form  of  the  periodic  system  cannot  be  final,  since  it  exhibits 
many  exceptions;  it  also  offers  no  explanation  of  the  fact  that  many 
elements  form  several  series  of  compounds  which  differ  from  one  another 
niuch  more  than  thev  differ  from  series  of  compounds  formed  by  entirely 
different  elements  occupying  positions  in  other  periods. 


II.   AFFINITY. 
CHEMICAL  AFFINITY. 

The  study  of  affinity  includes  the  study  of  chemical  mechanics 
and  the  transformation  of  chemical  energy  into  mechanical  energy 
(volume,  surface,  and  motion  energy),  or  into  non-mechanical  energy 
(heat,  electric,  and  radiant  energy). 

In  chemical  reactions  the  production  or  absorption  of  heat,  elec- 
tricity, or  light  takes  place,  and  these  different  sorts  of  energy  are 
produced  from  all  or  a  part  of  the  chemical  energy.  Conversely, 
heat,  electricity,  and  light  are  often  the  cause  of  chemical  reactions,  and 
during  their  progress  an  equivalent  transformation  of  the  given 
energy  into  chemical  energy  takes  place. 

Chemical  energy  is  the  most  complex  of  all  forms  of  energy  and 
the  least  understood,  and  the  only  method  by  which  it  can  be  more 
closely  investigated  is  by  transforming  it  into  other  forms  of  energy. 
It  is  simplest  to  transform  it  into  heat. 

The  knowledge  of  the  actual  nature  of  chemical  affinity  is  at  pres- 
ent as  unfathomable  as  that  of  gravity,  but  great  progress  has  been 
made  in  the  study  of  its  action,  as  well  as  its  dependence  on  mass, 
temperature,  and  pressure.  The  consideration  of  the  different  forms 
of  chemical  reactions  leads  to  the  conclusion  that  the  assumption  of  a 
force  of  affinity  considered  as  a  force  of  attraction  is  not  only  of 
little  advantage  in  explaining  chemical  reactions,  but  is  often  directly 
contrary  to  experience. 

For  example,  when  water  (HgO)  acts  on  glowing  iron  (Fe),  ferro- 
ferric  oxide  (Fe^OJ  and  hydrogen  (H)  are  formed,  from  which  it  must 
be  assumed  that  the  chemical  affinity  of  oxygen  is  greater  for  iron  than 
for  hydrogen:  3Fe  +  4HOH=re304  +  4H2. '  If,  however,  hydrogen  is 
allowed  to  act  on  glowing  ferro-ferric  oxide,  iron  and  water  are  produced, 
from  which  it  must  be  assumed  that  the  chemical  affinity  of  oxygen 
is  greater  for  hydrogen  than  for  iron. 

Since  these  assumptions  cannot  both  be  right,  the  theory  which  has 
led  to  these  assumptions,  namely,  the  theory  of  chemical  affinity,  must 
be  wrong. 

58 


CHEMICAL  MECHANICS.  59 

The  idea  of  atoms  having  attractive  forces  has  therefore  been 
more  and  more  abandoned,  and  it  has  become  usual  to  consider  the 
atoms,  as  well  as  the  molecules  built  up  from  them,  as  actively  moving 
masses,  whose  relations  to  one  another  are  determined  by  the  form 
and  magnitude  of  the  motion  (kinetic  nature  of  affinity). 

CHEMICAL  MECHANICS. 

Chemical  mechanics  treats  of  the  rate  or  velocity  of  chemical 
reactions  (chemical  kinetics  or  dynamics)  and  the  equilibrium  rela- 
tions which  are  established  after  the  progress  of  chemical  reactions 
(chemical  statics). 

Mechanics  teaches  that  every  system  of  bodies  strives  to  approach 
a  state  in  which  the  amount  of  energy  which  can  be  transformed 
into  work  (the  available  energy)  is  as  small  as  possible.  Chemical 
reactions  therefore  often  take  place  spontaneously  on  bringing  the 
given  elements  together;  for  example,  arsenic  and  chlorine  combine 
immediately  to  form  arsenic  trichloride. 

The  starting  of  a  chemical  reaction  often  requires  the  action 
of  some  external  influence,  such  as  heat,  electricity,  or  light.  This 
involves  a  loosening  of  the  chemical  energy,  since  a  part  of  the  mole- 
cules must  first  be  split  up  into  atoms,  or  the  union  of  the  atoms 
in  the  molecule  must  first  be  severed  before  the  chemical  reaction 
becomes  possible.  If  this  has  been  started  in  this  manner,  then  it 
proceeds  of  itself.  In  those  chemical  reactions  which  proceed  with 
the  absorption  of  heat,  on  the  other  hand,  energy  must  be  con- 
tinually supplied,  since  otherwise  the  reaction  stops. 

The  phenomena  of  chemical  kinetics  and  also  chemical  statics  are 
governed  by  the  law  of  mass  action  (law  of  Guldberg  and  Waage), 
as  well  as  by  the  nature  of  the  reacting  substances  and  the  tempera- 
ture. This  law  states  that  the  chemical  action  of  a  substance  taking 
part  in  a  chemical  reaction  is  proportional  to  its  active  mass  (likewise  the 
concentration  of  the  mass,  i.e.,  the  quantity  contained  in  unit  volume, 
for  example,  the  number  of  gram-molecules  of  the  reacting  substances 
contained  in  a  liter). 

The  chemical  transformation  of  many  substances  does  not  there- 
fore proceed  completely  to  new  substances,  when  the  existing  con- 
ditions are  such  that  the  newly  formed  substances  can  likewise  act 
on  one  another.    For  example,  if  the  two  compounds  AB  and  CD 


60  GENERAL  CHEMISTRY. 

only  react  to  form  the  compounds  AD  and  BC,  then  in  the  normal 
course  of  the  reaction  not  only  will  these  be  formed,  but  the  original 
substances  AB  and  CD  will  be  'present  in  the  system  or  structure 
(i.e.,  in  the  number  of  substances  which  take  part  in  the  reaction), 
since  A  has  affinity  for  B  as  well  as  for  D.  Since  these  affinities 
act  simultaneously,  the  system  comes  into  equilibrium  when  certain 
quantities  of  the  four  possible  compounds  have  been  formed. 

The  law  of  mass  action  shows  the  signification  of  the  concentration 
of  substances  on  the  progress  of  chemical  reactions,  lays  the  foundation 
for  the  investigation  of  chemical  statics  and  dynamics,  and  is  of  wide 
significance,  since  with  the  help  of  this  law,  with  proper  consideration 
of  the  nature  of  the  substances  involved,  the  temperature  and  pressure, 
it  is  possible  to  deduce  mathematically  tlie  relations  between  the  quan- 
tities of  the  reacting  substances  and  their  action  and  to  reach  important 
conclusions  in  respect  to  the  velocity  of  reactions  and  in  respect  to  chemical 
equilibrium. 

I.  Chemical  Statics. 

Chemical  statics  treats  of  the  equilibrium  relations  which  ensue 
after  a  chemical  reaction  has  proceeded  for  a  certain  period.  Since, 
according  to  the  law  of  mass  action,  the  tendency  with  which  a  sub- 
stance strives  to  undergo  transformation  increases  with  its  concen- 
tration, therefore  in  a  chemical  reaction,  as  a  result  of  the  decrease 
in  the  original  substances,  their  tendency  to  transformation  becomes 
constantly  weaker,  and  on  the  other  hand,  as  a  result  of  the  increase 
in  the  products,  their  tendency  to  produce  retransformation  becomes 
constantly  greater;  finally,  in  this  way  the  mutual  action  of  the  sub- 
stances will  cease,  since  now  the  products,  in  the  quantities  in  which 
they  have  formed,  will  have  a  tendency  to  again  reproduce  the 
original  substances.  The  chemical  reaction  therefore  comes  to  a 
standstill  before  it  is  completed,  that  is,  the  system  reaches  a  state 
of  equihbrium. 

Every  such  state  of  equiUbrium  is  really  not  to  be  considered 
as  a  static  but  as  a  dynamic  system,  since  the  transformation  of 
materials  does  not  cease  in  the  state  of  equilibrium,  but  the  tendencies 
in  both  directions  compensate  one  another,  so  that  as  a  result  no 
further  alteration  in  the  given  chemical  system  can  be  detected. 

The  state  of  equilibrium  can  therefore  be  considered  as  that 
state  in  which  the  velocities  of  reaction  on  both  sides  of  the  given 
system  have  become  equal,  and  from  this  it  follows  that  in  all  reac- 
tions which  lead  to  a  state  of  equihbrium  this  will  be  reached  irre- 


CHEMICAL  STATICS.  61 

spective  of  whether  the  reaction  starts  with  the  original  substances 
or  with  the  final  products. 

Those  reactions  which  lead  to  the  same  final  states,  whether  they 
start  with  the  original  substances  or  with  the  products,  are  called 
reversible  reactions.  They  are  denoted  by  substituting  the  symbol<=i 
for  the  symbol  =  in  the  equations  representing  the  reaction. 

If,  for  example,  an  alcohol  is  mixed  with  an  acid,  an  ester  and  water 
are  formed,  but  a  part  of  the  alcohol  and  the  acid  always  remains  un- 
altered (provided  that  neither  the  acid  nor  the  alcohol  are  present  in  very 
great  excess,  p.  62)  no  matter  how  long  the  action  is  permitted  to  con- 
tinue. The  quantities  of  ester  and  water  which  will  be  formed  are  de- 
pendent on  the  original  quantities  of  alcohol  and  acid  taken,  and  approach 
a  certain  limit  which  is  different  for  every  different  mixture.  The  same 
limit  is  reached  when  an  ester  and  water  are  brought  together  in  a  propor- 
tion which  is  equivalent  to  that  of  the  alcohol  and  acid.     For  example: 

CH3COOII+      C2H5OH     ;=±CH3COOC2H,4-HOH 
Acetic  acid  +  Ethyl  alcohol«=^  Acetic  ester  +  Water. 

If  finely  divided,  glowing  iron  (Fe)  and  water  vapor  (H2O)  are  al- 
lowed to  act  on  one  another  in  an  enclosed  space,  an  equilibrium  system 
results  which  always  contains  iron  and  water  vapor  in  addition  to  ferro- 
fenic  oxide  and  hydrogen:  3Fe  +  4H20<=±Fe304  +  4H^  The  same  system 
of  equilibrium  is  obtained  when  glowing  ferro-ferric  oxide  and  hydrogen 
are  heated  in  a  closed  vessel. 

However,  a  chemical  reaction  does  not  only  proceed  to  a  state 
of  equilibrium,  but  is  complete,  if  through  the  mutual  action  of  the 
reacting  substances  there  are  formed  insoluble  or  volatile  substances, 
since  in  such  cases  the  given  products  are  removed  from  the  sphere 
of  action,  so  that  the  same  reaction  wliich  causes  the  formation  of 
the  first  quantity  of  insoluble  or  volatile  substance  can  again  take 
place  until  the  reaction  is  complete. 

When  sodium  bicarbonate  (NaHCOg)  is  heated,  it  is  converted  com- 
pletely into  sodium  carbonate  (Na2C03)  if  the  carbon  dioxide  (COg) 
which'  is  formed  can  escape:  2NaHC03==Na2C03  + 002  +  1120.  How- 
ever, if  the  carbon  dioxide  is  prevented  from  escaping  a  state  of  equi- 
librium is  reached,  since  sodium  bicarbonate  wiU  be  again  partially  re- 
formed : 

2NaHC03^Na2C03  +  CO2  +  HgO. 

If  water  vapor  is  allowed  to  act  on  glowing  iron  in  an  open  tube  so 
that  the  hydrogen  formed  can  escape,  then  no  state  of  equilibrium  is 
reached,  but  the  reaction  is  complete:  3Fe+4H20=Fe304  +  4H2.  The 
case  is  the  same  when  hydrogen  is  allowed  to  act  on  glowing  ferro-ferric 
oxide:  Fe304+4H2=3Fe  +  4HOH,  since  in  this  case  the  resulting  water 
vapor  can  escape  (above).  The  quantities  of  solids  present  in  a  system 
exert  no  influence  on  the  final  state  of  equiUbrium,  since  the  alteration 


62  GENERAL  CHEMISTRY. 

in  concentration  of  solids  under  ordinary  conditions  is  too  insignificant; 
therefore  for  the  equilibrium  between  iron,  water,  ferro-ferric  oxide, 
and  hydrogen  it  is  immaterial  how  much  of  the  two  solid  substances 
iron  and  ferro-ferric  oxide  and  in  what  proportions  they  are  present. 

When  no  insoluble  or  volatile  substances  are  formed  it  is  also 
possible  for  the  reaction  to  be  complete  or  almost  complete,  if  a 
great  excess  of  one  of  the  reacting  substances  is  present. 

If  an  acid  and  an  alcohol  are  mixed  there  are  formed  water  and  an 
ester:  for  example,  CHgCOOH  +  CjHgOH^CIIaCOOC.Hs  +  HOH.  This 
reaction  at  ordinary  temperatures  reaches  a  state  of  equilibrium  very 
slowly,  but  if  the  substances  are  heated  in  a  closed  vessel  at  100°  then 
the  state  of  equilibrium  is  attained  after  several  hours.  The  propor- 
tion of  the  quantities  of  the  four  reacting  substances  present  at  any 
interval  until  the  final  state  is  reached  is  such  that  the  original  substances 
are  constantly  decreasing,  the  products  constantly  increasing.  If  the 
quantity  (i.e.,  the  concentration)  of  one  of  the  reacting  substances  is 
increased,  then  the  reaction  can  be  carried  as  desired  in  one  or  the  other 
direction  beyond  the  state  of  equilibrium.  For  example,  by  the  action 
of  much  acid  on  a  little  alcohol,  or  of  much  alcohol  on  a  little  acid,  the 
formation  of  ester  is  almost  complete,  and  on  the  other  hand  by  the 
action  of  much  water  on  a  little  ester  the  latter  is  almost  completely 
split  up  into  alcohol  and  acid. 

Most  chemical  reactions  involve  a  final  state  of  equihbrium; 
complete  retransformations  are  only  occasionally  encountered;  indeed 
in  the  latter,  in  most  cases,  the  reactions  come  to  a  stop  before  the 
limit  of  possible  transformation  is  reached,  although  the  quantities 
of  materials  which  remain  finally  unaltered  are  so  small  that  they 
escape  direct  notice. 

Concerning  complete,  non-reversible  reactions,  see  endothermic 
compounds,  p.  69. 

At  constant  pressure  (and  also  at  constant  volume),  on  an  increase 
in  temperature  a  shifting  of  the  equilibrium  takes  place  with  an 
increase  of  that  substance  of  the  system  whose  formation  takes 
place  with  the  absorption  of  heat.  At  constant  temperature  an 
increase  in  the  pressure  produces  a  shifting  of  the  equilibrium  to 
that  side  where  the  reaction  proceeds  with  a  decrease  in  volume 
(principle  of  variable  equilibrium). 

In  the  system  CaCOg  (sohd)<=±CaO  (solid) +CO2  (gas),  the  pressure 
remaining  constant,  an  increase  in  temperature  causes  an  increased 
splitting  up  of  the  calcium  carbonate  (CaCOJ  into  calcium  oxide  (CaO) 
and  carbon  dioxide  (COg).  On  the  other  hand,  an  increase  in  the  pres- 
sure at  constant  temperature  promotes  the  formation  of  calcium  car- 
bonate  until   the   original   pressure   is   again   established.     Salts   which 


CHEMICAL  STATICS.  63 

are  in  contact  with  their  saturated  solutions  are  dissolved  in  greater 
quantity  by  an  increase  in  pressure  if  the  total  volume  of  the  salt  and 
the  quantity  of  water  necessary  to  dissolve  it  is  greater  than  the  volume 
of  the  resulting  solution. 

Equilibrium  of  the  first  order,  namely,  that  in  which  only  one  sub- 
stance (constituent)  is  present,  from  the  ph3-sical  standpoint  is  that 
between  the  different  states  of  aggregation  of  a  substance,  e.g.,  between 
water  and  water  vapor,  between  ice  and  water  and  water  vapor;  from 
the  chemical  standpoint  it  is  that  which  occurs  when  complex  mole- 
cules split  up  into  simple  molecules  of  similar  composition,  e.g.,  N202<=±2NO. 

Equilibrium  of  the  second,  third,  etc.,  order,  namely,  when  two, 
three,  etc.,  substances  (constituents)  are  present,  from  the  physical 
standpoint  is  the  equilibrium  between  two,  three,  etc.,  substances  which 
can  form  a  physical  mixture  (p.  46)  with  one  another,  e.g.,  the  mixture 
of  two,  three,  etc.,  gases  or  liquids  with  one  another,  the  solution  of 
one,  two,  etc.,  .solid  substances  in  a  liquid;  from  the  chemical  stand- 
point the  equilibrium  which  occurs  from  the  action  of  two,  three,  etc., 
substances  on  one  another. 

As  substances  or  components  of  a  chemical  equilibrium  not  all  atoms 
or  atomic  complexes  can  be  considered  as  the  same,  but  only  the  smallest 
number  of  those  of  which  all  the  bodies  taking  part  in  the  equilibrium 
are  composed.  Therefore  the  system  N^04:^2N02  has  only  one  com- 
ponent, the  system  CaCOgi^iCaO+COg  only  two  components.  As  a 
general  rule  for  any  given  system  as  many  components  are  to  be  taken 
as  the  number  of  members  of  the  system  minus  one. 

Homogeneous  equilibrium  is  that  in  which  all  the  components 

form  a  physically  and  chemically  homogeneous  system,  e.g.,  as  gases, 

as  mixed  hquids,  as  solutions,  etc.     This  form  of  equilibrium  exists 

in   the   gaseous   chemical   systems    H20<=±H2+0    and    N20^<=^2N02, 

or  in  the  Uquid  chemical  system  C2HSOH+ CH3COOH^CH3COOC2H5+ 

HOH  (p.  61). 

The  existence  of  solid  solutions  (p.  49)  and  the  power  possessed 
by  solids  to  diffuse  into  other  soUds  (p.  46)  allow  the  assumption  that 
in  homogeneously  solidifying  mixtures  (e.g.,  in  alloys)  a  condition  of 
mutual  chemical  action  and  final  equilibrium  can  exist,  although  in 
such  cases  fhe  chemical  action  proceeds  so  slowly  that  it  has  been  im- 
possible to  measure  it  except  in  certain  individual  cases. 

Heterogeneous  or  non-homogeneous  equilibrium  is  that  in  which 
the  components  are  present  in  different  states  of  aggregation  and 
thus  form  a  heterogeneous  system.  It  is  represented  by  the  chemical 
system  CaCOg  (sohd)^CaO  (solid) +  CO2  (gas),  and  further  by  the 
physical  systems  KNO3  (sohd)^KN03  (dissolved),  H2O  (nquid)^H20 
(vapor),  H2O  (soUd)^H20  (liquid). 

Condensed  equilibrium  is  that  form  of  heterogeneous  equilibrium 
in  which  no  gaseous  components  are  present,  or  if  present  can  be 
neglected. 


64  GENERAL  CHEMISTRY. 

The  chemically  and  physically  homogeneous  parts  of  which  a 
heterogeneous  system  is  built  up  are  called  phases;  they  can  be  mechan- 
ically separated  from  one  another  and  the  separate  phases  can  be 
physical  mixtures  as  well  as  chemical  substances. 

For  example,  the  system  Water  +  Water  vapor  consists  of  two  phases, 
the  system  Ice  +  Water  +  Water  vapor  of  three  phases,  the  system  CaCOg 
(solid)?::±CaO  (solid) +CO2  (gas)  of  three  phases,  the  system  3Fe  (solid) 
+  4HOH  (vapor) ^ziFcgO^  (solid) +4H2  (gas)  of  three  phases,  since  the 
water  vapor  and  the  hydrogen  gas,  like  all  gases,  constitute  only  one 
phase,  since  they  represent  in  all  parts  chemically  and  physically  homo- 
geneous mixtures. 

The  degree  of  freedom  stands  in  a  definite  relation  to  the  phases  of 
a  heterogeneous  system.  By  degree  of  freedom  is  understood  the  con- 
ditions (i.e.,  pressure,  temperature,  and  volume  relations),  which  can 
be  optionally  chosen  without  thereby  altering  the  equiUbrium  of  the 
system.  For  example,  the  system  Water  +  Water  vapor,  consisting 
of  two  phases,  has  one  freedom,  namely,  either  the  pressure  or  the  tem- 
perature can  be  chosen  as  desired  without  altering  the  system.  If  the 
pressure  is  fixed  then  the  system  can  exist  only  at  a  perfectly  definite 
temperature,  if  the  temperature  is  fixed  then  the  system  can  exist  only 
at  a  perfectly  definite  pressure.  The  system  Ice  +  Water  +  Water  vapor, 
consisting  of  three  phases,  has  no  freedom  and  can  therefore  exist  only 
at  a  perfectly  definite  pressure  (4.6  mm.)  and  a  definite  temperature 
(  +  0.007°). 

Also  every  elementary  substance  has  two  freedoms  for  every  state  of 
aggregation,  i.e.,  of  its  three  variable  quantities,  pressure,  temperature, 
and  volume,  two  can  be  altered  as  desired  without  changing  the  state 
of  aggregation. 

Every  system  of  equilibrium  consisting  of  one  component  has  with  two 
phases  one  freedom,  with  three  pliases  no  freedom;  for  every  further 
component  the  number  of  freedoms  increases  by  one;  therefore  the 
system  CaC03?:±CaO+C02,  consisting  of  two  constituents  fp.  62)  and  > 
three  phases  (above),  has  one  freedom.  Hence  follows  the  phase  rule  of 
Gibbs:  Equilibrium  exists  when  the  sum  of  the  phases  (P)  and  the  degrees  of 
freedom  (F)  of  a  system  is  equal  to  tv)o  m^re  than  the  comrtonents  (B)  (see 
p.  63^,  that  is,  when  P+F=B  +  2. 

With  the  assistance  of  the  phase  rule,  the  number  of  degrees  of  freedom 
on  the  one  hand,  and  the  number  of  phases  on  the  other,  which  for  the 
given  components  of  a  system  must  be  present  in  a  state  of  equilibrium, 
can  be  readilj'^  calculated  beforehand,  since  F  =  B  4-  2  —  P  and  P=  B  +  2  —  F. 
From  the  latter  it  follows:  If  a  heterogeneous  system  is  in  a  state  of 
complete  equilibrium  then  one  phase  more  must  be  present  than  the 
number  of  the  components,  if  more  phases  are  present  then  equilibrium 
of  the  separate  phases*  is  only  possible  at  a  definite  temperature,  pressure, 
and  concentration.  If  less  phases  are  present,  then  the  equilibrium  is 
incomplete. 

All  systems  of  equilibrium  with  equal  degrees  of  freedom  show  com- 
plete agreement  in  their  behavior  if  the  factors  (i.e.,  pressure,  tempera- 
ture, or  volume),  which  influence  the  equilibrium,  arc  allowed  to  con- 
tinuously alter.  Since  the  degree  of  freedom  can  be  calculated  with 
the  help  of  the  phase  rule,  this  rule  also  serves  for  dividing  systems  of 


CHEMICAL  KINETICS.  65 

equilibrium  according  to  the  number  of  their  degrees  of  freedom  into 
non-,  uni-,  di-,  etc.,  variant  systems.  The  system  of  equiUbrium  con- 
sisting of  Water  vapor  +  Water  +  Ice,  which  can  coexist  only  at  0.007° 
and  4.6  mm.  pressure,  is  a  nonvariant  system;  this  system  has  one  compo- 
nent and  three  phases,  therefore  F  =  l+2  — 3=0.  Neither  the  pressure 
nor  temperature  can  be  altered  without  destroying  the  system. 

A  monovariant  system  is  represented  by  CaCOg  (solid);=iCaO  (solid)  + 
CO2  (gas) ,  since  it  has  2  components  and  3  phases,  namely,  =2  +  2  —  3  =  1; 
if  the  temperature  is  varied,  then  for  every  given  temperature,  the  pres- 
sure under  which  the  system  stands  is  a  perfectly  definite  pressure,  or 
if  the  pressure  is  varied,  then  a  definite  temperature  corresponds  to 
every  given  pressure. 

The  number  of  phases  present  in  a  heterogeneous  system  of  equi- 
librium can  be  determined  with  the  assistance  of  the  phase  rule,  which  is 
of  importance  in  those  cases  in  which  the  nature  of  the  phases  cannot  be 
determined  by  direct  observation.  For  example,  metallic  palladium 
absorbs  large  quantities  of  hydrogen  and  it  is  a  difficult  matter  to  tell 
whether  a  chemical  compound,  PdgH,  or  a  solid  solution  is  formed.  In 
the  case  of  chemical  combination,  owing  to  partial  decomposition,  there 
would  exist  a  system  of  equilibrium,  viz.,  PdgH  (solid)?=±Pd2  (solid) +H 
(gas),  comprising  2  components  and  3  phases.  According  to  this  the 
degree  of  freedom  would  be  2  +  2  —  3  =  1,  which  is  contrary  to  fact. 
Therefore  a  solid  solution  and  not  a  chemical  compoimd  must  be  formed 
in  this  process. 

2.  Chemical  Kinetics. 

Chemical  kinetics  treats  of  the  rate  of  progress  of  chemical  reac- 
tions (the  velocity  of  reaction),  namely,  the  ratio  of  the  quantities 
(calculated  in  gram-molecules)  of  substance  transformed  to  the  time 
required  for  the  process. 

The  velocity  of  reaction  depends  on  the  nature  of  the  substances, 
the  temperature  of  the  reacting  mixture,  and  the  quantities  of  the 
reacting  substances  (namely,  their  concentration,  p.  59),  but  the 
pressure  (except  in  the  presence  of  gases)  does  not  come  into  con- 
sideration. 

All  chemical  reactions  have  the  same  general  characteristic  with 
respect  to  the  velocity  of  reaction  in  that  they  begin  with  the  greatest 
velocity  and  that  this  becomes  constantly  smaller. 

Temperature  increases  the  velocity  of  reaction. 

The  heating  of  many  organic  substances  which  are  to  be  combined 
is  carried  out  in  closed  vessels  in  order  that  the  substances  may  be  re- 
tained in  a  liquid  condition  even  at  such  high  temperatures  by  the  result- 
ing pressure  and  in  order  that  the  velocity  of  reaction  may  be  sufficiently 
great. 

The  influence  of  temperature  cannot  be  explained  simply  on 
the  assumption  that  an  increase  in  this  causes  the  molecules  of  the 


66  GENERAL  CHEMISTRY. 

reacting  substances  to  encounter  each  other  more  frequently,  since 
this  molecular  movement  in  gases,  and  apparently  also  in  liquids, 
at  the  average  temperature  increases  only  about  ^  per  cent,  for  every 
degree  of  heat,  while  the  actual  increase  of  the  velocity  of  reaction 
for  every  degree  is  10-12  per  cent.  An  explanation  of  this  phenomenon 
has  not  yet  been  discovered. 

The  velocity  of  reaction  differs  greatly.  It  is  very  great  in  the 
case  of  the  formation  of  salts  in  aqueous  solutions  (since  this  is  a 
reaction  between  ions,  p.  83) ;  in  the  case  of  the  formation  and  decom- 
position of  organic  compounds  it  is  so  much  slower  that  it  can  be 
readily  followed  quantitatively.  This  is  also  the  case  in  chemical 
reactions  in  gases  when  the  temperature  employed  is  not  too  high. 
On  the  other  hand,  for  example,  hydrogen  and  oxygen  act  so  slowly 
on  one  another  at  ordinary  temperature  that  a  measurement  of  the 
velocity  of  reaction  is  impossible.  In  such  cases  it  is  possible,  by 
raising  or  lowering  the  temperature,  so  to  alter  the  conditions  of 
experiment  that  the  velocity  is  brought  within  the  range  of  measure- 
ment. 

In  many  cases  the  presence  of  certain  substances  has  an  accelerat- 
ing or  retarding  action  on  the  velocity  of  reaction,  although  these 
substances  apparently  do  not  take  part  in  the  chemical  change. 
This  action  is  called  catalytic  action  and  the  substances  are  called 
catalytic  agents  (p.  9).  There  are  special  catalytic  agents  which 
are  only  active  in  the  case  of  certain  reactions,  and  general  cata- 
lytic agents  of  which  the  acids  are  the  most  conspicuous  examples. 
Practically  all  slowly  proceeding  reactions  are  accelerated  by  the 
presence  of  small  quantities  of  acids,  provided  that  the  acid  does 
not  combine  with  one  of  the  reacting  substances.  Catalytic  agents 
play  an  important  part  not  only  in  technical  chemistry  but  also  in 
biology  (see  Ferments). 

Up  to  the  present  the  velocity  of  reaction  has  been  investigated 
chiefly  for  chemical  reactions  in  homogeneous  systems  (p.  63),  while 
in  heterogeneous  systems  (p.  63),  where  it  is  dependent  on  the  size  and 
character  of  the  contact-surfaces,  in  addition  to  the  temperature,  and 
on  other  conditions  (e.g.,  the  diffusion),  it  still  offers  great  difficulties. 

If  a  chemical  reaction  proceeds  not  only  to  a  state  of  equilibrium, 
but  as  almost  or  quite  complete,  then,  in  general,  after  a  time  which  is 
ten  times  as  great  as  that  required  for  the  reaction  to  become  half  com- 
pleted, the  still  unaltered  portion  of  the  system  will  have  sunken  to 
a  quantity  which  is  no  longer  measurable.  In  such  reactions  the  only 
factor  which  comes  into  consideration  is  the  velocity  of  reaction  of  the 


THERMOCHEMISTRY,  67 

original  substances,  which  in  every  moment  is  proportional  to  the  product 
of  the  concentration  (the  active  mass)  of  the  still  undecomposed  original 
substances  and  a  constant  coefficient  of  velocity,  which,  however,  has  a 
different  value  for  mono-,  di-,  tri-,  etc.,  molecular  reactions  (i.e.,  for  reac- 
tions which  can  be  considered  as  proceeding  from  one,  two,  three,  etc., 
molecules). 

With  the  help  of  the  coefficient  of  velocity  it  can  be  determined 
"whether  a  reaction  is  monomolecular  or  dimolecular  or  trimolecular,  etc. 
For  example,  is  the  assumption  correct  that  the  decomposition  of  arseniu- 
retted  hydrogen  is  a  tetramolecular  reaction,  since  the  separated  arsenic 
in  a  solid  state  contains  at  least  four  atoms  in  the  molecule  (p.  21): 
4ASH3  =  AS4  +  6H2;  the  determination  of  the  velocity  coefficient  gives 
a  result  which  corresponds  to  a  monomolecular  reaction.  The  reaction 
must  therefore  proceed  as  follows:  AsH3=As  +  H3,  so  that  each  molecule 
first  splits  into  its  atoms  and  then  two  hydrogen  atoms  combine  to  form 
a  hydrogen  molecule  and  the  unknown  number  of  arsenic  atoms  combine 
to  form  an  arsenic  molecule  of  the  solid  arsenic. 

If  a  chemical  reaction  proceeds  only  to  a  state  of  equilibrium,  then 
in  this  state  the  velocity  of  reaction  must  have  become  equally  great 
on  both  sides  of  the  system,  namely,  in  this  state  the  original  substances 
of  the  reaction  nmst  combine  just  as  fast  as  the  products  react  on  each 
other  to  form  the  original  materials.  For  example,  if  one  gram-molecule 
of  alcohol  and  acetic  acid  are  mixed,  then  a  state  of  equilibrium  results 
just  as  soon  as  two-thirds  of  the  total  quantity  of  ethyl  acetate,  which 
would  be  formed  if  the  reaction  was  complete,  has  been  produced. 
In  this  case  neither  the  velocity  of  the  transformation  of  the  original 
materials  nor  the  simultaneous  transformation  of  the  products  can  be 
measured,  but  this  process  can  be  considered  as  if  the  opposed  reactions 
proceeded  independently  of  one  another  (principle  of  coexistence);  the 
difference  of  these  two  velocities  can  be  measured,  since  it  must  corre- 
spond to  the  velocity  with  which  the  reaction  approaches  the  state  of 
equilibrium.  Since  the  chemical  change  observed  in  every  moment  of 
time  is  equal  to  the  change  in  one  direction  diminished  by  the  change 
in  the  other  direction,  therefore  by  determining  this  difference  the  dif- 
ference in  the  velocities  of  reaction  can  be  arrived  at.  For  example, 
the  quantity  of  ethyl  acetate  formed  in  every  moment  of  time  from 
acetic  acid  and  ethyl  alcohol  can  be  m<'asured,  and  likewise  the  quantity 
of  ethyl  alcohol  and  acetic  acid  formed  from  ethyl  acetate  and  water. 
From  the  difference  of  the  quantities  formed  in  both  cases  the  product 
of  the  velocity  of  reaction  can  be  calculated. 

THERMOCHEMISTRY 

is  the  study  of  the  relation  between  chemical  energy  and  heat; 

I.  General. 

Of  all  transformations  of  chemical  energy  into  other  forms  of 
energy,  the  transformation  into  heat  proceeds  the  most  readily. 
The  production  or  absorption  of  heat  (and  often  at  the  same  time  of 
other  forms  of  energy)  accompanies  all  chemical  reactions. 


68  GENERAL  CHEMISTRY, 

The  changes  in  energy  consisting  in  the  absorption  and  production 
of  heat  supply  important  explanations  of  the  course  of  a  reaction  and 
the  manner  of  formation,  stability,  and  nature  of  the  resulting  com- 
pounds. However,  on  the  combination  of  substances  which  show  the  great- 
est affinities  (p.  6)  for  one  another  it  is  by  no  means  true  that  the  great- 
est quantities  of  heat  are  set  free,  but  the  quantity  of  heat  set  free  depends 
also  on  the  change  in  the  state  of  the  substances  which  take  part  in  the 
given  chemical  process.  Therefore  the  quantity  of  heat  produced 
or  absorbed  in  a  chemical  process  cannot,  as  was  formerly  assumed, 
serve  as  a  measure  of  the  affinity  of  the  given  substances 

According  to  whether  heat  is  produced  or  absorbed  in  a  chemical 
reaction  the  reaction  is  called  exothermic  or  endothermic.  Similarly 
a  substance  is  called  exothermic  or  endothermic  according  to  whether 
in  its  formation  heat  is  set  free  or  absorbed.  Exothermic  changes 
are  positive  heat  reactions,  endothermic  are  negative  heat  reactions. 
The  heat  is  measured  in  heat-units  or  calories,  a  large  calorie  ( =  Cal.) 
being  the  quantity  of  heat  required  to  warm  1  kilogram  of  water  1°, 
a  small  calorie  ( =  cal.)  the  quantity  of  heat  required  to  warm  1  gram 
of  water  1°. 

In  order  to  allow  the  simplest  comparison  the  heat  is  calculated,  not 
on  the  basis  of  the  gram-unit,  but  on  the  basis  of  the  gram-quantity 
corresponding  to  the  number  of  atoms  which  combine  to  form  a  mole- 
cule. The  heat  values  are  mostly  based  on  the  state  in  which  the  sub- 
stances exist  at  18° 

The  heat  is  distinguished  as  the  heat  of  solution,  the  heat  of  dilution, 
the  heat  of  formation,  the  heat  of  decomposition,  the  heat  of  neutrali- 
zation, and  the  heat  of  combustion;  further,  as  the  heat  of  hydration 
(i.e.c  the  heat  which  results  on  the  combination  of  a  substance  with  a 
definite  number  of  water  molecules)  and  as  the  heat  of  dissociation  (i.e., 
the  heat  which  results  from  the  splitting  up  of  a  dissolved  substance  into 
its  ions).  The  heat  calculated  on  the  basis  of  the  gram-molecule  of  the 
given  substance  is  called  the  molecular  heat  of  solution,  heat  of  forma- 
tion, etc. 

The  mixing-calorimeter  is  used  in  measuring  the  heat  in  liquids  or 
solutions.  It  consists  of  a  vessel  of  metal  or  glass  in  which  the  react- 
ing substances  are  mixed,  their  temperature  having  been  accurately 
measured  beforehand.  The  quantity  of  heat  is  calculated  from  the 
alteration  in  temperature  which  is  produced  in  the  quantity  of  water 
present,  this  having  been  carefully  measured. 

The  combustion-calorimeter  serves  for  measuring  the  heat  produced 
in  combustions.  It  consists  of  a  tightly  closed  steel  sphere  (calorimetric 
bomb)  lined  on  the  interior  with  platinum  or  enamel.  Within  this  the 
substance  under  investigation  is  placed  and  the  bomb  is  filled  with  oxygen 
under  a  pressure  of  about  25  atmospheres.  The  substance  is  then  ignited 
by  a  wire  brought  to  incandescence  by  an  electric  current  and  is  burned. 
The  quantity  of  heat  produced  is  calculated  from  the  elevation  in  the 
temperature  of  the  water  with  which  the  steel  sphere  is  surrounded. 


THERMOCHEMISTRY,  69 

Exothermic  compounds  contain  less  energy  than  their  compo- 
nents and  are  therefore,  at  ordinary  temperatures,  more  stable  than 
these.  Their  formation,  having  been  once  started,  proceeds  with- 
out the  further  addition  of  heat  (energy)  from  without  (p.  59)  with 
greater  or  less  velocity,  depending  on  the  quantity  of  heat  developed. 
The  violence  of  the  formation  can  in  some  case  be  such  as  to  cause 
an  explosion  (for  example,  the  formation  of  water  from  Hj+O,  of 
HCl  from  H+Cl).  The  decomposition  of  exothermic  compounds 
requires  the  continuous  addition  of  heat  (or  other  form  of  energy) 
and  is  therefore  an  endothermic  reaction;  it  proceeds  slowly,  never 
with  an  explosion,  and  is  limited  by  the  opposing  tendency  of  the 
components  to  again  enter  into  combination,  since  these  components, 
because  of  the  absorption  of  heat,  are  more  energetic  than  the  original 
compound  and  can  combine  to  produce  this  (see  Dissociation). 

Endothermic  compounds  contain  more  energy  than  their  com- 
ponents and  can  therefore  more  or  less  readily  split  up  into  them. 
Their  formation  proceeds  only  slowly  with  the  continuous  addition 
of  heat  (or  other  form  of  energy)  from  without.  As  a  result  of  the 
elevation  in  temperature  the  combination  often  takes  place  only 
partially,  owing  to  the  tendency  of  the  resulting  compound  to  break 
down  again  into  its  components.  The  decomposition  of  endothermic 
compounds  does  not  require  the  addition  of  heat  (or  other  form  of 
energy),  but  needs  only  an  external  stimulus  in  order  to  spontane- 
ously proceed  both  rapidly  and  completely  (often  so  rapidly  that  an 
explosion  results,  p.  73)  with  the  evolution  of  heat.  The  decom- 
position is  therefore  an  exothermic  reaction,  and  the  decomposition 
products  formed  cannot  of  themselves  again  combine  when  the 
temperature  is  lowered,  since,  because  of  the  evolution  of  heat,  they 
are  poorer  in  energy  than  the  original  compound.  This  explains 
the  existence  of  many  non-reversible  reactions. 

Every  compound  has  a  certain  heat  of  formation  which  is  equal  to 
its  heat  of  decomposition  (Law  of  Lavoisier  and  Laplace).  If  2.02 
grams  of  hydrogen  and  16  grams  of  oxygen  combine  to  form  water, 
a  quantity  of  heat  equal  to  68  Cal.  is  set  free:  2H+0  =H20+68  Cal., 
while  126.8  grams  of  iodine  and  1.01  grams  of  hydrogen  combine  with 
an  absorption  of  heat  equal  to  6  Cal.:  I+H=HT-6  Cal.  If  one 
molecule  of  water  ( =  18  grams)  is  decomposed  into  its  elements,  then 
the  quantity  of  heat  evolved,  equal  to  68  Cal.,  must  be  again  added 
to  it,  which  is  then  contained  as  chemical  energy  in  the  elements 


70  GENERAL  CHEMISTRY. 

(molecules)  which  are  set  free:  H20  =  H2+0  — 68  Cal.,  while  in  the 
decomposition  of  1  molecule  of  hydrogen  iodide  ( =  127.8  grams)  an 
evolution  of  heat  equal  to  6  Cal.  takes  place:  HI  =H+l4-6  Cal. 

Equations  which  include  the  energy  set  free  or  absorbed,  meas- 
ured in  the  form  of  heat,  are  called  thermochemical  equations. 

The  evolution  of  heat  which  accompanies  a  chemical  process  is 

always  the  same  whether  the  process  takes  place  in  one  step  or  whether 

it  passes  through  a  number  of  intermediate  processes  (Law  of  Hess). 

For  example,  on  dissolving  39  grams  of  potassium  in  36.4  grams  of 
dissolved  hydrochloric  acid  a  quantity  of  heat  equal  to  61.8  Cal.  is 
evolved,  and  the  final  result  is  the  same  whether  the  process  takes  place 
in  one  step:  K  +  HC1  =  KC1  +  H  +  61.8,  or  whether  it  takes  place  in  two 
reactions:  K  +  ILO=KOH  +  H  +  41.8  Cal.  and  K0H  +  HC1  =  KC1  + 
H2O  +  I3.7  Cal.  The  law  is  very  important,  since  it  makes  it  possible 
to  calculate  the  heat  in  many  cases  where  it  cannot  be  determined 
directly;  for  example,  the  heat  of  formation  of  carbon  monoxide  (CO) 
=26.3  Cal.  is  deduced  from  the  combustion  of  carbon  to  carbon  dioxide: 
C  +  20=C02  +  94.3  Cal,  and  from  the  combustion  of  carbon  monoxide 
to  carbon  dioxide:  CO +  0=00,+ 68  Cal;  therefore  94.3  Cal  -68  Cal  = 
26.3  Cal 

In  many  chemical  reactions  there  is  a  tendency  to  produce  those 
substances  whose  formation  is  accompanied  by  the  evolution  of 
the  greatest  quantity  of  heat  (principle  of  maximum  work).  For 
example,  in  a  system  consisting  of  potassium +chlorine+ bromine 
potassium  chloride  (KCl)  and  not  potassium  bromide  (KBr)  is  formed, 
since  K+Br  =  KBr+90  Cal;    K+C1=KC1+106  Cal 

Accordingly,  a  chemical  reaction  generally  takes  place  more  readily 
if  the  resulting  products  have  an  opportunity  to  enter  into  a  second 
reaction,  since  in  this  case  a  greater  quantity  of  heat  is  produced.  For 
example,  chlorine  decomposes  water  only  very  slowly:  H.p  +  2C1  = 
2HC1  +  O  +  10  Cal;  but  if  the  oxygen  can  immediately  exert  a  further 
chemical  action  (as  is  the  case,  for  example,  in  the  presence  of  sulphur 
dioxide  (SO,),  then  a  rapid  decomposition  of  the  water  takes  place 
2H20  +  2Cl  +  S02  =  H2SO,  +  2HCl  +  74  Cal 

The  principle  of  maximum  work  has  not  the  universal  application 
which  was  at  first  attributed  to  it;  it  applies  to  such  reactions  as  proceed 
at  ordinary  conditions  of  temperature  and  pressure  and  to  such  sub- 
stances as  are  stable  under  increase  in  temperature.  It  does  not  apply 
at  high  temperatures;  indeed  under  such  conditions  the  contrary  is  gen- 
erally true  and  endothermic  compounds  are  formed,  as  is  illustrated 
by  the  many  dissociation  phenomena  (see  below). 

2.  Transformation  of  Heat  into  Chemical  Energy. 
This  occurs  on  the  formation  of  endothermic  compounds  and  on 
the  decomposition   of  exothermic   compounds  by  the  addition   of 
heat.    The  latter  is  a  dissociation  phenomenon. 


THERMOCHEMISTRY,  71 

Dissociation  is  the  name  applied  to  the  splitting  up  of  the  mole- 
cules of  certain  substances  into  simpler  constituents  which  takes 
place  under  certain  favorable  conditions.  Dissociation  exists  only 
so  long  as  the  dissociating  influences  are  acting;  when  they  cease 
the  dissociation  products  again  combine  to  form  the  original  sub- 
stances. 

A  distinction  is  made  between  the  thermal  dissociation  produced 
by  heating,  which  for  short  is  called  dissociation,  and  that  which 
appears  on  the  solution  of  certain  substances,  the  electrolytes,  which 
is  known  as  electrolytic  and  hydrolytic  dissociation  (p.  77). 

Thermal  dissociation  does  not  appear  suddenly  in  the  whole 
quantity  of  the  given  substance,  but  begins  gradually,  and  steadily 
increases  with  increasing  temperature.  With  decreasing  tempera- 
ture the  recombination  of  the  dissociation  products  proceeds  simi- 
larly. 

For  example,  hydrogen  and  oxygen  begin  to  combine  to  form  water 
vapor  (HgO)  at  200°,  but  at  1^00°"  a  splitting  up  of  the  water  into  the 
two  elements  begins.  At  2500°  half  of  the  water  is  dissociated  and 
finally  with  increasing  temperature  all  of  the  water  is  split  up  and  the 
two  elements  exist  side  by  side,  as  at  200°.  If  the  temperature  is  now 
lowered  the  formation  of  water  again  takes  place:  H20:«=*2H  +  0,  and 
at  1200°  the  elements  have  again  completely  combined  with  one  another. 

Crystallized,  anhydrous  sulphuric  acid  (HgSOJ  even  at  40°  begins 
to  split  up  into  sulphur  trioxide  (SO3)  and  water  (HjO);  this  dissocia- 
tion is  complete  at  416°;  on  cooling  the  combination  of  the  dissociation 
products  gradually  takes  place. 

The  dissociation  phenomena  constitute  a  class  of  reversible  reac- 
tions (p.  61),  and  at  constant  pressure  (see  below)  for  every  given 
temperature  the  degree  of  dissociation  of  a  substance  is  perfectly 
definite,  so  that  a  definite  state  of  equilibrium  exists  between  the 
undecomposed  substance  present  and  its  decomposition  products. 

If  a  closed  vessel  filled  with  hydrogen  iodide  (HI)  is  heated  to  518°, 
then  21  per  cent,  of  the  gas  dissociates  into  H  +  I.  If  quantities  of  H  +  I 
corresponding  to  their  atomic  weights  are  heated  in  a  closed  vessel  to 
515°,  then  21  per  cent,  of  the  gaseous  mixture  remains  uncombmed,  while 
the  remainder  is  transformed  into  HI  gas :  2HI«=>2H  4-  21. 

If  the  dissociation  takes  place  with  an  increase  in  volume,  which 
is  usually  the  case,  then  it  is  dependent  on  the  pressure  as  well  as  on 
the  temperature.  If  the  pressure  is  increased  the  dissociation  de- 
creases, if  the  pressure  is  lowered  then  the  dissociation  increases. 
For  every  given  pressure  (the  dissociation  pressure  or  dissociation 


•^  GENERAL  CHEMISTRY. 

tension)  the  degree  of  dissociation  of  a  substance  at  constant  tem- 
perature has  a  definite  value,  so  that  a  state  of  equihbrium  exists 
also  at  the  given  pressure. 

Hydrogen  iodide  when  sufficiently  heated  dissociates  without  increase 
in  volume:  2HI=2H  +  21  (2  molecules  (4  volumes)  =2  volumes  +  2  vol- 
umes), so  that  on  heating  this  substance  to  518°  (see  above)  the  dis- 
sociation will  be  only  21  per  cent,  whether  the  pressure  be  increased 
or  lowered.  When  barium  dioxide  (BaOg)  is  heated  to  700°  at  reduced 
pressure  it  completely  dissociates  into  barium  oxide  and  oxygen,  BaOg  = 
BaO  +  0,  which  causes  an  increase  in  volume.  Under  sufficiently  high 
pressure,  however,  at  the  same  temperature  barium  oxide  combines 
completely  with  oxygen  to  form  barium  dioxide. 

The  abnormal  (i.e.,  apparently  contradictory  to  Avogadro's 
law)  gas  densities  which  many  substances  show  by  exhibiting  in  a 
gaseous  state  a  smaller  specific  gravity  (= vapor  density,  p.  43)  than 
corresponds  to  their  molecular  weights,  as  determined  by  chemical 
methods,  are  due  to  dissociation  phenomena.  Such  substances,  on 
being  converted  into  gases,  suffer  a  more  or  less  complete  dissocia- 
tion into  simpler  molecules  or  even  into  atoms,  as  a  result  of  which 
at  a  constant  pressure  the  volume  is  increased  (in  proportion  to 
Gay-Lussac's  law,  p.  15)  and  the  specific  gravity  correspondingly 
diminished,  or  if  the  volume  remains  constant  the  pressure  on  the 
surrounding  walls  is  increased.  For  example,  the  vapor  density  of 
iodine  at  600°  =  127,  corresponding  to  the  molecular  weight  l2  =  254; 
above  600°  this  value  decreases  steadily  and  at  15(X)°  has  only  half 
the  value  and  then  remains  constant.  This  is  explained  by  the 
gradual  splitting  up  of  the  iodine  molecule  Ij  into  the  free  atoms  I+I. 

The  vapor  density  of  sulphur  at  190-300°  is  128,  at  500°  it  is  96, 
but  at  1000°  it  becomes  constant  and  then  has  the  value  64.  Since 
the  atomic  weight  of  sulphur  is  32  and  the  molecular  weight  at  190- 
300°  is  256,  the  molecule  at  this  temperature  contains  8  atoms.  At 
500°  the  molecular  weight  is  192  and  the  molecule  contains  6  atoms. 
At  1000°  the  molecular  weight  is  64  and  the  molecule  therefore  contains 
2  atoms. 

The  increase  in  the  number  of  atoms  in  the  molecules  of  certain  ele- 
ments when  the  temperature  is  lowered  makes  it  appear  probable  that 
many  elements  in  the  liquid  or  solid  state  contain  more  atoms  in  the 
molecule  than  when  in  the  gaseous  condition. 

Through  the  alteration  in  the  volume  and  the  specific  gravity 
(vapor  density)  of  a  gaseous  substance  it  is  possible  to  calculate 
the  degree  of  dissociation. 

For  example,*  the  specific  gravity  of  vaporized  ammonium  chloride 
(NH^Cl)  does  not  correspond  to  its  molecular  weight =53.4  (p.  43),  but 


THERMOCHEMISTRY.  73 

is  only  equal  to  26. 7;  therefore  the  complete  dissociation  of  the  molecuk 
NH^Cl  (=2  vols.)  into  one  molecule  of  NH3  (=2  vols.)  and  one  mole^ 
cule  HCl  (  =  2  vols.)  has  taken  place,  and  a  doubling  of  the  volume  and 
a  corresponding  reduction  in  the  specific  gravity  to  the  half  of  that  which 
would  agree  to  the  molecule  NH^Cl  is  produced. 

In  order  to  explain  the  dissociation  it  is  assumed  that  this  is  caused 
not  only  by  the  molecular  motion  (p.  59),  but  also  by  the  motion  of 
the  atoms  within  the  molecule;  on  warming  both  motions  are  increased 
and  finally  the  atomic  vibrations  are  so  violent  that  the  atoms  are  sep- 
arated from  one  another  and  the  molecules  finally  break  up  into  atoms. 
Moreover  at  any  given  temperature,  as  a  result  of  the  irregularity  of 
the  encounters  of  the  molecules,  all  of  the  molecules  will  not  have  the 
same  velocity;  those  which  move  the  most  rapidly  will  be  the  warmer, 
those  which  move  the  slowest  will  be  the  cooler,  and  therefore  the  dis- 
sociation is  gradual  and  increases  with  the  temperature,  since  the  disso- 
ciation only  occurs  among  the  more  highly  heated  molecules,  the  number 
of  which  increases  with  the  temperature. 

Concerning  the  acceleration  of  chemical  processes  by  heat  see 
Chemical  Kinetics,  p.  65. 

Concerning  the  shifting  of  the  equilibrium  by  heat  see  Chemical 
Statics,  p.  62. 

3.  Transformation  of  Chemical  Energy  into  Heat 

This  takes  place  on  the  formation  of  exothermic  compounds 
and  on  the  decomposition  of  endothermic  compounds;  frequently 
during  these  processes  a  portion  of  the  resulting  heat-energy  is  con- 
verted into  radiant  energy  (p.  91). 

The  evolution  of  heat  on  the  formation  of  exothermic  compounds 
and  on  the  decomposition  of  endothermic  compounds  can  sometimes 
take  place  w^ith  great  velocity  and  with  the  development  of  great 
pressure  (as  a  result  of  the  expansion  by  heat  of  the  gases  present 
before  or  after  the  reaction).     This  is  called  an  explosion. 

The  mechanical  action  of  an  explosion  is  strongest  when  it  is  pro- 
duced by  the  decomposition  of  a  solid  or  liquid  substance,  since  in  such 
cases  the  resulting  gases  occupy  a  much  greater  volume  with  respect 
to  the  exploding  substance  than  when  this  is  already  gaseous  before 
the  explosion  (see  Water,  Gunpowder,  Glycerine  Nitrates,  and  Cellulose 
Nitrates). 

If  the  chemical  reaction  is  once  started  at  any  one  point  the 
formation  of  exothermic  compounds  and  the  decomposition  of  endo- 
thermic compounds  proceeds  without  the  addition  of  any  further 
heat  (or  other  form  of  energy)  if  the  heat  resulting  from  the  reaction 
is  sufficient  to  raise  the  temperature  of  the  neighboring  parts  to  the 
temperature  of  ignition.     If,  however,  the  heat  at  first  produced  ia 


74  GENERAL  CHEMISTRY. 

removed  by  radiation  or  conduction  more  rapidly  than  it  can  be 
transmitted  to  the  neighboring  parts  (see  Combustion),  then  the 
reaction  apparently  ceases,  since  the  velocity  of  reaction  assumes  a 
minimum  value  (p.  66). 

In  general  exothermic  compounds  are  stable  on  heating,  exposure  to 
shock,  etc.,  and  this  stability  increases  the  greater  the  heat  of  formation. 
Water  vapor  and  hydrogen  chloride  gas,  whose  heats  of  formation  are +  68 
Cal.  and  +22  Cal,  respectively,  are  completely  dissociated  only  at  very 
high  temperatures  and  not  at  all  affected  by  pressure,  shock,  etc.  En- 
dothermic  compounds,  on  the  contrary,  are  mostly  unstable.  Nitrogen 
chloride,  whose  heat  of  formation  is  —38  Cal.,  decomposes  into  chlorine 
and  nitrogen  under  the  slightest  disturbing  influence.  Many  endothermic 
compounds,  however,  are  in  most  cases  stable.  For  example,  acetylene 
gas,  although  its  heat  of  formation  is  —58  Cal,  can  nevertheless  be  sub- 
jected to  many  manipulations  without  undergoing  decomposition.  It 
has,  however,  been  observed  in  the  case  of  this  substance  that  it  is  un- 
stable when  acted  upon  simultaneously  by  a  sudden  high  pressure  and 
a  high  temperature. 

ELECTROCHEMISTRY 

is  the  study  of  the  relation  between  electrical  energy  and  chemical 
energy. 

I.  Transformation  of  Electrical  Energy  into  Chemical  Energy. 

The  electric  arc  and  spark  discharge  can  cause  chemical  com- 
bination or  decomposition,  but  judging  from  all  appearances  this  is  due 
only  to  the  heat  evolved  or  from  the  mechanical  disturbance  produced. 

The  electric  current,  on  the  contrary,  causes  only  chemical  decom- 
position (and  spatial  separation,  p.  77),  which  occurs  when  it  is 
allowed  to  pass  through  a  conductor  of  the  second  order.  This 
phenomenon  is  called  electrolysis  {y\vevv^  to  loosen)  and  it  can  be 
very  diversified. 

Conductors  of  the  first  order  are  those  substances  which  conduct 
electricity  without  undergoing  decomposition;  e.g.,  metals,  per- 
oxides, carbon,  selenium. 

Conductors  of  the  second  order  or  electrolytes  are  those  substances 
which  conduct  electricity  only  by  undergoing  a  simultaneous  chem- 
ical alteration.  To  this  class  belong  acids,  bases,  and  salts  when 
they  are  fused  or  dissolved  in  water. 

Non-conductors  or  non-electrolytes  are  substances  which  permit  no 
passage,  or  only  a  very  slight  passage,  of  electricity.  To  non-con- 
ductors belong  the  aqueous  solutions  of  organic  compounds  with 


ELECTROCHEMISTRY,  75 

the  exception  of  the  typical  organic  acids,  bases,  and  salts,  as  well 
as  the  solutions  of  almost  all  substances  in  the  greater  number  of 
organic  solvents. 

Electrodes  {68 6i^  path)  is  the  name  given  to  those  conductors 
of  the  first  order  through  which  the  electricity  enters  and  leaves  in 
the  electrolysis  of  the  conductors  of  the  second  order.  The  electrode 
through  which  the  positive  electricity  enters  the  electrolyte  is  called 
the  anode  {dvd^  above).  The  electrode  through  which  the  negative 
electricity  enters  the  electrolyte  is  called  the  cathode  (tcard^  below). 

Ions. — As  a  result  of  the  electrical  tension  ( =  difference  of  ten- 
sion, electrical  potential,  difference  of  potential,  electromotive  force) 
which  is  produced  by  the  electric  current  at  the  electrodes,  certain 
components  of  the  electrolyte,  the  ions  (loSv^  to  migrate),  move  with 
an  electric  charge  to  the  electrodes,  where  they  then  undergo  a  chemical 
alteration.  The  negative  electric  components  which  move  to  the 
anode  are  called  anions,  the  positive  electric  components  which  go 
to  the  cathode  are  called  cations. 

The  chemical  alteration  of  the  ions  at  the  electrodes  is  of  the 
following  character:  Either  the  elementary  ions  combine  with  one 
another  to  form  molecules,  or  the  elementary  ions  and  the  complex 
ions,  which  can  no  longer  exist  free  as  fractions  of  molecules,  enter 
into  chemical  reaction  with  the  water  which  serves  as  solvent,  with 
molecules  which  are  still  decomposed,  or  with  the  metal  of  the  elec- 
trodes. 

Such  so-called  secondary  processes  were  the  cause  of  the  erroneous 
idea  that  water  to  which  sulphuric  acid  had  been  added  was  decom- 
posed on  electrolysis,  because  in  this  case  hydrogen  is  evolved  at  the 
cathode  and  oxygen  at  the  anode.  Pure  water  does  not  conduct  the 
electric  current  at  all,  but  conducts  only  when  it  contains  salts,  bases, 
or  acids;  these  are  then  decomposed  and  their  ions  exert  a  decomposing 
action  on  the  water.  For  example,  sulphuric  acid,  HgSO^,  decomposes 
on  electrolysis  into  H„-f  SO4,  but  the  anion  S0^  cannot  exist  free  at  the 
anode  and  immediately  forms  sulphuric  acid  again  by  abstracting  from 
the  water  the  necessary  quantity  of  hydrogen:  S04  +  HOH=H2S04  +  0. 
Potassium  sulphate,  K2SO4,  dissolved  in  water  splits  up  on  electrolj'-sis 
into  the  cation  K,  which  immediately  decomposes  water  at  the  cathode, 
K2  +  2HOH-2KOH  +  H2,  and  into  the  anion  SO.,  which  likewise  de- 
composes water  at  the  anode  S04  +  HOH  =  H-,S04-f  O.  The  oxygen 
and  hydrogen  separated  from  water  on  electrolysis  therefore  originate 
only  indirectly  from  the  water. 

In  equal  periods  of  time  a  current  of  equal  strength  separates  the 
ions  from  solutions  of  electrolytes  in  quantities  by  weight  which  stand 


76  GENERAL  CHEMISTRY. 

in  the  same  ratio  to  one  another  as  their  equivalent  weights,  i.e.,  the 
atomic  weight  divided  by  their  valence  (Faraday's  law). 

It  should  be  noted  that  the  equivalent  weight  of  many  elements 
.'s  variable  according  to  the  valence  which  they  have  in  the  given  com- 
pound.    For  example,  in  cuprous  chloride  CuCl  copper  is  monovalent 

and  therefore  -^  parts  copper  and  -^  parts  chlorine  will  be  separated 

from  it;  from  cupric  chloride  CuCl.^,  however,  in  which  copper  is  divalent, 

—^  parts  copper  and  — ^  parts  chlorine  will  be  separated.     From  stan- 

1  1  o    r  nf\  o 

nous  chloride  SnClj  there  will  be  separated  — ^  parts  tin  and  — ^   parts 

chlorine,  from  stannic  chloride,  SnCl^,  — 2~  parts  tin  and  — -^   parts 
chlorine. 

The  strength  of  an  electric  current  can  therefore  be  measured 
by  determining  the  weight  of  copper  or  silver  separated  at  the  cathode 
in  a  given  time  from  a  solution  of  copper  or  silver,  or  by  measuring 
the  volume  of  hydrogen  and  oxygen  produced  from  water  (volt- 
ameter). 

Since  the  electric  current  can  be  cheaply  generated  with  dynamos, 
it  can  be  employed  for  many  purposes  in  chemistry. 

Among  the  practical  purposes  for  which  it  is  used  may  be  men- 
tioned the  following: 

1.  The  separation  of  pure  metals  from  their  ores  or  from  the 
raw  products  obtained  by  smelting  (Electrometallurgy). 

2.  The  preparation  of  detachable  metal  precipitates  on  the 
surface  of  conducting  objects,  or  of  objects  which  have  been  made 
conductors  (Galvano plastic),  and  the  coating  of  the  surface  of  common 
metals  with  noble  metals  (Electroplating). 

3.  The  preparation  of  valuable  chemicals  from  those  which 
are  less  valuable;  for  example,  the  preparation  of  soda,  chlorine, 
caustic  alkalies,  chloride  of  lime,  chlorates,  white  lead,  iodoform, 
percarbonates,  etc. 

4.  The  preparation  of  certain  chemical  substances  which,  as  soon 
as  produced,  can  be  employed  as  oxidizing  or  reducing  agents; 
viz.,  the  preparation  of  ozone. 

5.  The  determination  of  the  quantitative  composition  of  com- 
pounds (Electrochemical  analysis). 

6.  The  production   of  very  high  temperatures   (up    to    3000°) 


r 


ELECTROCHEMISTRY,  77 

in  order  to  carry  out  certain  chemical  reactions,  viz.,  the  reduction 
of  all  metal  oxides  by  carbon,  the  preparation  of  calcium  carbide  and 
other  carbides,  the  preparation  of  phosphorus,  etc. 

The  electric  furnace  consists  of  two  blocks  of  burnt  lime  (CaO)  fitting 
on  one  another.-  The  lower  block  contains  a  cavity  for  holding  the 
substance  to  be  heated  and  has  a  groove  on  the  edge  in  which  are  laid 
the  carbon  poles  for  producing  the  electric  arc.  The  furnace  is  closed 
by  the  upper  block  in  which  there  is  a  concave  depression  by  which  the 
heat  of  the  electric  arc  is  deflected  into  the  cavity  below,  so  that  a  de- 
composing action  from  the  electricity  itself  cannot  take  place. 

2.  Theory  of  the  Ions  or  of  Electrolytic  Dissociation. 

Neither  solid  electrolytes  (p.  74)  nor  pure  water  conduct  the 
electric  current  and  therefore  neither  of  them  are  decomposed  by  its 
action,  but  when  electrolytes  are  dissolved  in  water  the  solution 
becomes  a  conductor  of  electricity.  The  water  must  therefore  cause 
a  change  in  the  electrolytes  which  makes  it  possible  for  them  to 
conduct  the  electric  current,  and  in  fact  it  has  been  shown  that  the 
electric  current  is  not  the  cause  of  the  decomposition  of  the  electro- 
lytes, but  merely  causes  the  separation  of  the  ions  which  have  already 
been  formed  from  the  molecules  of  the  electrolytes  by  the  action 
of  the  water,  and  which  because  of  this  action  are  already  charged 
with  positive  and  negative  electricity  (Arrhenius'  theory  of  elec- 
trolytic dissociation). 

It  can  be  shown  by  the  fact  that  even  the  smallest  quantity  of 
electricity  causes  electrolysis;  no  expenditure  of  force  is  therefore 
necessary  for  splitting  up  the  electrolyte,  and  this  must  have  already 
taken  place  (however,  work  is  necessary  for  separation  at  the  elec- 
trodes) ;  moreover,  only  those  substances  are  electrolytes  which  show, 
in  aqueous  solutions,  an  osmotic  pressure  which  increases  with  the 
degree  of  dilution  and  a  correspondingly  greater  change  in  vapor 
pressure,  freezing-point,  and  boiling-point  than  corresponds  to  the 
molecular  weight  of  the  given  substance  (p.  20). 

The  positive  and  negative  ions  simultaneously  formed  must  bear 
equal  quantities  of  electricity,  since  it  is  a  fundamental  law  of  electricity 
that  onlv  equal  quantities  of  the  two  opposite  electricities  can  result 
from  an^  originally,  electrically  neutral  substance.  Therefore,  on  tfte 
electrolytic  dissociation  of  barium  chloride  (BaCl^),  for  example,  the 
barium  ion  contains  the  same  quantity  of  positive  ^^?^*""*y  ff'.  !V® 
negative  electricity  of  the  two  chlorine  ions  together.  ^^"^P^^,P^!^^';„,J 
electrified  ions  or"  cations  are  represented  by  hydrogen  and  the  metals 
complex  cations  by  ammonium  (NHJ  and  its  orgamc    denvatives,  as 


78  GENERAL  CHEMISTRY. 

well  as  by  the  analogous  compounds  of  phosphorus,  antimony,  and  arsenic; 
other  polyvalent  elements  can  also  form  complex  cations  with  carbon. 

Simple  liegatively  electrified  ions  or  anions  are  fornred  by  the  hydroxyl 
group  OH  ol'  the  bases  and  by  the  elements  of  the  chlorine  and  sulphur 
group,  complex  anions  are  formed  by  all  acids  minus  the  hydrogen  which 
is  replacable  by  metals  on  the  formation  of  salts  (p,  84). 

The  degree  of  dissociation  of  an  electrolyte  does  not  depend  only 
on  the  degree  of  dilution  of  its  solution,  but  also  on  its  temperature  and 
on  the  nature  of  the  electrolyta  Hydrochloric  acid  and  nitric  acid 
are  almost  completely  dissociated  in  solutions  which  contain  0.1  of  a 
gram-molecule  in  a  liter,  while  in  similar  solutions  carbonic  and  silicic 
acids  are  practically  not  dissociated  at  all;  of  the  bases  the  hydroxides 
of  the  alkalies  and  the  alkali  earths  are  almost  completely  dissociated 
at  this  dilution,  mercuric  chloride,  oiv  the  contrary,  but  very  little. 

If  it  is  assumed  that  the  electrolytes  (the  acids,  bases,  and  salts) 
undergo  a  splitting  up  into  their  ions  in  aqueous  solutions,  this  ex- 
plains also  the  increase  of  the  osmotic  pressure,  etc.,  on  the  dilution 
of  such  solutions,  since  by  the  formation  of  a  greater  number  of  con- 
stituents, namely  the  ions,  which  is  similar  in  effect  to  an  increase , 
in  the  number  of  the  molecules,  the  osmotic  pressure,  etc.,  is  in- 
creased. When  the  dilution  has  proceeded  to  a  certain  degree,  then 
further  dilution  causes  no  further  increase  in  the  osmotic  pressure, 
etc.,  since  all  the  molecules  have  then  been  split  up  into  their  ions. 
For  example,  the  molecule  NaCl,  when  completely  dissociated  into 
its  ions  Na+Cl,  acts  like  two  molecules;  the  molecule  Na2S04,  wljen 
completely  dissociated  into  its  ions  Na-1-Na+S04,  acts  like  three 
molecules  of  a  non-electrolyte  with  respect  to  the  osmotic  pressure, 
etc. 

An  analogous  phenomenon  is  exhibited  on  the  dissociation  of  gases 
(p.  72)  by  heat,  which  is  the  cause  of  the  fact  that  the  dissociable  gases 
at  a  given  volume  and  a  given  temperature  exert,  a  pressure  which  is 
greater  than  that  corresponding  to  the  molecular  weight  of  the  given 
gas.  The  number  of  the  molecules  and  therefore  the  pressure  of  the 
gas  is  increased  by  the  dissociation. 

The  aqueous  solutions  of  the  electrolytes  show  exactly  the  same 
behavior  with  respect  to  the  electric  current,  since  with  increasing 
dilution  their  conductivity  with  respect  to  the  quantity  of  dissolved 
substance  constantly  increases  until  finally  a  limiting  value  is  attained. 

From  the  knowledge  of  this  limiting  value,  the  degree  of  dissociation 
of  an  electrolyte  in  more  concentrated  solution  can  be  calculated;  and 
further,  from  the  increase  of  the  conductivity  of  chemically  pure  water 
on  shaking  with  apparently  insoluble  electrolytes  it  can  be  determined 
whether  these  are  soluble  in  water.     Many  electrolytes  when  fused  con- 


ELECTROCHEMISTRY.  79 

duct  themselves  with  respect  to  the  electric  current  as  they  do  in  aqueous 
solutions,  and  therefore,  on  fusion,  a  more  or  less  general  splitting  up 
of  the  molecules  into  ions  must  take  place. 

The  dissociation  of  the  electrolytes  into  their  ions  in  aqueous 
solutions  is  called  electrolytic  dissociation  and  differs  therein  from 
thermal  dissociation  in  that  the  compounds  do  not  split  up  into 
simpler  molecules  which  can  exist  free,  but  into  atoms  or  atomic 
complexes  called  ions,  which  cannot  be  isolated,  but  can  only  exist 
in  solution.  Half  of  the  ions,  the  cations,  are  electropositive;  the 
other  half,  the  anions,  are  electronegative. 

The  power  possessed  by  water  to  split  up  a  substance  into  its 
ions  is  called  dissociating  force;  besides  water  certain  other  liquids 
also  have  this  force,  but  none  so  strongly  as  water.  Formic  acid 
has  about  six-eighths,  methyl  alcohol  three-eighths,  acetone  and 
alcohol  about  two-eighths  of  the  dissociating  force  of  water.  The 
solutions  of  electrolytes  in  liquids  which  have  no  dissociating  force 
cannot  conduct  the  electric  current  and  show  an  osmotic  pressure 
corresponding  to  the  normal  molecular  weight  of  the  given  electro- 
lyte, for  which  reason  such  solvents  must  be  used  instead  of  water 
in  determining  the  molecular  weights  by  the  osmotic  pressure. 

For  example,  if  sal  ammoniac  NH4CI  is  dissolved  in  much  water,  it 
dissociates  into  the  positive  ion  NH4  and  the  negative  ion  CI;  if,  however, 
it  is  brought  into  the  gaseous  form  by  warming,  it  dissociates  into  the 
unelectrified  molecules  NH3  +  HCI,  which  can  be  at  least  partially  sepa- 
rated by  diffusion.  The  products  of  thermal  dissociation  can  be  mixed 
in  all  proportions,  and  the  separation  of  the  products  involves  no  other 
work  than  the  components  of  a  gaseous  mixture.  In  the  case  of  the 
products  of  electrolytic  dissociation,  on  the  contrary,  there  are  always 
just  as  many  positive  as  negative  ions  present  as  would  be  necessary  for 
their  mutual  electrical  neutralization,  and  for  separating  the  ions  from 
one  another  there  is  required  in  addition  to  the  work  of  moving  them 
to  the  electrodes  also  the  work  of  overcoming  the  force  of  attraction 
which  the  oppositelv  charged  ions  exert  on  one  another  and  which  can 
be  brought  about  only  wHth  the  help  of  the  electric  current.  The  separa- 
tion can  therefore  not  be  carried  out  by  diffusion,  as  with  thermic  dis- 
sociation, but  can  be  effected  only  by  electrolysis. 

The  assumption  that  the  ions  formed  from  the  electrolytes  are 
charged  partly  positively  and  partly  negatively,  although  no  free 
electricity  can  be  detected  in  the  solutions  of  the  electrolytes,  since 
on  dissolving  the  electrolytes  an  equal  number  of  oppositely  charged 
ions  are  simultaneously  formed  and  therefore  the  given  solution 
can  show  no  electric  charge,  is  explained  as  follows:   The  separation 


80  GENERAL  CHEMISTRY. 

of  the  ions  at  the  electrodes  shows  that  the  conduction  of  the  electric 
current  in  dissolved  electrolytes,  in  contrast  to  the  conduction  in 
metals,  is  associated  with  a  transportation  of  matter,  and  in  fact  the 
cations  move  to  the  negatively  charged  cathode,  the  anions  to  the 
positively  charged  anode,  in  order  there  to  separate  out.  This  can  be 
best  explained  by  assuming  that  the  cations,  because  of  their  positive 
electric  charge,  and  the  anions,  because  of  their  negative  electric 
charge,  are  attracted  by  the  oppositely  charged  electrodes. 

The  fact  that  many  substances  which,  in  the  form  of  atoms  and 
molecules,  enter  into  chemical  reaction  with  water  can  exist  in  it  in 
the  form  of  ions  can  likewise  be  explained  by  the  assumption  of 
electrically  charged  ions.  For  example,  the  potassium  atoms  react 
with  water  as  follows:  K+HOH  =  KOH-f  H;  the  electropositively 
charged  potassium  ions,  on  the  contrary,  act  indifferently  towards 
water  until  on  giving  up  their  positive  electricity  at  the  cathode 
they  pass  over  into  unelectrified  potassium  atoms,  for  which  reason 
the  potassium  appearing  at  the  cathode  (for  example,  in  the  elec- 
trolysis of  KCl)  immediately  reacts  with  water.  This  assumption  is 
further  substantiated  by  the  fact  that  zinc  when  charged  with  posi- 
tive electricity  does  not  dissolve  in  dilute  hydrochloric  acid,  while 
the  ordinary,  non-electrified  zinc  does  dissolve. 

The  electronegatively  charged  chlorine  ion  is  entirely  different 
from  the  free,  unelectrified,  gaseous  chlorine  molecule;  the  former  in 
contrast  to  the  latter  has  neither  color,  odor,  nor  bleaching  properties; 
like  all  other  ions  it  cannot  exist  as  a  gas,  but  can  exist  only  in  solu- 
tion. 

The  property  of  many  elements  to  appear  in  forms  (allotropic 
modifications)  which  exhibit  an  entirely  different  chemical  and  physi- 
cal behavior  is  called  allotropism  {dXXorpoTto^^  in  another  way). 

In  addition  to  the  simpler  or  elementary  ions  there  are  also  com- 
plex ions  which  have  the  same  composition  as  other  substances  which 
are  not  ions,  but  which  have  entirely  different  properties  from  the 
latter;  for  example,  the  hydroxyl  ion  OH'  and  the  hydrogen  peroxide 
molecule  O2H2,  the  cyanogen  ion  CN'  and  the  dicyanogen  molecule  CjNj. 

The  property  of  many  compounds  of  exactly  similar  qualitative 
and  quantitative  composition  to  appear  in  forms  which  show  entirely 
different  chemical  and  physical  behavior  is  called  isomerism  (p.  30). 

Allotropism  and  isomerism  can  not  only  be  caused  by  electrification 


ELECTROCHEMISTRY.  81 

and  non-electrification,  but  allotropism  exists  also  when  (as  in  the  case 
of  ozone  sulphur,  phosphorus,  and  carbon,  which  see)  the  different 
modifications  of  the  given  element  contain  a  different  number  of  atoms 
in  the  molecule.  Isomerism,  as  is  known  in  the  case  of  the  carbon  com- 
pounds (which  see),  also  occurs  when  the  atoms  which  form  the  mole- 
cules of  a  compound  have  a  different  arrangement  (p.  30)  or  when  the 
molecular  weights  are  whole  multiples  of  one  another. 

Ions  which  do  not  act  on  water  can  combine  to  form  free  mole- 
cules at  the  electrodes,  since  after  giving  up  their  electric  charges 
they  no  longer  repel  each  other,  and  likewise  metal  ions  whose 
(molecules  consist  of  one  atom)  can  form  unelectrified,  monatomic, 
free  molecules.  For  example,  two  negative  chlorine  atoms  will 
combine  to  form  one  chlorine  molecule,  two  negative  hydroxyl  ions 
will  combine  to  form  one  HjOj  molecule,  one  positive  copper  ion  will 
pass  over  into  a  copper  molecule,  etc. 

The  fact  that  the  electrically  oppositely  charged  ions  do  not 
neutralize  their  electricities  in  solution  can  be  explained  by  the 
assumption  that  their  number  is  very  small  as  compared  to  the 
water  molecules  which  lie  between  them,  so  that  the  latter  acts 
as  an  insulator,  and  this  action  is  greater  the  more  the  quantity  of 
water  (or  the  quantity  of  other  dissociating  liquid)  exceeds  that 
of  the  electrolyte.  Therefore  in  concentrated  solutions  the  possi- 
bility that  the  electrified  ions  will  combine  to  form  non-conducting, 
and  therefore  non-dissociated,  compounds  is  much  greater,  since 
in  this  case  they  are  not  so  widely  separated  from  one  another. 

The  transportation  of  the  electricity  supplied  to  the  solution 
by  the  electrodes  is  carried  out  by  the  movement  of  the  electrically 
charged  ions  to  the  electrodes.  Since,  for  example,  the  positive 
ions  are  attracted  by  the  negatively  charged  electrode  and  therefore 
move  towards  this  and  give  up  their  electricity  to  it,  they  can  no 
longer  exist  as  ions,  but  separate  at  the  electrode  as  atoms  or  groups 
of  atoms.  The  negative  ions  undergo  a  similar  change  at  the  posi- 
tively charged  electrode.  As  a  result  of  this  giving  up  of  electricity 
at  the  electrodes  the  solution  receives  at  each  of  these  points  an 
excess  of  electricity  with  which  the  electrodes  are  charged,  and  this 
electricity  moves  with  the  repelled  ions  (namely,  the  ions  which  carry 
electricity  similar  to  that  of  the  repelling  electrodes)  through  the 
liquid  to  the  other  electrode. 

Since  it  is  exclusively  the  free  ions  which  conduct  the  electricity, 
therefore  with  an  increase  in  the  ions,  such  as  is  produced  by  the  in- 


82  GENERAL  CHEMISTRY. 

creased  dissociation  caused  by  dilution,  the  conductivity  of  the  solu- 
tion will  increase  with  respect  to  the  quantity  of  dissolved  substance. 
The  quantity  of  electricity  which  the  ions  transport  through  the 
solution,  in  the  manner  that  a  ship  carries  its  cargo,  is  an  unalterable 
quantity  and,  for  each  gram-equivalent  of  any  ion,  is  equal  to  96537 
coulombs.  From  this  will  be  understood  the  law  of  Faraday,  that 
equal  quantities  of  current  separate  equivalent  quantities  of  different 
substances  (p.  75). 

Ions  which  are  charged  with  quantities  of  electricity  equal  to  that  of  the 
hydrogen  ion  or  the  chlorine  ion  are  called  monovalent  ions,  those  charged 
with  the  double  quantity  of  electricity  are  called  divalent  ions,  etc. 

Compounds  of  monovalent  ions  when  completely  dissociated  have 
an  osmotic  pressure  which  is  twice  as  great  as  that  which  they  would 
have  if  undissociated,  since  on  dissociation  they  split  up  into  two  ions 
(for  example,  KCl  into  K  +  Cl);  compounds  of  divalent  ions  have  an 
osmotic  pressure  three  times  as  great,  since  they  split  up  into  three  ions 
(for  example,  BaCl2=Ba  +  Cl  +  Cl),  etc. 

Electropositive  ions  are  denoted,  according  to  their  valence,  by  dots 

E laced  after  their  chemical  symbols  or  formulas,  electronegative  ions 
y  accents.  For  example,  K*,  Ba",  CV,  SO/'. 
As  already  mentioned  (p.  77),  the  movement  of  the  electrolyte  in 
the  solution  takes  place  without  loss  of  energy,  since  an  apparently  insig- 
nificant part  of  the  electricity  serves  to  move  the  ions  to  the  electrodes 
(to  overcome  the  friction  of  the  ions  on  the  molecules  of  the  liquid)  and 
appears  again  as  heat  (heat-work  of  the  electric  current) ;  on  the  contrary, 
another  part  of  the  electricity  is  used  up  in  neutralizing  the  ions  which  have 
moved  to  the  electrodes  and  to  separate  them  as  molecules,  etc.  (chemical 
work  of  the  electric  current) ;  this  part  is  equal  to  96537  coulombs. 

The  ions  move  to  the  two  electrodes  with  different  velocities 
and  the  quantity  of  electricity  carried  in  the  unit  time  depends  not 
only  on  the  number  of  the  transporting  ions,  but  also  on  their  velocities. 

Since  equivalent  quantities  of  ions  are  always  separated  at  the  elec- 
trodes (p.  77)  it  might  be  supposed  that  the  velocities  of  the  ions  toward 
the  two  electrodes  were  the  same;  the  contrary,  however,  can  be  shown 
to  be  the  fact,  since  if  the  electric  current  is  passed  through  the  solution 
for  some  time  the  solution  at  one  electrode  becomes  more  concentrated, 
the  solution  at  the  other  electrode  becomes  more  dilute. 

The  ions  of  different  substances  have  a  different  electroaffinity 
or  intensity  of  attachment,  namely  they  possess  a  different  power  to 
retain  their  electric  charge  and  they  are  therefore  distinguished  as 
strong  and  weak  ions;  the  former  form  mostly  easily  soluble  and 
readily  dissociating  compounds,  the  latter  mostly  difficultly  soluble 
and  difficultly  dissociating  compounds. 


ELECTROCHEMISTRY.  83 

When  a  substance  of  strong  electroafFiriity  which  is  not  in  the  ion 
state  comes  into  contact  with  ions  which  have  a  lower  electroaffinity, 
the  former  seizes  the  ionic  charge  of  the  latter  and  passes  into  the  form 
of  ions,  while  the  substance  with  weaker  electroaffinity  is  converted 
into  electrically  neutral  ions  Catoms).  For  example,  on  dipping  metallic 
zinc  into  a  solution  of  a  lead  salt  the  zinc  passes  over  into  zinc  ions  and 
metallic  lead  is  separated,  metallic  lead  separates  copper  ions  as  metallic 
copper,  and  metallic  copper  separates  mercury  ions  as  metallic  mercury 
(p.  88). 

The  ion  theory  not  only  forms  the  basis  of  electrochemistry, 
but  it  has  furnished  an  explanation  of  many  other  phenomena  in 
physics  and  chemistry  which  were  formerly  not  understood.  With 
its  assistance  many  important  discoveries  in  these  subjects  have 
been  made  possible. 

The  readiness  with  which  electrolytes  enter  into  reactions  and  the 
velocity  with  which  their  chemical  action  proceeds,  in  contrast  to  the 
slowness  with  which  non-electrolytes,  namely  the  carbon  compounds, 
enter  into  reaction,  was  first  explained  by  the  ion  theory.  The  more 
completely  an  electrolyte  is  dissociated  the  greater  is  its  conductivity 
and  its  chemical  activity,  since  it  is  the  free  ions  only  which  react. 
For  example,  hydrogen  chloride  when  dissolved  in  chloroform  does 
not  act  on  carbonates,  since  in  this  case  no  dissociation  of  HCl  is 
possible;  on  the  qiddition  of  water  the  action  takes  place  immedi- 
ately and  the  carbonates  are  decomposed  with  the  evolution  of  carbon 
dioxide. 

The  chemical  properties  of  aqueous  solutions  of  electrolytes 
depend  on  the  properties  of  the  free  ions  which  they  contain;  for 
example,  in  all  solutions  of  silver  salts  the  silver  ion  Ag'  can  be  de- 
tected by  one  and  the  same  reagent,  namely  by  compounds  which 
contain  the  chlorine  ion  CI';  likewise  in  all  soluble  compounds  of 
chlorine  with  hydrogen  and  metals  the  chlorine  ion  CI'  can  be  de- 
tected by  all  compounds  which  contain  the  silver  ion  Ag" ;  all  dissolved 
compounds  which  contain  the  ion  SO4"  can  be  detected  by  com- 
pounds which  contain  the  ion  Ba"  and  vice  versa. 

On  the  other  hand,  however,  the  chlorine  ion  CI'  does  not  produce 
a  precipitate  in  the  aqueous  solutions  of  silver  salts  with  potassium 
cyanide,  KCN,  since  such  solutions  contain  the  components  of  the 
salt  KAg(CN)2,  namely  the  ions  K'  and  Ag(CN)/,  and  the  latter 
ion  shows  different  reactions  from  the  Ag*  ion. 

The  aqueous  solutions  of  the  copper  salts  have  a  blue  color  which  is 
due  to  the  Cu"  ion :  the  solutions  of  the  salt  KjCu^CN^  on  the  contrary  are 


84  GENERAL  CHEMISTRY, 

colorless,  since  they  contain  the  complex  ion  CUC4N4';  CuCla  in  concen- 
trated aqueous  of  alcoholic  solutions  is  only  slightly  dissociated  and 
therefore  tliese  solutions  have  the  greenish-yellow  color  of  the  CuClj 
molecule;  on  diluting  the  solution,  because  of  the  increased  dissociation, 
the  blue  color  of  the  Cu"  ions  appears. 

Those  ions  which  contain  constituents  that  as  such  are  not  ions, 
but  which,  on  the  other  hand,  can  exist  themselves  as  ions,  are  called 
complexes. 

In  the  solutions  of  the  chlorine  containing  compounds  chloric  acid, 
HCIO3,  and  trichloracetic  acid,  HC^jCip^,  and  in  their  salts,  the  silver  ion 
Ag-  does  not  produce  a  precipitate,  since  here  the  chlorine  is  not  present 
as  the  Cr  ion,  but  is  combined  with  other  elements  as  the  complex  ions 
CIO/  and  C2CI3O2,  respectively. 

The  iron  ion  Fe/-  is  precipitated  from  its  solutions  by  hydrogen  sul- 
phide, but  is  not  precipitated  by  this  reagent  from  the  solutions  of  potas- 
sium ferrocyanide,  K/FeCgNe,  since  on  dissolving  this  salt  the  complex 
ion  FeCgNg'  and  not  the  ion  Fe*-  is  formed. 

The  ion  theory  is  also  of  importance  for  physiological  chemistry. 
For  example,  the  poisonous  action  of  certain  metallic  salts  is  propor- 
tional to  their  dissociation  and  therefore  alcoholic  solutions  of  mer- 
curic chloride  or  silver  nitrate,  which  are  less  dissociated  than  their 
aqueous  solutions,  are  not  fatal  to  anthrax  bacilli.  The  salts  of 
many  metals  which  are  poisonous,  as  cations,  for  example,  Cu",  Ag', 
Hg"',  lose  their  poisonous  properties  when  they  form  complex  anions 
(even  with  the  poisonous  cyanogen  CN').  For  example,  the  silver 
ion  Ag'  of  the  salt  AgN03  has  a  stronger  disinfectant  action  than 
the  complex  ion  Ag(CN)/  of  potassium  silver  cyanide,  KAg(CN)2, 
the  anion  CN'  is  a  powerful  poison,  the  anion  FeCgN/  of  potassium 
ferrocyanide  is  not  poisonous. 

The  group  of  electrolytes  comprising  acids,  bases,  and  salts  (p.  74) 
are  defined  by  the  ion  theory  as  follows : 

Acids  are  hydrogen  compounds  which  on  electrolytic  dissocia- 
tion split  up  partially  or  entirely  into  cations  of  hydrogen  and  anions 
of  non-metals  or  anions  consisting  of  atomic  groups;  the  hydrogen 
cations  produce  their  acid  taste  and  acid  reaction,  namely,  their 
property  of  turning  litmus  red  when  it  has  been  colored  blue  by 
bases  and  of  decolorizing  phenolphthalein  solution  which  has  been 
colored  red  by  bases  (see  Indicators,  p.  87). 

Bases  are  hydro xyl  compounds  which  on  electrolytic  dissocia- 
tion split  up  partially  or  entirely  into  hydroxyl  ions  (OH')  and  metal 
ions;    the  hydroxyl  ions  cause  the  alkaline  taste  and  the  alkaline 


.       ELECTROCHEMISTRY,  85 

(basic)  reaction,  namely,  the  property  of  turning  red  litmus  blue, 
of  turning  yellow  tumeric  brown,  and  of  coloring  colorless  phenol- 
phthalein  red  (see  Indicators,  p.  87). 

The  strength  of  acids  (avidity)  and  likewise  of  bases  is  determined 
by  the  number  of  H*  ions  and  OH'  ions  respectively  present  in  their 
solutions,  also  by  their  degree  of  dissociation.  In  completely  anhydrous 
and  therefore  non -dissociated  condition  the  acids  do  not  exhibit  either 
acid  reactions  or  the  ability  to  form  salts  (see  below).  The  strongest 
acids  are  hydrochloric,  hydrobromic,  hydriodic,  nitric,  chloric,  and  sul- 
phuric; the  strongest  bases  are  the  hydroxyl  compounds  (hydroxides)  of 
the  alkali  and  alkaline-earth  metals. 

Salts  are  metal  compounds  which  on  electrolytic  dissociation 
partially  or  entirely  split  up  into  metal  cations  (the  acid  salts  also 
into  hydrogen  cations)  and  into  acid  anions;  salts  dissociate  more 
readily  and  more  completely  than  acids  and  bases  and  the  salts  of 
the  monovalent  metal  cations  are  the  most  strongly  dissociated. 
The  formation  of  salts  results  from  the  substitution  of  the  hydrogen 
cation  of  acids  by  metal  cations,  after  which  the  displaced  hydrogen 
cation  either  escapes  in  a  non-electric  form  as  gas  or  combines  with 
the  hydroxyl  ion  of  the  base  to  form  only  very  slightly  dissociated 
water. 

If  all  of  the  hydrogen  cations  of  the  acid  are  replaced  by  metal 
cations,  then  a  neutral  (neutral  reacting)  salt  is  formed,  namely,  a 
salt  which  tastes  neither  acid  nor  alkaline,  but  simply  salty,  and 
which  does  not  alter  either  litmus,  tumeric,  or  phenolphthalein. 
If  the  hydrogen  cations  of  a  polybasic  (i.e.,  having  more  than  one 
hydrogen  cation)  acid  are  only  partially  replaced  by  metal  cations 
then  an  add  salt  is  formed  which  still  gives  hydrogen  cations  on  disso- 
ciation and  which  therefore  shows  an  acid  reaction  in  aqueous  solutions. 

The  formation  of  salts,  which  takes  place  by  the  action  of  acids 
on  bases  in  aqueous  solutions,  consists  merely  in  a  combination  of  the 
H'  ions  of  the  acid  with  the  OH'  ions  of  the  base  to  form  water,  since 
the  latter  is  only  very  slightly  dissociated  (see  below),  while  the 
metal  cations  and  the  acid  anions  remain  to  a  greater  or  less  extent 
uncombined  in  the  solution.  After  the  evaporation  of  the  solvent 
which  causes  the  dissociation  these  ions  combine  to  form  a  salt. 

That  this  phenomenon  of  salt  formation  depends  only  on  the  com- 
bination of  the  H-  ions  with  the  OH'  ions  is  shown  by  the  fact  that 
on  the  neutralization  of  equimolecular  quantities  of  acids  (i.e.,  quantities 
of  acids  which  are  neutrahzed  by  the  same  quantity  of  a  given  base. 


S6  GENERAL  CHEMISTRY,    . 

viz.,  — Y— ,  —hr^t  —\ — *>  6tc.)  in  very  dilute  solutions  (when  the  dis- 

sociation  of  the  given  substance  is  complete)  with  bases  the  heat  of 
neutralization  is  the  same  for  the  different  acids.  If,  however,  in  the  fore- 
going process  a  salt  was  actually  formed  in  the  solution,  then  the  heat  of 
neutralization  would  correspond  to  the  heat  of  formation  of  the  given 
salt  (which  has  a  different  value  for  different  salts).  Moreover,  when 
dilute  solutions  of  different  neutral  salts  are  mixed  (when  they  do  not 
precipitate  one  another),  there  is  no  thermal  effect  produced  (law  of 
thermal  neutrality),  which  shows  that  the  ions  of  the  different  salts 
remain  side  by  side  unconibined  in  the  solution,  namely  that  on  mixing 
no  change  in  condition  takes  place.  A  dilute  solution  of  NaCl  +  KNOj  or 
of  NaNOg  +  KCl  are  therefore  identical  and  both  contain  the  ions  Na'  + 
NO^  +  K'  +  Cl'. 

Neutral  salts  of  weak  acids  can  show  alkaline  reactions  in  aqueous 
solutions,  salts  of  weak  bases  can  show  acid  reactions.  This  is  a 
result  of  the  hydrolytic  dissociation,  i.e.,  dissociation  under  the 
action  of  the  ions  of  water,  as  a  result  of  which  the  salts  of  weak 
acids  on  the  one  hand  split  up  into  non-dissociating  (not  acid-react- 
ing) acids  and  dissociated  bases,  on  the  other  hand  the  salts  of  the 
weaker  bases  split  up  into  undissociated  (not  alkaline-reacting) 
bases  and  dissociated  acids. 

The  electrical  conductivity  of  absolutely  pure  water,  which  is  ex- 
tremely slight  but  still  measurable,  shows  that  even  water  is  slightly 
dissociated  into  its  ions  H*  and  OH'  (p.  78).  These  ions  will  now  com- 
bine with  the  cations  and  anions  produced  on  dissolving  the  given  salt 
in  water  to  form  undissociated  acids  or  bases,  since  the  slightly  dissociating 
acids  and  bases  require  no  more  H*  or  OH'  ions  to  prevent  their  dissocia- 
tion than  are  present  in  the  water.  Small  quantities  of  these  ions  are 
sufficient  to  cause  a  partial  re-formation  of  acid  or  base,  while  on  the 
other  hand  the  stronger  acids  and  bases  remain  dissociated  and  a  corre- 
sponding acid  or  basic  reaction  must  appear. 

For  example,  potassium  cyanide,  KCN,  a  salt  of  the  weak  hydro- 
cyanic acid  HON  and  the  strong  base  KOH,  when  dissolved  in  water 
exhibits  the  alkaline  reaction  of  the  OH'  ions  and  the  characteristic  odor 
of  undissociated  hydrocyanic  acid,  although  the  K*  ions  formed  on  elec- 
trolytic dissociation  do  not  react  alkaline  and  the  CN'  ions  are  not  volatile. 
The  alkaline  reaction  is  explained  bv  the  fact  that  the  alkaline  reacting 
OH'  ions  of  the  water  are  present  as  well  as  the  K"  ions,  but  that  these 
cannot  combine  with  one  another  because  KOH  being  a  strong  electro- 
lyte is  strongly  dissociated,  while  the  H*  ions  of  the  water  are  used 
lip  by  combining  with  the  CN'  ions  to  form  hydrocyanic  acid,  which  is  a 
weak  and  th*>refore  but  slightly  dissociated  acid. 

Fernc  chloride,  FeCl,,  the  yellow  salt  of  the  weak  base  Fe(OH), 
and  the  strong  acid  HCl,  on  dissolving  in  water  shows  a  strongly  acid 
reaction  and  the  solution  becomes  reddish  brown,  although  the  Fe- 
lon, formed  by  electrolytic  dissociation,  is  yellow  and  the  CI'  ions  do 
not  react  acid.     The  acid  reaction  of  the  solution  is  explained  by  the 


ELECTROCHEMISTRY,  87 

fact  that  acid -reacting  H-  ions  of  the  water  are  present  in  the  solution 
as  well  as  CI'  ions,  and  these  cannot  combine  with  one  another  because 
HCl  is  a  strong  electrolyte,  while  the  OH'  ions  of  the  water  are  used  up 
in  forming  the  brown  base  Fe(0H)3  with  the  Fe*-'  ions,  this  base  being 
weak  and  therefore  scarcely  dissociated. 

Since  the  dissociation  of  water  increases  with  the  temperature,  on 
warming  the  hydrolytic  dissociation  increases  also. 

Hydrolytic  dissociation  is  also  called  hydrolysis,  but  this  must 
not  be  confused  with  the  term  applied  to  the  splitting  up  of  the 
molecules  of  complicated,  non-electrolytic,  organic  compounds  into 
simpler  molecules  with  the  simultaneous  addition  of  the  elements 
of  water,  which  is  also  called  hydrolysis. 

The  natural  or  artificial  dyes  which  undergo  a  change  in  color  by 
the  action  of  dissolved  acids  or  bases,  and  which  therefore  serve  for  the 
identification  of  these  substances  as  well  as  for  demonstrating  neutraliza- 
tion (p.  84),  are  called  indicators.  These  indicators  are  weak  acids 
or  bases  which  have  a  different  color  when  they  are  dissociated  from  that 
which  they  have  when  undissociated.  Since  only  weak  acids  or  bases 
on  solution  do  not  split  up  into  ions,  while  their  neutral  salts  are  very 
completely  dissociated,  therefore  on  the  addition  of  the  slightest  quan- 
tity of  an  acid  or  base  the  formation  of  a  dissociating  salt  immediately 
occurs  and  the  color  of  the  indicator  immediately  undergoes  an  altera- 
tion. Undissociated  litmus  is  a  weak,  red  acid  which  is  colored  blue  by 
a  trace  of  alkali  (base),  since  the  resulting  salt  immediately  dissociates 
into  metal  cations  of  the  base  and  the  blue  anions  of  litmus  acid.  If 
an  acid  which  dissociates  more  readily  than  litmus  be  added,  then  the 
H*  ions  of  the  former  convert  the  blue  litmus  anions  into  undissociated, 
red  litmus.  Undissociated  phenolphthalein  is  a  weak,  colorless  acid 
which  is  colored  red  by  traces  of  bases,  because  the  resulting  salt  im- 
mediately dissociates  into  metal  cations  and  red  anions  of  phenolphthalein. 
The  H.  ions  of  a  more  readily  dissociating  acid  convert  the  latter  into 
undissociated  colorless  phenolphthalein  again. 

3.  Transformation  of  Chemical  Energy  into  Electrical  Energy. 

The  simplest  and  best  known  chemical  systems  in  which  the 
energy  associated  with  chemical  phenomena  is  converted  into  elec- 
trical energy  are  the  galvanic  elements  or  voltaic  cells.  These  are 
combinations  of  conductors  of  the  first  order  (metals  or  carbon) 
with  conductors  of  the  second  order  (electrolytes)  from  which  an 
electric  current  is  obtained. 

Since  it  is  only  in  electrolytes  that  the  conduction  of  the  current 
is  associated  with  chemical  reaction,  therefore  all  galvanic  elements 
must  contain  electrolytes  which  up  to  the  present  have  been  em- 
ployed almost  exclusively  dissolved  in  water  or  fused. 


88  GENERAL  CHEMISTRY, 

It  is  a  characteristic  of  all  galvanic  cells  that  the  substances  which 
enter  into  chemical  reaction  must  be  separated  from  one  another  and 
that  a  conductmg  connection  is  necessary  in  order  that  the  reaction 
can  take  place,  while  without  this  connection  galvanic  cells  can  be  kept 
for  a  long  time  without  any  chemical  reaction  resulting.  From  this, 
however,  it  cannot  be  assumed  that  m  a  galvanic  couple  the  chemical 
Bystem  is  in  a  state  of  equilibrium,  any  more  than  this  can  be  assumed 
in  the  case  of  a  mixture  of  hydrogen  and  oxygen,  which  apparently  does 
not  change  on  standing.  The  fact  is  that  m  both  cases  the  velocity  of 
reaction  is  extremely  smnll  (p.  66). 

Just  as  in  the  transformation  of  electrical  energy  into  chemical 
energy  a  portion  of  the  former  passes  over  into  heat,  so  also  in  the 
transformation  of  chemical  energy  into  electrical  energy  thermal 
changes  occur.  Those  cells  whose  electromotive  force  decreases  with 
the  temperature  convert  a  portion  of  their  chemical  energy  into 
heat;  on  the  other  hand,  those  cells  whose  electromotive  force  in- 
creases with  the  temperature  produce  more  electrical  energy  than 
corresponds  to  the  chemical  energy  which  they  consume.  They 
supply  the  deficit  by  the  absorption  of  heat  from  their  surroundings 
and  therefore  become  cooler  when  they  are  working. 

Just  as  a  salt  dissolves  in  a  Hquid  until  the  osmotic  pressure  of 
its  solution  is  in  equilibrium  with  the  particular  solution  tension 
(p.  51)  of  the  salt,  so  every  metal  has  a  force,  dependent  on  its  chemical 
nature,  sufficient  to  send  positively  electrically  charged  ions  (cations) 
into  solution.  This  force  is  called  the  electrolytic  solution  tension 
(solution  or  ionizing  pressure)  and  becomes  active  when  the  metal 
is  dipped  into  the  aqueous  solution  of  one  of  its  salts.  It  is  the 
more  active  the  less  cations  of  the  metal  there  are  already  in  the 
solution,  namely,  the  smaller  the  osmotic  pressure  of  the  cations 
already  in  solution  (Nemst's  theory  of  galvanic  cells). 

The  electromotive  force  obtained  in  chemical  processes  therefore 
depends  on  the  solution  tension  of  the  metals,  and  as  shown  in  the 
following  arrangement,  in  which  hydrogen,  which  behaves  like  a 
metal,  is  included,  decreases  from  potassium  on:  K,  Na,  Mg,  Al, 
Mn,  Zn,  Cd,  Fe,  Co,  Ni,  Sn,  Pb,  H,  Sb,  Bi,  As,  Cu,  Hg,  Ag,  Pd,  Pt, 
Au  (electromotive  series). 

The  solution  tension  of  magnesium  and  zinc,  for  example,  is  equal 
to  several  millions  of  atmospheres;  of  copper,  mercury,  and  silver  it  is 
only  about  one- trillion th  of  an  atmosphere;  it  is  therefore  impossible 
to  prepare  a  solution  of  a  zinc  salt  which  is  sufficiently  concentrated 
to  prevent  the  sending  out  of  positive  zinc  ions  into  the  solution,  while  in 
the  case  of  copper  and  the  following  metals  the  osmotic  pressure  of  the 


ELECTROCHEMISTRY.  89 

metal  ions  is  greater  in  even  extremely  dilute  solutions  than  the  solution 
pressure  of  the  metal.  Therefore  when  metallic  zinc  is  immersed  in 
the  solution  of  a  zinc  salt  it  becomes  negatively  electrified  by  sending 
out  positive  zinc  ions  into  the  solution,  while  copper  immersed  in  a  solu- 
tion of  a  copper  salt  becomes  positively  electrified  because  the  positive 
copper  ions  pass  out  of  the  solution  to  the  copper  and  leave  the  solution 
negatively  electrified. 

The  arrangement  of  the  metals  according  to  their  decreasing 
solution  tension  corresponds  to  the  arrangement  according  to  their 
decreasing  electroaffinity,  so  that  every  metal  precipitates  those 
standing  to  the  right  of  it  from  their  solutions.  The  tendency  of 
the  metals  to  oxidize  also  decreases  from  left  to  right. 

The  farther  apart  two  metals  stand  in  the  row,  the  greater  is  the 
electromotive  force  or  electric  tension  of  a  galvanic  element  formed 
by  combining  them.  For  this  reason  this  arrangement  is  also  called 
the  electromotive  series. 

A  knowledge  of  the  electromotive  series  is  of  practical  importance, 
since  in  all  cases  where  objects  of  metal  (alloys,  combinations  of  metals 
in  contact,  metals  with  mechanically  or  galvanically  prepared  metallic 
coatings)  are  exposed  to  the  action  of  the  elements  an  opportunity  is 
afforded  for  the  formation  of  short-circuited  galvanic  couples,  as  a  result 
of  which  the  metal  with  the  highest  solution  tension  dissolves,  but  the 
other  remains  intact.  Galvanized  iron  is  therefore  not  so  strongly  oxi- 
dized at  points  where  the  zinc  covering  has  been  injured  as  if  it  were  not 
galvanized,  while  tinned  iron  on  an  injury  to  the  tin  coating  oxidizes 
(rusts)  more  readily  than  it  would  if  it  were  not  tinned,  because  iron 
has  a  greater  solution  tension  than  tin  and  a  lower  solution  tension  than 
zinc. 

Concentration  cells  are  formed  when  two  rods  of  the  same  metal 
are  brought  as  electrodes  into  two  solutions  of  a  salt  of  the  metal, 
the  solutions  being  of  different  concentration  but  in  contact  with 
one  another;  for  example,  two  silver  rods  in  two  solutions  of  silver 
nitrate  of  different  strength,  or  a  long  tin  rod  in  two  solutions  of 
stannous  chloride  of  different  strength  placed  one  on  the  other,  in 
which  case  the  tin  rod  forms  at  the  same  time  both  electrodes  and 
the  metallic  circuit  between  them. 

In  this  case  the  electricity  is  produced  by  the  precipitation  of  the 
cations  of  the  concentrated  solution  as  metal  on  the  one  electrode,  to 
which  they  give  up  their  electric  charge  and  electrify  this  electrode  posi- 
tively, while  in  the  dilute  solution  from  the  material  of  the  other  electrode 
cations  pass  out  into  the  solution,  which  charges  this  electrode  negatively, 
since  positive  electricity  cannot  be  produced  without  the  formation  of 
an  equal  quantity  of  negative  electricity. 

The  number  of  cations  which  are  driven  out  from  the  given  electrode 
by  the  solution  pressure   of  the  metal  can  be  only  very  small  even  in 


90  GENERAL  CHEMISTRY, 

dilute  solutions,  since  a  condition  of  equilibrium  is  soon  brought  about 
from  the  fact  that  the  negatively  charged  electrode  exerts  such  an  at- 
traction on  the  positively  charged  ions  which  it  has  sent  out  that  just 
as  many  of  these  metal  ions  are  precipitated  again  on  the  negative  elec- 
trode as  metal  as  are  sent  out  by  the  electrode  into  the  solution,  and 
on  the  other  hand  the  attraction  exerted  by  the  negatively  charged 
electrolyte  on  the  electrode  which  it  has  charged  positively  is  of  such  a 
character  that  just  as  many  metal  ions  are  again  dissolved  as  the  elec- 
trolyte furnishes  to  the  metal. 

As  soon,  however,  as  the  electricity  is  allowed  to  flow  away  through 
a  conducting  wire  the  metal  again  drives  cations  into  the  solution  and 
the  solution  drives  cations  on  to  the  given  electrode  and  this  continues 
until  both  liquids  have  become  of  equal  concentration,  namely  until  the 
solution  pressure  and  the  osmotic  pressure  have  become  equally  great. 
Therefore  from  the  silver  or  tin  rod  which  dips  into  the  given  dilute  solu- 
tion, silver  or  tin  will  be  dissolved,  while  on  the  silver  or  tin  rod  in  the 
given  concentrated  solution,  silver  or  tin  will  be  precipitated  from  the 
solution  of  the  given  salt. 

Voltaic  cells  are  formed  when  two  rods  of  different  metals  dip 
into  solutions  of  their  salts,  which  must  contain  the  same  anion,  and 
the  two  solutions  are  in  contact.  This  is  the  case  when  the  solutions 
are  separated  by  a  porous  partition,  for  example,  a  porous  earthen- 
ware cylinder.  A  zinc  sulphate  solution  in  which  dips  a  zinc  rod, 
in  contact  with  a  copper  sulphate  solution  in  which  dips  a  copper 
rod,  forms  a  Daniell's  cell. 

The  electricity  is. produced  as  follows:  The  metal  with  the  greater 
solution  tension  (the  zinc)  dispatches  its  atoms  as  cations  into  the  elec- 
trolyte and  becomes  the  anode,  while  on  the  metal  with  the  lower  solution 
tension  (the  copper)  the  cations  are  precipitated  from  the  neighboring 
solution,  so  that  it  becomes  cathode.  If  the  electrodes  are  now  con- 
nected by  a  wire  an  equalization  of  opposite  electricities,  namely,  a 
current,  is  produced,  which  continues  until  all  the  zinc  of  the  anode  has 
dissolved  to  f orni  zinc  sulphate  or  all  of  the  copper  of  the  copper  sulphate 
solution  is  precipitated  on  the  cathode.  The  chemical  process  here 
involved  is  the  replacing  of  the  copper  in  the  copper  sulphate  by  the 
zinc,  which  therefore  itself  dissolves  in  equivalent  quantities.  Since 
the  cations  are  discharged  on  the  cathode  this  is  also  called  the  diverting 
electrode,  while  the  anode,  provided  that  anions  separate  at  it  which 
dissolve  the  anode  metal,  is  called  the  solution  electrode. 

Since  the  osmotic  pressure  of  the  ions  of  a  metal  operates  to  oppose 
its  solution  tension,  therefore  even  in  the  Daniell's  element  the  concen- 
tration of  the  electrolyte  must  be  of  importance.  If  the  concentration 
of  the  zinc  sulphate  solution,  namely  of  the  zinc  ions,  is  increased  then 
the  tendency  of  the  zinc  to  form  zinc  ions  is  decreased  and  the  anode 
becomes  less  anodic,  i.e.,  the  tension  of  the  cell  decreases.  If  the  concen- 
tration of  the  copper  sulphate  solution  is  increased,  which  is  equivalent 
to  an  increase  in  the  concentration  of  the  copper  ions,  then  the  tendency 
of  the  copper  ions  to  pass  over  to  the  cathode  is  increased  and  this  becomef 
more  cathodic,  i.e.,  the  tension  of  the  element  rises. 


PHOTOCHEMISTRY.  91 


PHOTOCHEMISTRY 

is  the  study  of  the  relation  between  chemical  energy  and  radiant 
energy. 

I.  Transformation  of  Chemical  Energy  into  Radiant  Energy. 

When  chemical  change  is  accompanied  by  the  development  of 
light  it  is  called  combustion  (see  Oxygen).  In  this  process  a  part 
of  the  chemical  energy  of  the  reacting  substances  is  set  free  as  heat 
and  light,  generally  the  light  first  appears  as  heat  which  raises  the 
temperature  of  the  substances  so  high  that  they  radiate  visible  light. 
Light  can  also  result  from  the  direct  transformation  of  chemical 
energy  (chemical  luminosity),  as  is  illustrated  by  the  brilliancy  ojf 
burning  magnesium,  the  temperature  of  which  is  only  about  1350°  but 
wliich  would  have  to  be  5000°  if  the  enormous  development  of  fight 
depended  on  the  temperature  alone.  The  light  produced  by  self- 
luminous  organisms  (beetles,  bacteria)  also  depends  on  chemical 
luminosity,  since  these  show  no  elevation  of  temperature. 

Many  substances  burn  with  a  flame,  many  only  with  glowing; 
the  flame  is  gas  heated  to  incandescence  by  the  combustion  process  and 
therefore  only  those  substances  burn  with  a  flame  which  are  com- 
bustible gases  or  which  develop  combustible  gases  from  their  own 
combustion. 

For  example,  pure  carbon  and  iron  burn  only  with  incandescence  since 
they  form  no  combustible  gases.  Wood,  coal,  tallow,  etc.,  bum  with  a 
flame  because  from  the  effect  of  the  heat  they  produce  gaseous,  com- 
bustible decomposition  products. 

Flames  can  be  luminous  or  non-luminous;  the  luminosity  is 
caused  by  the  presence  of  incandescent  solid  substances  in  the  flame 
and  also  by  an  increase  in  the  temperature  and  density  of  the  burning 
gases. 

A  non-luminous  flame  can  become  luminous  when  solid,  non-volatile 
substances  are  introduced  into  it  (for  example,  the  Welsbach  light)  and 
therefore  all  flames  are  luminous  when  the  products  of  combustion  are 
soUd  as  well  as  gaseous.  Zinc  and  magnesium  bum  with  luminous  flames 
because  the  oxides  which  they  form  on  burning  are  not  volatile  and 
when  finely  divided  are  heated  to  a  white  heat  in  the  flame.  When 
hydrogen  and  oxygen  are  compressed  together  they  bum  with  a  luminous 
flame  because  the  density  of  the  flame-gases  is  then  greater. 

If  gases  which  ordinarily  burn  with  a  luminous  flame  are  cooled  they 
lose  their  light-producing  power  and,  vice  versa,  non-luminous  gases 
become  luminous  when   they   are   previously  warmed.   For  example,  if 


92  GENERAL  CHEMISTRY. 

gases  which  are  not  combustible  or  which  do  not  support  combustion 
(nitrogen,  carbon  dioxide)  are  mixed  with  gases  which  burn  with  a  lumin- 
ous flame,  then  on  burning  the  mixture  no  light  is  developed.  This  is 
due  to  the  dilution  of  the  combustible  gases  and  to  the  coohng  caused 
by  the  non-combustible  gases  added. 

Many  substances  which  burn  in  the  air  with  a  non-luminous  flame 
burn  in  pure  oxygen  with  a  luminous  flame,  since  in  the  latter  case  the 
flanie  is  not  cooled  by  the  inert  nitrogen  of  the  air  and  therefore  reaches 
a  higher  temperature  and  further  because  the  products  of  combustion 
in  vessels  cannot  escape  so  rapidly  with  the  removal  of  heat  as  in  the 
open  air. 

The  luminosity  of  the  ordinary  illuminating  materials  is  due  to  the 
fact  that  finely  divided  carbon  separates  out  in  them  and  is  heated 
to  a  white  heat.  This  can  be  demonstrated  by  holding  a  cold  object 
in  the  flame  and  observing  the  carbon  which  is  deposited  on  it  as  soot. 

In  the  Welsbach  light  a  fabric  composed  of  99  per  cent,  thorium 
and  1  per  cent,  cerium  is  heated  in  a  non-luminous  flame  to  incan- 
descence. 

The  flame  of  marsh-gas  (CH^)  is  non-luminous;  the  flame  of  acetylene 
(CgHg) ,  on  the  contrary ,  is  very  brilliant  because  it  contains  twice  as  much 
carbon  in  the  molecule  as  the  former,  and  this  great  quantity  of  carbon, 
if  too  much  oxygen  does  not  reach  the  flame,  does  not  burn  immediately 
but  separates  out  in  a  finely  divided  state  and  becomes  white  hot. 

Marsh-gas,  hydrogen  gas,  and  carbon  monoxide  gas  burn  with  non- 
luminous  flames  because  their  products  of  combustion  are  exclusively 
of  a  gaseous  nature. 

Flames  consist  of  an  envelope  of  glowing  gas,  while  in  the  interior 
of  the  flame  (because  of  a  lack  of  that  gas  wliich  surrounds  the  flame 
and  maintains  it)  no  combustion  and  accordingly  no  high  temperature 
can  exist;  the  interior  of  the  flame  consists  of  unburned  gas  and  is 
cold. 

The  ordinary,  luminous  flame  consists  of  three  parts:   the  inner  dark 

Eart  consists  of  the  gases  still  unburned  (hydrocarbons,  especially  acety- 
!ne)  which  are  formed  from  the  decomposition  of  the  wax  or  tallow, 
etc.,  by  the  heat;  then  comes  a  luminous  mantle  in  which  incomplete 
combustion  occurs.  In  this  layer  ethylene  (CgH^)  splits  up  into  marsh 
gas  (CH^)  and  carbon  (C);  the  former  burns  completely  while  the  sepa- 
rated carbon  is  heated  to  incandescence  because  not  enough  oxygen 
is  present  for  its  combustion.  This  part  is  called  the  reducing  flame 
because  substances  which  contain  oxygen  when  introduced  into  it  give 
up  their  oxygen  to  the  carbon. 

In  the  external,  non-luminous,  bluish  layer,  which  is  surrounded 
by  air,  complete  combustion  of  the  separated  carbon  to  carbon  dioxide 
takes  place.  The  bluish  color  is  due  to  the  carbon  monoxide  which 
burns  here  to  carbon  dioxide.  This  part  is  called  the  oxidizing  flame, 
because  bodies  introduced  into  it  are  oxidized. 


PHOTOCHEMISTRY,  93 

The  temperatures  of  the  different  flames  are  very  different  and 
do  not  depend  on  the  luminosity,  as  is  shown  by  the  hardly  visible 
oxy hydrogen  flame  (see  Water). 

If  a  sufficient  quantity  of  air  is  introduced  into  the  interior  of  an 
illuminating-gas  flame,  then,  because  of  the  complete  combustion  of  the 
carbon,  and  also  because  of  the  dilution  (p.  92),  the  flame  becomes  non- 
luminous;  the  temperature  of  the  flame,  however,  becomes  noticeably 
higher.  On  this  depends  the  construction  of  the  Bunsen  burner  used  in 
^.aboratories  in  which  a  mixture  of  gas  and  air  is  burned. 

The  use  of  the  blowpipe,  a  metal  tube  through  which  air  is  blown 
into  the  flame  and  which  directs  this  side  wise  upon  the  object  to  be 
heated,  depends  on  the  same  principle.  This  has  an  oxidizing  action 
on  substances  held  in  the  outer  part  of  the  flame,  since  an  excess  of  oxy- 
gen is  here  present,  and  a  reducing  action  of  substances  held  in  the  inner, 
luminous  flame,  since  this  contains  free  carbon  or  reducing  hydrocarbons. 

Many  salts  impart  a  coloration  to  a  non-luminous  flame  (since 
the  salts  are  decomposed  and  reduced  by  the  flame  and  the  metal 
passes  over  into  the  gaseous  state),  which  is  characteristic  for  the 
metal  of  the  given  salt.  For  example,  the  salts  of  sodium  color 
the  flame  yellow,  the  salts  of  potassium  color  it  violet,  the  salts  of 
barium  color  it  green,  etc.,  so  that  in  this  manner  many  elements 
can  be  detected  in  their  compounds.  If,  however,  a  number  of  ele- 
ments which  color  the  flame  are  present,  then  the  color  of  one  ele- 
ment can  conceal  that  of  another,  but  in  such  a  case  all  of  the  elements 
present  can  be  detected  from  the  spectra  of  their  gases  (p.  44). 

Glowing  gases  send  out  rays  of  definite  wave  length  depending 
on  the  chemical  nature  of  the  given  gas,  but  which  are  independent 
of  the  temperature  within  wide  limits,  and  which  show  character- 
istic lines  when  split  up  by  a  prism  (p.  45). 

2.  Transformation  of  Radiant  Energy  into  Chemical  Energy. 

The  radiant  energy  of  light  can  cause  chemical  changes  which 
are  called  photochemical  reactions.  Radiant  energy  shows  con- 
siderable analogy  to  electrical  energy;  for  example,  the  metals  are 
more  or  less  positively  electrified  in  ultraviolet  light,  and  the  action 
of  hght  converts  selenium  and  phosphorus  into  modifications  which 
conduct  electricity. 

Photochemical  reactions  are  exothermic  or  endothermic;  in  the 
former  (since  no  energy  is  consumed,  but  is  set  free  as  heat)  the  light 
appears  only  to  start  the  chemical  process  and  to  accelerate  it  in  the 
manner  of  a  catalytic  agent;  in  the  latter  case,  at  all  events,  the  energy 


94  GENERAL  CHEMISTRY, 

of  the  radiation  changes  into  chemical  energy.  When  hght  causes  a 
chemical  process  it  must  always  be  absorbed  by  the  substance  on 
which  it  acts,  since  neither  the  transmitted  nor  the  reflected  part  of 
the  hght  produces  any  chemical  action. 

Through  investigations  conducted  with  the  so-called  actinometer  (see 
below)  it  has  been  found  that  the  chemical  action  is  proportional  to  the 
strength  of  the  light,  and  the  photochemical  effect  of  the  absorbed  light 
rays  is  in  general  proportional  to  the  quantity  of  light,  i.e.,  the  product 
of  the  intensity  and  time  of  radiation. 

Different  rays  of  light  have  different  action;  red  rays  are  in  many 
cases  inactive,  while  blue  and  violet  rays,  and  especially  the  invisible  ultra- 
violet rays,  exert  a  strong  chemical  action.  The  assimilation  of  carbon 
dioxide  in  plants  is  strongest  in  red  and  yellow  light,  so  that  the  character 
of  ray  which  can  cause  the  strongest  chemical  action  is  very  different 
in  different  chemical  reactions.  The  observation  that  the  chemical 
action  of  light  does  not  generally  reach  its  greatest  intensity  immediately 
on  absorption,  but  only  after  some  time,  is  caUed  photochemical  induction. 

The  photochemical  action  of  light  comprises  chemical  combination 
(for  example,  the  formation  of  HCl  from  H  +  Cl,  which  is  used  in  actino- 
metric  measurements),  chemical  decomposition  (for  example,  the  pro- 
duction of  dark-colored  halogen  compounds  of  silver  from  the  white  or 
yellow  halogen  compounds  of  silver  by  a  partial  splitting  off  of  halogen, 
on  which  depends  their  use  in  photography  and  actinometric  measure- 
ments), allotropic  transformation  (for  example,  the  production  of  red 
phosphorus  from  yellow) ,  and  the  reduction  or  oxidation  of  certain  sub- 
stances. 

The  most  important  photochemical  process  is  the  assimilation  of 
plants  containing  chlorophyll  under  the  influence  of  sunlight,  by  which 
the  radiant  energy  of  the  sun  is  stored  up  in  the  form  of  chemical  energy. 
In  this  process  the  carbon  dioxide  (COg)  taken  up  from  the  air  bv  the 
plants  is  reduced  with  the  evolution  of  oxygen  and  the  carbohydrates 
(sugar,  starch,  etc.)  rich  in  energy  are  formed. 

On  the  other  hand,  the  sun's  rays  also  retard  the  vital  functions  of 
those  plants  which  do  not  contain  chlorophyll  (the  fungi)  and  often  are 
fatal  to  them  (for  example,  the  pathogenic  bacteria).  Many  natural  and 
artificial  coloring  materials  are  bleached  by  light,  while  on  the  other  hand 
the  action  of  light  causes  many  other  substances  to  turn  darker  (for 
example,  white  paper  made  from  wood-pulp,  the  human  skin). 


PAET  SECOND. 
INORGANIC    CHEMISTRY. 


DIVISION  OF  THE  ELEMENTS. 

Ordinarily  the  elements  are  divided  into  two  groups,  the  non- 
metals  or  metalloids  and  the  metals. 

The  metals,  when  compact,  have  the  well-known  metallic  appear- 
ance and  are  good  conductors  of  heat  and  electricity;  they  do  not 
as  a  rule  combine  with  hydrogen,  producing  non- volatile  compounds. 
Their  oxygen  compounds  generally  have  the  character  of  basic  anhy- 
drides, i.e.,  they  form  bases  with  water  (p.  99,  b).  Many  metals  are 
soluble  in  water  when  in  a  finely  divided  state  (p.  54),  while  no  metal 
is  soluble  in  other  solvents  without  undergoing  a  change.  The  com- 
pounds of  the  metals  with  the  non-metals  are  decomposed  by  the 
electric  current,  the  metal  separating  out  at  the  negative  pole. 

The  non-metals  or  metalloids  are  (with  the  exception  of  hydro- 
gen) poor  conductors  of  heat  and  electricity  or  are  non-conductors,  and 
all  combine  with  hydrogen,  forming  volatile  generally  gaseous  com- 
pounds. Most  of  the  oxygen  compounds  of  the  non-metals  have  the 
character  of  acidic  anhydrides,  i.e.,  they  form  acids  with  water  (p.  98,  a). 
Most  of  the  non-metals  are  soluble  without  change  in  most  solvents. 
Their  compounds  mth  metals  are  always  decomposed  by  the  electric 
current,  so  that  the  non-metal  separates  at  the  positive  pole. 

A  sharplv  defined  division  of  the  elements  into  metals  and  non-metals 
is  not  possible  because  often  bodies  are  separated  which  have  great  simi- 
larity in  all  their  chemical  properties.  Thus  gaseous  hydrogen  is  .closely 
related  in  its  chemical  behavior  to  the  metals,  while  arsenic  and  antimony 
have  a  metallic  appearance,  but  behave  chemically  like  the  metalloids; 
also  various  elements  like  carbon  and  phosphorus  are  known  m  the  metallic 
as  well  as  the  non-metallic    condition.     It  is    therefore  indispensable 

95 


96  INORGANIC  CHEMISTRY. 

in  the  classification  to  consider  also  the  chemical  properties  and  to  divide 
the  elements  which  are  chemically  analogous  in  certain  groups.  This 
may  be  done  best  according  to  the  periodic  system,  which  classification 
will  be  followed  in  the  following  description  of  the  elements. 

NOMENCLATURE. 

1.  Radicals  or  Groups 

are  those  unsaturated  complex  groups  which  behave  like  the  ele- 
ments,  that  is,  they  form  permanent  constituents  of  a  series  of  com- 
pounds, and  in  these  they  can  be  replaced  by  other  equivalent  atoms 
or  groups  of  atoms;  thus  the  residue  ~0H  forms  a  constituent  of 
the  following  compounds:  KOH,  CaCOH)^,  Fe(0H)3,  Sn(OH)„  and 
can  be  transformed  unchanged  from  one  compound  into  another. 

The  corresponding  atomic  complexes  containing  carbon  are 
generally  called  radicals  and  all  the  others  groups  or  residues.  The 
group  ~0H  is  called  hydroxyl,  ~NH2  amido  or  amid,  =NH  imido  or 
imid,  -SH  hydrosulphuryl,  "NOj  nitro.  The  radical  =C0  is  called 
carhonyl,  "CHg  methyl,  ~CN  cyanogen,  etc. 

As  the  valence  of  the  elements  is  constant  towards  hydrogen,  the 
groups  which  are  obtained  by  removing  one  or  more  atoms  of  hydrogen 
from  the  saturated  molecule  cannot  exist  in  the  free  state,  but,  like  the 
atoms,  unite  together  with  their  free  valences,  forming  complicated 
bodies;  thus  from  the  molecule  of  water,  HOH,  of  hydrogen  sulphide, 
HSH,  of  marsh-gas,  CH^,  by  the  removal  of  an  atom  of  hydrogen  we 
obtain  the  univalent  groups  -OH,  -SH,  -CH3,  which  immediately  unite, 
forming 

II        II  II      II  IV      IV 

HO-OH,  HS-SH,  H3C-CH3, 

Hydrogen  peroxide  Hydrogen  persulphide.  Dimethyl  or  ethane. 

In  regard  to  other  facts  about  nomenclature  see  Part  III. 

2.  Binary  Compounds. 

These  are  compounds  consisting  of  two  elements  and  are  desig- 
nated by  names  of  the  elements  following  each  other  with  the 
final  word  terminating  in  ide;  thus  all  binary  compounds  of  oxygen, 
sulphur,  chlorine,  bromine,  iodine,  fluorine,  are  called  oxides,  sul- 
phides, chlorides,  bromides,  iodides,  fluorides,  while  the  metallic 
compounds  of  hydrogen,  boron,  phosphorus,  nitrogen,  carbon,  silicon 
are  called  hydrides,  borides,  phosphides,  nitrides,  carbides,  silicides. 
Thus: 

CaO,  ZnS;  AlF.,  HCl, 

Calcium  oxide.       Zinc  sulphide.      Aluminium  fluoride.     Hydrogen  chloride. 


PA, 

P,0„ 

PA, 

hosphorus 

Phosphorus 

Phosphorus 

trioxide. 

tetroxide. 

pentoxide. 

NOMENCLATURE.  97 

If  two  different  compounds  of  the  same  elements  are  known, 
we  designate  that  compound  having  the  element  with  highest  valence 
by  the  suffix  ic  to  the  Latin  root  of  the  metal,  while  the  one  having 
the  element  with  lower  valence  terminates  in  ous.     Thus : 

HgCl,  HgCl,,         Hg,0,         HgO,         hJ^S,  HgS, 

Merciirous  Mercuric        Mercurous       Mercuric        Mercurous         Mercuric 

chloride.  chloride.  oxide.  oxide.  sulphide.  sulphide. 

These  compounds  used  to  be  indicated  by  the  prefixes  proto  and  per. 
Thus: 

HgCl,  HgCl^,  FeCl^,  FeCl,, 

Mercury  Mercury  Iron  Iron 

protochloride.  perchloride.  protochloride.  perchloride. 

If  more  than  two  compounds  are  known  of  the  same  elements, 
then  the  number  of  oxygen,  chlorine,  bromine,  etc.,  atoms  contained 
in  the  molecule  are  indicated  by  the  Greek  prefixes.     For  example: 

HjO,  H2O2, 

Hydrogen  Hydrogen 

monoxide.  dioxide. 

CJompounds  like  CtjOj  have  the  prefix  sesqui  to  differentiate  them 
from  the  trioxides  such  as  CrOg.  The  different  steps  in  oxidation  are 
often  indicated  as  follows:  suboxide,  oxide,  sesquioxide  and  super-  or 
peroxide.  Thus:  Pb^O,  lead  suboxide;  PbO,  lead  oxide;  PbjOg,  lead 
sesquioxide;  Pb02,  lead  superoxide  (also  lead  peroxide). 

3.  Ternary  and  Higher  Compounds. 

The  most  important  compounds  belonging  to  this  group  are  the 
acids,  bases,  and  salts  which  have  the  property  in  common  of  being 
electrolytes,  which  has  already  been  discussed  from  the  standpoint  of 
the  theory  of  ions,  p.  84. 

A.  Acids. 

Acids  are  compounds  of  hydrogen  with  non-metals  and  also  with 
certain  metals,  this  hydrogen  being  entirely  or  partly  replaceable  by 
the  metal  on  coming  in  contact  with  a  metal  or  a  metallic  hydroxide 
(a  base)  or  with  a  metallic  oxide  (a  basic  anhydride),  producing  com- 
pounds of  the  metal  called  salts.     Thus: 

2HC1      +        Zn        =       ZnCl^     +       2H 
?^l'oSr  Zinc.  ,£«de.  Hydrogen. 


H,S04 

Sulpnuric 
acid. 

II 

+       ZnO       = 

Zinc 
oxide. 

=      ZnS04 

Zinc 
sulphate. 

HNO3 

Nitric 
acid. 

+    NaOH     = 

Sodium 
hydroxide. 

=     NaNOj 

Sodium 
nitrate. 

INORGANIC  CHEMISTRY. 

+     HOH 

Water. 

+      HOH 
Water. 

Acids,  when  soluble  in  water,  have  a  sour  taste  and  acid  reaction 
(p.  84).  According  to  composition  we  differentiate  between  oxygen 
free  acids  and  those  which  contain  oxygen  (oxyacids),  and  they  are 
called  mono-,  di-,  tri-,  etc.,  basic  (mono-,  di-,  tri-,  etc.,  valent  or 
mono-,  di-,  tri-,  etc.,  hydric)  acids  according  to  whether  they  contain 
one,  two,  three,  etc.,  atoms  of  hydrogen  replaceable  by  metals. 

Acid  anhydrides,  acidic  oxides  (also  incorrectly  called  anhydrous 
acids),  are  those  oxides  produced  by  removing  all  the  hydrogen  with 
the  corresponding  quantity  of  oxygen,  in  the  form  of  water,  from  one 
or  more  molecules  of  an  oxyacid;  for  example: 

H^SO,   =   SO3     +    H^O        2H3PO4  =     PA     +   3H2O 

Sulphuric     Sulphuric  Phosphoric       Phosphoric 

acid.         anhydride.  acid.  anhydride. 

In  the  same  manner  the  sulphoacids  yield  anhydrides  by  abstract- 
ing H^S;   thus,  2H3AsS3=As,S3+3H2S. 

The  acid  anhydrides  do  not  have  any  acid  reaction  and  unite 
with  water,  forming  acids  again. 

Acid  radicals  are  the  groups  obtained  on  the  removal  of  hydroxyl 
groups  OH  from  a  molecule  of  oxyacids  (often  do  not  exist  free); 
for  example: 

SO2  acid  radical  of  sulphuric  acid  S02(OH)2, 
NO2    "         "        "  nitric  "    NO,(OH), 

PO     "         "        "  phosphoric  "    P0(0H)3. 

Oxygen  free  acids  are  designated  by  adding  the  prefix  hydro  to 
the  element  or  group  forming  the  acid,  this  element  or  group  ending 
in  ic;  thus,  HCl,  hydrochloric  acid;  HBr,  hydrobromic  acid;  HCN, 
hydrocyanic  acid. 

The  sulphoacids  belonging  to  this  group  can  be  derived  from 
the  oxyacids  by  replacing  their  oxygen  by  sulphur  and  calling  them, 
correspondingly,  H3ASS4,  sulphoarsenic  acid;  HCNS,  sulphocyanic 
acid. 

The  name  of  the  oxyacids  is  derived  by  adding  the  word  acid 
to  the  name  of  the  element  or  group  forming  the  acid  endinir  in  ic; 


NOMENCLATURE.  99 

for  example,  HCIO3,  chloric  acid;   HCNO,  cyanic  acid;   HjS04,  sul- 
phuric acid;   H3ASO4,  arsenic  acid;   H4Si04,  silicic  acid. 

If  two  acids  of  the  same  elements  are  known  we  designate  the  one 
poorest  in  oxygen  with  the  termination  ous;  thus,  HjSOg,  sulphurous 
acid;  if  a  series  of  acids  of  the  same  elements  are  known,  the  one 
poorest  in  oxygen  has  the  prefix  hypo  (below),  while  the  richest  m 
oxygen  has  the  prefix  hyper  (above)  or  per;  thus : 

HCIO,  Hypochlorous  acid.  HCIO3,  Chloric  acid. 

HCIO2,  Chlorous  acid.  HCIO4,  Hyper  or  Perchloric  acid. 

If  an  acid  HCI2O5  was  known  it  would  stand  between  chlorous  acid 
and  chloric  acid  and  would  be  called  hypochloric  acid. 

The  oxyacids  of  nitrogen  are  called:  hyponitrous  acid,  HNO;  nitrous 
acid,  HNO2;  nitric  acid,  HNO3. 

B.  Bases. 

Bases  are  compounds  of  hydroxyl  groups  H0~  with  metals, 
which  on  coming  in  contact  with  an  acid  replace  its  hydrogen  entirely 
or  partly  by  the  metal  contained  in  it,  producing  compounds  of  the 
metal,  called  salts;  for  example: 

I  I 

+     HOH 

Water. 

When  soluble  in  water  the  bases  have  a  caustic  taste  and  have  an 
alkaline  reaction  (basic,  p.  84).  According  as  the  bases  contain  one, 
two,  three,  etc.,  hydroxyl  groups  they  are  called  mono-,  di-,  tri-,  etc., 
acidic  (mono-,  dl ,  tri-,  etc.,  valent  or  mono-,  di-,  tri-,  hydric  bases). 

Basic  anhydrides  are  those  oxides  which  are  produced  when  all 
the  hydrogen  combined  with  the  corresponding  quantity  of  oxygen 
as  water  is  removed  from  one  or  more  molecules  of  a  base;  for  example: 
2KOH  =  K20+H20;  Zn(OH)2  =  ZnO+H20;  2Fe(OH)3=Fe203+3H20. 

The  name  given  to  the  base  is  obtained  by  adding  the  word  hy- 
droxide  to  the  name  of  the  element  forming  the  base.  If  an  element 
forms  several  hydroxides  then  the  designation  is  the  same  as  the 
corresponding  oxides  (p.  97);  for  example:  Fe(0H)2,  ferrous  hydrox- 
ide; Fe(0H)3,  ferric  hydroxide. 

C.  Salts. 

Salts  are  the  compounds  produced  by  completely  or  partly  replac- 
ing the  hydrogen  of  an  acid  by  a  metal.  This  can  take  place  as  fol- 
lows: 


NaOH    + 

HNO3       = 

=     NaNOa 

Sodium 

Nitric 

Sodium 

hydroxide. 

acid. 

nitrate. 

100  INORGANIC  CHEMISTRY, 

By  replacing  the  hydrogen  of  the  acids  directly;  thus,  Zn+  H2SO4  = 
2H+ZnS04. 

By  the  acid  coming  in  contact  with  a  base  or  its  anhydride,  when 
a  double  decomposition  takes  place  with  the  formation  of  water;  thus: 

KOH   +  HCl  =  KCl  +  HOH; 

Ca(0H)2+  H2SO4  =  CaS04+  2H0H; 

CaO    +H2S04  =  CaS04+  HOH. 

By  an  acid  anhydride  combining  directly  with  a  basic  anhydride; 
thus,  Fe203+  3SO3  =  Fe^CSOJs. 

Normal  or  neutral  salts  are  those  which  are  obtained  when  all 
of  the  replaceable  hydrogen  in  an  acid  is  replaced  by  a  metal.  Most 
of  them  have  a  neutral  reaction  (p.  85) ;  still,  many  normal  salts  and 
indeed  acid  salts  ha-ve  an  alkaline  reaction  when  they  are  derived 
from  weak  acids;  on  the  other  hand  many  normal  salts  are  acid 
when  they  are  derived  from  weak  bases  (see  p.  86). 

In  giving  names  to  the  oxysalts  all  the  salts  containing  the  same 
salt-forming  element  are  given  a  generic  name  by  replacing  the 
last  syllable  of  the  Latin  name  of  the  acid-forming  element  by  the 
suffix  ate  for  those  richest  in  oxygen  and  the  suffix  ite  for  an  analo- 
gous compound  poorer  in  oxygen. 

For  example:  MClO       Hypochlorite 

MCIO2      Chlorite 

MCIO3     Chlorate 

MCIO4      Perchlorate 
The  special  name  is  formed  by  placing  the  name  of  the  metal  replacing 
the  hydrogen  before  the  generic  name.     For  example: 

KCIO       Potassium  hypochlorite 

NaClOg    Sodium  chlorite 

NaClOg    Sodium  chlorate 

AgClO^    Silver  perchlorate 

The  special  names  of  two  salts  which  contain  the  same  metal 
with  different  valence  are  derived  in  the  same  manner  as  the  oxides, 
bases,  etc.  (p.  97),  by  adding  ic  to  the  Latin  root  of  the  name  of 
the  metal  replacing  the  hydrogen  when  it  has  the  highest  valence 
and  ous  when  it  has  the  lowest  valence.    Thus: 

II  in 

FeSO*    Ferrous  sulphate;         Fe2(S04)8  Ferric  sulphate; 

I  n 

HgNOg  Mercurous  nitrate;        Hg(N08)2  Mercuric  nitrate; 

I  II 

CuCl      Cuprous  chloride;         CuCl,         Cupric  chloride. 


NOMENCLATURE.  101 

The  names  of  the  oxygen  free  salts  are  derived  by  adding  ide  to 
the  name  of  the  acid-forming  element;  for  example,  FeCl2,  ferrous 
chloride;  FeClj,  ferric  chloride;  KCN,  potassium  cyanide.  Sulpho- 
salts  (see  Sulphoacids,  p.  98)  and  complex  salts  (p.  102)  also  often 
terminate  with  the  syllable  ate;  thus,  KCNS  is  called  potassium 
sulphocyanide  or  potassium  sulphocyanate. 

Acid  salts  are  those  produced  when  only  a  part  of  the  replaceable 
hydrogen  in  a  polybasic  acid  is  replaced  by  a  metal.  Ordinarily 
they  have  an  acid  reaction,  but  still  they  may  be  neutral  or  alkaline 
in  reaction  when  they  are  derived  from  a  weak  acid  (p.  86). 

Certain  salts,  which  may  be  considered  as  a  combination  of  a  neutral 
salt  with  an  acid  anhydride,  are  often  called  erroneously  acid  salts;  thus 
the  potassium  salt  of  dichromic  acid,  K2Cr20y=K2CrO^  +  CrOj,  is  often 
called  acid  potassium  chromate. 

Acid  salts  of  dibasic  acids  are  named  by  adding  the  word  add 
or  the  prefix  bi  or  hydro  to  the  acid-forming  word;  for  example, 
NaHSOi,  acid  sodium  sulphate,  sodium  bisulphate,  sodium  hydrosul- 
phate. 

Acid  salts  of  tri-  and  polybasic  acids  are  named  according  to 
the  number  of  hydrogen  atoms  of  the  acid  replaced  by  metallic  atoms 
as  mono-,  primary,  monobasic;  or  as  di-,  secondary,  dibasic;  or  as 
tri-,  tertiary,  tribasic  salts,  etc.  Names  are  also  given  according  to 
the  number  of  hydrogen  atoms  left  that  are  replaceable  by  metals, 
as  follows :  simple,  double  salts,  etc.     For  example : 


TTTT  T>r\      n  /'H2PO4.    Mono-,  primary,  double  acid, 
KH^rO^.    ^a\^H,PO,.        monobasic 

K2HPO4.  CaHPO*.  Di-,  secondary,  simple  acid, 
dibasic 

K3PO4.  CaaCPOJj.  Tri-,  tertiary,  tribasic,  neu- 
tral 


o 

ill 

CO    o3    O 
P-l 


Basic  salts  are  those  which  are  obtained  when  a  metal  atom 
replaces  all  the  replaceable  hydrogen  in  an  acid  with  only  a  part 
of  its  valence,  while  the  remaining  valences  are  saturated  with  basic 
HO  groups  or  by  O  atoms.  They  are  designated  by  adding  the  word 
basic  or  the  prefix  sub  or  oxy  to  the  acid-forming  element;  thus 
(HO)  2  •"  Bi  -  NO3,  basic  bismuth  nitrate,  bismuth  subnitrate,  O =Sn =C1,; 
tin  oxychloride. 


102  INORGANIC  CHEMISTRY, 

Double  salts  are  those  salts  which  are  obtained  when  the  replace- 
able hydrogen  of  an  acid  is  replaced  by  different  metals — thus, 
NaMgP04,  sodium  magnesium  phosphate — or  by  the  combination  of 
several  molecules  of  simple  salts;  for  example,  MgS04+K2S04,  mag- 
nesium-potassium sulphate. 

Complex  salts  are  those  compounds  which  are  produced  by  the 
combination  of  simple  salts  and  which  differ  from  the  double  salts 
by  not  having  the  reactions  of  their  simple  constituents  (their  ionS; 
p.  83),  but  which  have  reactions  corresponding  to  the  atomic  com- 
plex composed  of  simple  constituents  (which  functionate  as  com- 
plex ions,  p.  84).  For  example,  by  the  union  of  2KCl+PtCl4  we  do 
not  obtain  the  double  salt,  but  the  potassium  salt  of  hydrochlorpla- 
tinic  acid,  HjPtCl,  (see  Platinum  and  Gold) ;  by  the  union  of  4KCN+ 
Fe(CN)j  the  potassium  salt  of  ferrocyanic  acid,  H4FeCeN,  (see  Cyan- 
ogen Compounds). 

The  double  salts  must  not  be  confounded  with  the  isomorphous 
mixtures  (p.  49)  obtained  on  the  common  crystallization  of  isomorphous 
salts  and  whose  composition  changes  with  the  changes  in  the  solution 
from  which  they  separate  out. 


I.    NON-METALS  OR  METALLOIDS. 

According  to  the  periodic  system  the  elements  belonging  to  this 
group  are  classified  as  follows: 


Hydrogen, 

Oxygen, 

Nitrogen,        HeUum, 

Carbon, 

Fluorine, 

Sulphur, 

Phosphorus,   Argon, 

Sihcon, 

Chlorine, 

Selenium, 

Arsenic,          Neon, 

Germaniumj 

Bromine, 

Tellurium. 

Antimony,      Krypton, 

Tin, 

Iodine. 

Bismuth,        Xenon. 

Lead. 

Univalent. 

Bivalent. 

Trivalent. 

Quadrivalent. 

The  elements  bismuth,  germanium,  tin,  and  lead,  which  have 
pronounced  metalhc  properties,  will  be  treated  of  in  connection  with 
the  metals. 

Hydrogen  hardly  belongs  to  either  of  the  above  groups,  as  it  has 
both  metalloid  and  metallic  characteristics,  and  forms  at  the  same 
time  the  type  of  all  elements. 


Hydrogen. 

Atomic  weight  1.01  =  H. 

Occurrence.  Free  in  small  quantities  in  gases  of  volcanoes  and 
certain  petroleum  wells,  enclosed  in  the  potassium  salts  of  Stass- 
furt,  in  the  rock  salt  of  Wieliczka,  and  in  the  meteoric  iron  of  Lenarto. 
In  the  decomposition  of  organic  substances  hydrogen  is  set  free; 
hence  it  occurs  in  the  intestinal  gases  of  man  and  certain  animals 
and  as  traces  in  the  atmosphere.  The  chief  quantity  of  hydrogen 
exists  in  combination  with  oxygen  as  water;  all  plants  and  animals 
contain  combined  hydrogen  as  a  chief  constituent.  As  shown  by 
spectral  analysis  free  hydrogen  exists  in  large  quantities  in  the  fixed 
stars  and  in  the  gases  surrounding  the  incandescent  solax  nucleus. 

103 


104  INORGANIC  CHEMISTRY. 

Preparation.  1.  Ordinarily  hydrogen  is  prepared  by  the  action 
of  hydrochloric  acid  or  dilute  sulphuric  acid  upon  zinc  or  iron: 

Zn     +     HSO,     =     ZnS04     +     H^. 

Zinc.       Sulphuric  acid      Zinc  sulphate      Hydrogen. 

On  using  strong  sulphuric  acid  the  generation  of  hydrogen  soon  ceases 
on  account  of  the  formation  of  zinc  sulphate,  which  is  not  soluble  in  strong 
sulphuric  acid  and  which  forms  a  protective  coat  on  the  zinc  which  only 
dissolves  on  the  addition  of  water.  Pure  zinc  is  only  shghtly  acted 
upon  by  dilute  acids,  but  if  small  amounts  of  certain  salts  of  the  heavy 
metals  (platinum,  copper,  silver,  lead,  etc.)  are  added  to  the  acid,  a  rapid 
evolution  of  hydrogen  takes  place.  The  conversion  of  the  H  ions  of 
the  acid  into  hydrogen  gas  takes  place  on  the  surface  of  the  zinc  with 
greater  difficulty  than  on  the  surface  of  other  metals,  hence  on  the  ad- 
dition of  salts  of  other  metals  the  respective  metal  is  precipitated  on 
the  surface  of  the  zinc  and  the  hydrogen  is  therefore  evolved  with  greater 


2.  By  the  electrolysis  of  water  (HgO)  to  which  some  acid  or 
base  has  been  added,  when  the  water  is  apparently  directly  decom- 
posed (p.  75),  2  vol.  hydrogen  are  simultaneously  evolved  at  the 
negative  pole  and  1  vol.  oxygen  at  the  positive  pole. 

3.  By  the  decomposition  of  water  by  many  metals  (p.  113)  either 
at  high  temperatures  or  even  at  ordinary  temperatures.  The  alkali 
and  alkahne-earth  metals  (which  see),  such  as  potassium,  sodium, 
calcium,  decompose  water  even  in  the  cold: 

2H0H     +     2Na     =     2NaOH     +     H^. 

Water  Sodium     Sodium  hydroxide.   Hydrogen. 

Compact  zinc,  iron,  etc.,  decompose  steam  only  at  a  red  heat  (p.  61) : 
3Fe+.4HOH     -     Fe304    +     4Hj. 

Ferrous-ferric  oxide. 

Red-hot  carbon  also  decomposes  water  (see  Carbon  Monoxide), 
and  metallic  magnesium  decomposes  water  at  its  boiling-point. 

4.  Very  pure  hydrogen  can  be  prepared  by  heating  sodium  formate 
(see  Formic  Acid)  with  sodium  hydroxide :  CHNaOj  +  NaOH  =  Na^CO,  +  R,. 

5.  Finely  powdered  zinc,  aluminium,  iron,  evolve  hydrogen  on 
warming  with  caustic  alkah :  Zn  +  2NaO  H=  Zn  (0Na)2  +  H j.  Al  +  3K0H 
^A1(0K),  +  3H. 

Technical  Preparation.  1.  By  heating  calcium  hydroxide,  Ca(0H)2, 
with  powdered  zinc  or  iron:  Zn+Ca(OH)2=ZnO-f'CaO  +  H2,  or  with 
carbon:    2Ca(OH)2  +  C=CaO  +  CaC03  +  2H2. 

2.  Hydrogen  is  obtained  in  the  electrolysis  of  water  (see  above) 
or  as  a  by-product  in  the  preparation  of  potassium  hydroxide  from  a 


HYDROGEN.  105 

potassium  chloride  solution  by  electrolysis  when  potassium  hydroxide  is 
formed  at  the  negative  pole  and  hydrogen  evolved,  while  chlorine  gas 
is  set  free  at  the  positive  pole: 

2KC1  +  2H20=  2K0H  +  Hj  +  Cl^ 

Properties.  Colorless,  odorless,  and  tasteless  gas,  slightly  soluble 
in  water  and  liquefiable  at  —242°  (p.  41)  to  a  colorless  liquid  having 
a  sp.  gr.  0.07.  When  allowed  to  evaporate  under  the  air-pump  the 
temperature  sinks  to  —252°  and  the  remaining  liquid  solidifies  to  an 
ice-like  mass.  At  this  lowest  obtainable  temperature  all  gases  and 
liquids  solidify,  hence  on  introducing  them  in  evaporating  liquid 
hydrogen  they  liquefy  or  solidify. 

Hydrogen  gas  is  the  lightest  of  all  substances;  one  liter  weighing 

0.0899  g.  at  0°  and  760  mm.  (p.  42).     As  a 'liter  of  air  weighs  1.293  g. 

1  293 
at  0°  and  760  mm.,  then  hydrogen  gas  weighs  -  1^^      that  of  air  or  is 

14.4  times  lighter  than  air,  and  its  sp.  gr.  relative  to  air  as  standard  is 

0  0899 

— or  0.0695.     (In  regard   to  the   calculation   of  the   absolute 

weight  and  specific  gravity  of  gases  from  their  molecular  weight  see 
p.  43). 

When  ignited,  hydrogen  burns  in  the  air  into  water  with  a  non- 
luminous  bluish  flame  which  is  very  hot  (p.  112).  If  a  narrow  cylin- 
der, open  at  both  ends,  be  held  over  a  small  hydrogen  flame,  a  sound 
is  produced  by  the  vibrations  of  the  heated  air  (chemical  harmonica; 
also  produced  by  other  burning  gases). 

If  hydrogen  (or  other  combustible  gas)  is  passed  in  the  air  over 
finely  divided  platinum  or  palladium  (spongy  platinum,  palladium 
asbestus),  it  inflames  spontaneously  (Dobreiner's  lamp,  gas-Hghters) 
because  the  metal  in  the  finely  divided  state  has  the  property  of  con- 
densing the  gases  so  that  their  reaction  activity  is  increased;  hence 
they  combine  and  the  metal  becomes  incandescent  and  ignites  the 
excess  of  the  gaseous  mixture  (Catalysis,  p.  66). 

A  mixture  of  hydrogen  with  oxygen  or  with  air  is  called  "detonat- 
ing gas,"  as  it  explodes  on  ignition.  Hydrogen  should  therefore  be 
ignited  only  when  all  the  air  has  been  expelled  from  the  generating 
apparatus. 

Many  metals  combine  with  hydrogen,  forming  so-called  hydrides, 
of  which  potassium  and  sodium  hydride  have  a  metallic  appearance, 


106  INORGANIC  CHEMISTRY. 

while  the  others  are  white  or  form  gray  powders.  Palladium  and 
platinum  condense  hydrogen  in  themselves  without  combining 
therewith  and  without  changing  their  appearance. 

Contrary  to  the  other  metalloids,  hydrogen  shows  great  conductivity 
for  heat  and  electricity,  a  property  which  is  generally  ascribed  only  to 
the  metals. 

Because  of  its  lightness  hydrogen  diffuses  (p.  46)  readily  through 
animal  or  vegetable  membranes,  also  through  red-hot  tubes  of  iron, 
platinum,  palladium,  which  do  not  allow  other  gases  to  pass  through. 

On  account  of  its  relationship  to  oxygen  (p.  112)  hydrogen  abstracts 
oxygen  from  many  oxygen  compounds  either  in  the  presence  of  heat 
or  in  the  nascent  state  with  the  formation  of  water.  This  conversion 
of  a  compound  rich  in  oxygen  into  a  compound  poorer  or  free  from 
oxygen  is  called  reduction. 

By  reduction  we  also  understand  the  introduction  of  hydrogen 
as  well  as  the  replacement  of  oxygen  by  hydrogen. 

OXYGEN  GROUP. 

Oxygen,  Sulphur,  Selenium,  Tellurium. 

The  members  of  this  group  are  bivalent,  although  the  last  three  also 
occur  as  quadrl-  and  sexivalent  elements.  They  show  great  similarity 
to  each  other.  With  increase  in  atomic  weight  the  specific  gravity, 
melting-  and  boiling-points  also  increase,  and  their  properties  become 
more  and  more  metallic.  All  four  elements  form  combinations  with 
2  atoms  of  hydrogen  which,  with  the  exception  of  water,  HjO,  are  gases 
at  the  ordinary  temperature  and  have  acid-like  characters.  In  regard 
to  the  relationship  of  the  members  of  this  group  to  the  elements  of  the 
chromium  group  we  refer  to  this  grou" 

I.  Oxygen. 

Atomic  weight  16=0. 

Occurrence.  Free  in  the  atmosphere  (21  vols,  per  cent.);  com- 
bined in  water  in  most  animal  and  vegetable  tissues,  as  well  as  in  min- 
erals, so  that  about  one-half  of  the  weight  of  our  planet  consists  of 
this  element. 

Preparation.  1.  Ordinarily  by  heating  potassium  chlorate 
(KCIO3)  which  decomposes  into  potassium  chloride  and  oxygen: 
KC103  =  KCl-h03. 

2.  By  the  electrolysis  of  water  to  which  some  acid  or  base  has 
been  added  (p.  104)  when  1  vol.  oxygen  is  liberated  at  the  positive 


OXYGEN.  107 

pole  and  as  the  same  time  2  vols,  hydrogen  are  evolved  at  the  nega- 
tive pole  (p.  75). 

3.  By  strongly  heating,  many  compounds  rich  in  oxygen,  i.e., 
mercuric  oxide  (HgO)  which  decomposes  into  mercury  and  oxygen: 
HgO  =  Hg+0;  manganese  dioxide  (Mn02),  which  is  converted  into 
manganese  superoxide  and  gives  off  oxygen,  3Mn02  =  Mn304-|-20; 
and  barium  dioxide  (BaOj),  which  decomposes  into  barium  monoxide 
and  oxygen:   BaOi  =  BaO+0. 

4.  By  heating  many  substances  rich  in  oxygen,  such  as  manganese 
dioxide,  barium  dioxide,  potassium  persulphate,  potassium  dichromate 
with  concentrated  sulphuric  acid,  or  by  heating  a  solution  of  chloride 
of  lime  with  a  cobalt  salt  or  copper  oxide  (see  these). 

5.  It  may  be  prepared  in  the  cold  by  the  action  of  water  upon  a 
mixture  of  barium  dioxide  and  potassium  ferri cyanide  or  by  the  action 
of  water  upon  alkali  superoxides  or  percarbonates;  of  hydrochloric 
acid  upon  a  mixture  of  barium  dioxide  and  manganese  dioxide;  of  chloride 
of  lime  or  potassium  permanganate  upon  hydrogen  peroxide,  etc.  (see 
these). 

Technical  Preparation.  1.  On  heating  barium  monoxide  (BaO) 
under  pressure  to  700°  in  a  current  of  air  it  is  converted  into  barium 
dioxide  (BaO^),  which  at  this  temperature  decomposes  into  barium 
monoxide  and  oxygen  when  the  pressure  is  diminished.  On  in- 
creasing the  pressure  and  passing  air  through  we  again  obtain 
barium  dioxide,  which  decomposes  as  above  stated  (p.  72).  (Brin 
process.) 

2.  Oxygen  is  evolved  on  heating  calcium  plumbate  (CajPbO^)  in 
carbon  dioxide  gas  (CO^):  Ca2Pb04  +  2C02=2CaC03  +  Pb  +  0,.  On  heat- 
ing the  residue  in  a  current  of  air  calcium  plumbate  is  re-formed (Kassner's 
method). 

3.  On  repeatedly  diminishing  the  pressure  on  liquefied  air  (p.  41) 
a  partial  evaporation  takes  place;  the  liquefied  nitrogen  evaporating 
more  rapidly  than  the  liquid  oxygen  on  account  of  its  lower  boiling- 
point,  1  aves  a  liquid  which  consists  of  about  80  per  cent,  oxygen. 

Properties.  Colorless,  odorless,  and  tasteless  gas,  slightly  soluble 
in  water,  1.105  times  heavier  than  air,  liquefiable  at -182°  to  a  light 
blue  Hquid  having  a  sp.  gr.  1.12  (p.  41)  and  which  solidifies  at  -252** 
to  an  icy  mass. 

One  liter  of  oxygen  gas  weighs  1.429  g.  at  0°  and  760  mm.;  hence 

1.429 
its  specific  gravity  relative  to  air  is    '  q^  =  1.105. 

The  atomic  weight  of  oxygen  =  16  serves  as  a  basis  for  the  deter- 
mination of  the  atomic  weight  of  the  other  elements,  and  the  molecular 


108  INORGANIC  CHEMISTRY. 

weight  of  oxygen  =  32  also  serves  as  the  basis  for  the  determination 
of  the  molecular  weight  of  all  other  bodies,  for  the  reasons  already- 
given  on  p.  17. 

A  glowing  piece  of  wood  or  coal  burns  in  oxygen  with  great  bright- 
ness; ignited  sulphur  burns  with  a  pale  blue  flame  into  sulphur  dioxide 
gas,  while  phosphorus  burns  with  a  dazzling  white  flame  into  solid 
phosphorus  pentoxide  (P2O5),  etc.  Many  objects,  such  as  heated  iron, 
which  do  not  burn  in  the  air,  burn  with  scintillations  in  oxygen 
into  oxides.  As  oxygen  is  the  constituent  of  the  air  which  supports 
combustion,  it  is  natural  that  bodies  should  burn  more  energetically 
in  pure  oxygen. 

Molten  silver  absorbs  22  times  its  volume  of  oxygen  which  it 
gives  off  on  cooling. 

All  elements,  with  the  exception  of  fluorine  and  those  of  the 
argon  group,  combine  with  oxygen.  This  process  is  called  oxidation, 
and  the  resulting  compounds  are  called  oxides. 

By  oxidation  we  also  understand  the  removal  of  hydrogen  by  oxygen 
from  a  compound  or  the  introduction  of  oxygen  in  place  of  hydrogen 
with  the  splitting  off  of  water. 

The  oxides  of  the  metalloids  are  nearly  always  acid  anhydrides 
(p.  98),  while  the  oxides  of  the  metals  are  nearly  always  basic  anhy- 
drides (p.  99). 

We  differentiate  also  between  indifferent  oxides  which  are  derived 
from  metalloids  and  metals,  but  which  form  neither  bases  nor  acids, 
but  still  combine  directly  with  acids,  forming  salts,  such  as  nitrous 
oxide,  nitric  oxide,  manganese  dioxide,  lead  suboxide,  lead  peroxide, 
etc. 

These  indifferent  oxides  are  those  compounds  called  suboxides  and 
peroxides.  These  latter  readily  give  off  oxygen,  hence  have  a  strong 
oxidizing  action.  With  hydrochloric  acid  they  either  evolve  hydrogen 
peroxide  or  set  chlorine  free.  Oxy acids  set  free  oxygen  when  they  act 
on  peroxides. 

Every  oxidation  is  a  chemical  process  connected  with  the  devel- 
opment of  heat.  If  the  oxidation  of  a  body  takes  place  very  rapidly, 
it  often  occurs  that  such  a  great  development  of  heat  is  evolved 
that  the  chemical  combination  takes  place  with  the  production  of 
light  and  the  body  is  popularly  said  to  burn.  In  ordinary  life  only 
such  bodies  are  said  to  be  combustible  which  burn  in  atmospheric 


OXYGEN.  109 

air  because  they  can  combine  with  the  oxygen  thereof  (combustion 
in  the  restricted  sense). 

If  the  oxidation  takes  place  very  slowly,  then  the  total  development 
of  heat  is  the  same  as  in  rapid  oxidation;  still  the  temperature  cannot 
rise  high  enough  to  produce  light.  Often  the  heat  cannot  be  determined 
on  account  of  the  loss  of  the  heat  by  radiation  and  conduction. 

Decay  is  called  the  slow  oxidation  of  organic  bodies  which  takes 
place  with  the  cooperation  of  lower  organisms.  As  the  final  pro- 
ducts are  the  same  in  this  process  as  in  the  combustion  of  organic 
bodies,  we  can  also  consider  this  process  as  a  slow  combustion. 

Respiration  is  also  a  slow  process  of  combustion  when  the  oxygen 
taken  up  by  the  blood  combines  with  a  part  of  the  carbon  of  the  tissues, 
forming  carbon  dioxide,  which  is  expired,  while  the  other  oxidation 
products  are  eliminated  by  the  urine,  etc.  The  body  temperature 
is  produced  by  this  oxidation. 

The  green  plants  take  up  from  the  atmosphere  the  carbon  dioxide 
produced  in  respiration  of  animals,  combustion,  decay,  etc.,  by  means 
of  the  stomata  of  the  leaves,  and  decompose  this  under  the  influence  of 
the  light  into  carbon,  which  serves  to  build  up  its  tissues, and  into  oxygen, 
which  is  eliminated.  The  plants  therefore  perform  a  reduction  process 
which  does  not  occur  in  the  animal  body. 

Combustion,  in  a  chemical  sense,  is  any  chemical  process  accom- 
panied by  the  production  of  light.  As  the  burning  of  a  body  depends 
upon  chemical  processes,  therefore  oxygen  cannot  burn  in  the  air,  as 
there  exists  no  substance  there  with  which  it  can  combine.  Oxygen, 
on  the  contrary,  burns  in  hydrogen,  ammonia,  sulphur  vapors,  etc., 
because  it  combines  with  these  bodies  with  the  development  of  heat 
as  soon  as  the  necessary  temperature,  ignition  temperature  (see 
below)  is  sufficient  to  commence  the  combination. 

As  chlorine  does  not  combine  directly  with  oxygen,  it  does  not  burn 
in  oxygen,  hence  also  not  in  the  air.  Oxygen,  on  the  contrary,  does 
combine  with  hydrogen  and  bums  therein  for  the  same  reason  that 
hydrogen  burns  in  chlorine;  coal-gas  burns  in  the  air,  hence  the  air  (its 
oxygen)  must  burn  in  coal-gas.  It  follows  from  this,  therefore,  that 
burning  or  the  combustibility  of  bodies  are  only  relative  phenomena. 

An  ignited  body  generally  continues  to  burn  because  of  the  heat  set 
free  in  the  combination  of  the  particles  acting  upon  each  other,  heating 
other  particles  to  their  ignition  temperature. 

On  quickly  cooling  (as  by  introducing  a  cold  metal  in  a  small  flame) 
every  flame  may  be  extinguished.     If  a  wire  gauze  is  held  over  a  tube 


110  INORGANIC  CHEMISTRY. 

from  which  coal-gas  is  escaping,  the  gas  may  be  ignited  above  the  wire 
gauze  because  the  metallic  gauze  conducts  away  the  heat  so  well  and 
cools  it  off  so  that  the  gas  between  the  gauze  and  tube  cannot  ignite. 
The  Davy  safety  lamp  used  in  coal-mines  as  a  protection  from  explosion 
of  fire-damp  is  constructed  on  this  principle.  The  oil-lamp  is  entirely 
surrounded  by  wire  gauze,  and  if  such  a  lamp  is  brought  into  a  mixture 
of  explosive  gases  they  ignite  at  the  flame,  but  this  flame  cannot  pass 
through  the  wire  gauze  as  this  cools  the  gases  below  their  ignition  tem- 
perature. 

Ozone  or  Active  Oxygen. 

Oxygen  is  also  known  in  an  allotropic  modification  (p.  80),  which, 
on  account  of  its  powerful  oxidizing  power, is  called  "active  oxygen," 
and  because  of  its  odor  is  called  "ozone"  {o^eiv,  smell). 

Occurrence.  Ozone  occurs  as  traces  in  the  air,  for  instance  after 
a  Ughtning  stroke,  also  in  the  neighborhood  of  "graduation  houses" 
(see  Common  Salt)  and  on  the  seashore,  as  it  always  forms  when  large 
quantities  of  water  quickly  evaporate.  It  is  formed  to  a  less  extent 
also  in  the  oxidation  and  combustion  processes  in  oxygen  or  in  the  air. 
In  these  processes  hydrogen  peroxide  is  nearly  always  produced,  and 
most  of  the  processes,  such  as,  for  instance,  "grass-bleaching"  which 
is  generally  ascribed  to  the  ozone  of  the  air,  is  due  to  the  hydrogen 
peroxide  (which  see). 

Turpentine  and  various  other  ethereal  oils,  also  triethylphosphine, 
absorb  oxygen  with  the  formation  of  peroxides,  which,  like  ozone,  have 
an  energetic  oxidizing  power.  This  property  has  in  the  past  been  as- 
cribed to  ozone. 

Preparation.  1.  By  passing  the  electric  spark  through  oxygen. 
Ozone  may  be  obtained  in  larger  quantities  in  a  special  apparatus, 
whereby  oxygen  is  exposed  to  a  high  tension  electric  current  without 
the  formation  of  sparks  (the  dark  electric  discharge). 

2.  In  the  electrolytic  decomposition  of  water  ozone  is  formed, 
besides  oxygen,  at  the  positive  pole. 

3.  By  passing  oxygen  over  sticks  of  moistened  phosphorus. 

4.  By  introducing  barium  dioxide,  sodium  peroxide,  perman- 
ganates, persulphates,  or  percarbonates  (best  mixed  with  sand)  in  cold 
concentrated  sulphuric  acid. 

5.  By  passing  oxygen  over  manganese  dioxide  (MnOz)  o^  minium 
(Pb304),  which  must  not  be  heated  above  400°.  By  these  methods 
oxygen  containing  a  maximum  of  9  per  cent,  ozone  can  only  be  ob- 
tained.    If  this  is  liquefied  by  being  cooled  with  liquid  air  and  then 


OXYGEN.  Ill 

allowed  to  slowly  evaporate,  the  oxygen  goes  off  at  — 182°,  while  the 
ozone  which  boils  at  — 120°  remains  as  a  deep-blue  liquid. 

Properties.  Colorless,  in  deep  layers  a  bluish  gas  having  a  pecuHar 
odor  similar  to  chlorine,  when  not  too  dilute  causing  an  irritation 
of  the  mucous  membranes,  liquefiable  at  -120°,  forming  a  deep-blue 
liquid  which  readily  explodes  as  it  is  suddenly  transformed  in  oxygen 
gas  with  the  development  of  heat.  It  is  readily  soluble  in  ethereal  and 
fatty  oils  and  only  shghtly  soluble  in  water.  In  the  solution  of  ozone  in 
water  most  of  it  is  converted  into  oxygen  and  hydrogen  peroxide: 
H^0+ 03  =  11^0^4-02.  Although  oxygen  generally  combines  with 
other  bodies  only  at  higher  temperatures,  ozone  has  an  oxidizing 
action  even  at  ordinary  temperatures  (especially  when  moist).  Bright 
silver  is  converted  by  ozone  into  black  silver  peroxide,  white  lead 
hydroxide  into  brown  lead  peroxide,  black  lead  sulphide  (PbS)  into 
white  lead  sulphate  (PbSO^),  etc.  It  destroys  all  vegetable  pigments 
by  oxidation  (use  in  bleaching)  and  oxidizes  all  organic  substances; 
hence  rubber  tubes  must  not  be  used  in  its  preparation. 

If  ozone  is  passed  through  a  glass  tube  heated  above  400°,  it  is 
transformed  into  oxygen  gas,  when  the  volume  increases  one-half; 
the  specific  gravity  of  ozone  is  one-half  greater  than  that  of  oxygen, 
that  is  24  instead  of  16.  Hence  the  molecular  weight  of  ozone  is 
48.  From  this  it  follows  that  a  molecule  of  ozone  contains  3  atoms 
of  oxygen;  hence  2  volumes  of  ozone  yield  3  volumes  of  oxygen. 

In  the  formation  of  ozone  a  considerable  addition  of  energy  takes 
place  in  the  form  of  heat,  electricity,  etc.  This  explains  the  great  chemical 
activity  of  ozone,  as  on  oxidation  with  ozone  32.4  more  calories  are 
set  free  than  with  oxygen  (p.  69).  As  an  endothermic  compound 
liquid  ozone  may  be  suddenly  converted  into  oxygen  gas  with  explosive 
violence. 

Detection.  1.  Paper  moistened  with  potassium  iodide  solution 
and  starch  paste  turns  faintly  or  deep  blue,  depending  upon  the 
quantity  of  ozone. 

Potassium  iodide  is  not  changed  by  oxygen,  but  by  ozone,  on  the 
contrary,  the  potassium  is  oxidized  and  the  iodine  set  free:  03  +  2KI-f- 
H„0=02  4-2KOH  +  I^.  Free  iodine  can  be  detected  by  its  property 
of  turning  starch  deep  blue. 

Precipitated  gum  guaiacum  turns  blue  with  ozone. 

Hydrogen  peroxide  also  gives  the  reaction  with  potassium  iodide 


112  INORGANIC  CHEMISTRY. 

and  starch,  although  only  after  some  time,  while  chlorine,  bromine, 
and  nitric  oxide  gases  also  give  both  reactions. 

2.  In  order  to  differentiate  between  ozone  and  the  above-men- 
tioned bodies  we  make  use  of  paper  moistened  with  an  alcoholic 
solution  of  tetramethyldiamidodiphenylmethane.  In  ozone  this 
paper  turns  violet,  with  nitric  oxide  yellow,  with  chlorine  and  bromine 
blue,  and  does  not  change  with  hydrogen  peroxide. 

a.  Compounds  with  Hydrogen. 
Water,  H^O.     Hydrogen  Peroxide,  HjO,. 

Water,  Hydrogen  Monoxide,  HjO  or  H~0-H.  Occurrence.  Never 
chemically  pure,  but  as  sea-water,  river-water,  spring-water,  in  the 
form  of  clouds,  fog,  rain,  ice,  snow,  hail,  dew,  as  well  as  invisible 
vapor  of  water  in  the  air,  as  water  of  crystallization  in  minerals, 
and  as  a  constituent  of  all  plants  and  animals.  Water  is  also  one 
of  the  products  of  the  combustion  of  all  organic  bodies,  the  pro- 
cesses of  respiration  of  animals,  and  the  union  of  acids  with  bases 
with  the  formation  of  salts  (p.  100),  etc. 

Formation.  1.  By  burning  hydrogen  in  oxygen  or  air  (it  is  the 
oxygen  of  the  air  which  maintains  the  combustion) :  2H-|-0  =H20. 

2.  By  the  union  of  two  volumes  of  hydrogen  and  one  volume  of 
oxygen  (synthesis  of  water) .  This  mixture,  which  may  be  kept  without 
combining,  is  called  "detonating  gas,"  as  both  gases  instantly  unite 
with  a  violent  sound  and  powerful  explosion  when  they  are  ignited 
by  a  burning  body  or  by  spongy  platinum  (p.  105)  or  by  the  electric 
spark;  the  explosion  temperature  of  detonating  gas  lies  between 
500°  and  600°,  that  is,  at  this  temperature  the  reaction  velocity  of 
both  gases  is  accelerated  to  a  remarkable  degree  (p.  73). 

If  the  water  produced  is  converted  into  a  vapor  by  heating,  then 
it  follows  that  from  three  volumes  of  detonating  gas  two  volumes  of 
vapor  of  water  are  produced  (p.  12). 

The  temperature  produced  on  the  union  of  hydrogen  with  oxygen 
is  about  2000°;  the  quantity  of  heat  developed  is  68  large  calories  (p. 
70). 

This  high  temperature  is  made  use  of  in  the  oxyhydrogen  blowpipe 
where  both  gases  first  come  together  at  the  point  of  combustion,  as  other- 
wise the  entire  mixture  would  inflame  and  explode.  Many  highly  re- 
fractory metals,  such  as  platinum,  fuse  in  this  flame;  when  burnt  lime 
(calcium  oxide)  or  zirconia  are  heated  therein  to  a  strong  white  heat  they 


OXYGEN.  113 

emit  an  intense  light,  which  is  used  for  projections,  etc.  (Drummond 
light,  zircon  light). 

3.  If  hydrogen  is  passed  over  heated  metaUic  oxides,  copper 
oxide  (CuO),  iron  oxide  (Fe^Oj),  these  are  reduced  into  metals  with 
the  formation  of  water:  CuO+2H  =Cu+H,0.  Fe^Oj+GH  =2Fe+ 
SHjO.  If  the  copper  oxide  is  weighed  before  and  after  the  experiment, 
and  the  water  formed  also  weighed,  then  the  loss  in  weight  of  the 
copper  oxide  represents  the  quantity  of  oxygen  present  in  the  water 
produced. 

In  explanation  of  the  apparent  contradiction  that  H  yields  H,0 
with  iron  oxide  and  that  iron  with  water  yields  H  see  p.  61. 

Preparation.  In  order  to  prepare  chemically  pure  water  (aqua 
destillata)  on  a  large  scale,  ordinary  water  is  distilled,  i.e.,  we  convert 
the  water  into  vapor  in  a  retort  by  boiling  and  condensing  this  vapor 
again  by  a  cool  surface  (p.  50).  In  this  procedure  all  dissolve(f  salts, 
etc.,  remain  in  the  retort,  as  they  are  not  volatilized  with  the  vapor 
of  water,  while  the  dissolved  gases  (air,  carbon  dioxide,  and  ammonia) 
contained  in  the  water  pass  off  with  the  vapor  produced;  hence  the 
first  portions  of  the  distillate  must  be  discarded. 

Properties.  Pure  water  is  a  tasteless  and  odorless  fluid,  colorless 
in  thin  layers  and  pronouncedly  blue  in  layers  of  six  to  eight  meters; 
only  slightly  compressible,  a  poor  conductor  of  heat  and  electricity. 
It  is  neutral  in  reaction,  i.e.,  it  has  neither  acid  nor  alkahne  proper- 
ties, but  forms  bases  with  basic  oxides,  and  acids  with  acidic  oxides 
(pp.  98  and  99). 

The  alkali  and  alkaline-earth  metals  decompose  water  even  at 
ordinary  temperatures.  The  other  metals  (with  the  exception  of 
lead,  bismuth,  copper,  mercury,  silver,  platinum,  and  gold),  as  well 
as  the  metalloid  carbon,  only  decompose  water  at  higher  temperatures 
with  the  setting  free  of  hydrogen  (p.  104). 

Water  serves  as  the  unit  for  the  determination  of  specific  gravi- 
ties of  solid  and  Uquid  bodies,  as  well  as  the  determination  of  specific 
heat  of  all  bodies,  as  it  possesses  the  greatest  specific  heat,  with  the 
exception  of  hydrogen  (p.  22). 

If  the  electric  current  is  passed  through  acidulated  water,  twice 
as  much  hydrogen  is  set  free  at  the  negative  pole  as  oxygen  at  the 
positive  pole. 

Water  solidifies  at  0°  (ice  formation)  and  expands  at  the  same 


114  INORGANIC  CHEMISTRY, 

time.  One  vol.  water  at  0°  yields  1.07  vols,  ice  at  0°.  Ice  has  there- 
fore a  sp.  gr.  0.93  and  floats  upon  water.  The  ice-flowers  on  the 
windows  and  the  snowflakes  consist  of  regularly  grouped  crystals 
of  the  hexagonal  system. 

The  solidification  of  water  can  be  prevented,  and  ice  can  be  melted, 
by  great  pressure  (p.  35).  Two  pieces  of  ice  pressed  together  may  be 
melted  on  the  surface  pressed,  and  be  made  to  adhere  to  each  other, 
as  the  water  formed  in  melting  immediately  solidifies  again  as  soon 
as  the  pressure  is  relieved.  The  movement  of  glaciers  is  dependent 
upon  this  fact,  because  the  masses  of  ice  resting  upon  the  rocks  by  their 
great  pressure  cause  a  liquefaction  of  the  under  layers  of  ice  and  this 
allows  of  the  movement  of  the  upper  layers. 

The  expansion  of  water  on  freezing  is  of  great  mechanical  importance 
in  nature,  as  the  water  which  has  penetrated  the  rocks  ruptures  them 
on  freezing.  By  repetition  of  this  process  large  masses  of  rocks  are 
gradually  broken  up  into  smaller  pieces  and  then  quickly  "weather." 
Iron  bombs  filled  with  water  and  closed  tightly  are  ruptured  on  cooling 
below  zero. 

Water  has  its  maximum  density  at  4°.  Above  and  below  4°  it 
again  expands;  water  at  9°  has  the  same  density  as  water  at  0°. 
The  weight  of  one  cubic  centimeter  of  water  at  4°  serves  as  the  unit 
of  weight  and  is  called  a  gram. 

The  remarkable  exception  of  water  to  the  laws  of  expansion,  although 
it  is  slight,  is  of  considerable  importance  in  the  economy  of  nature.  If 
the  surface  of  lakes,  ponds,  and  rivers  is  cooled,  then  the  water  on 
the  surface  becomes  heavier  and  sinks,  while  warmer,  lighter  water  comes 
to  the  surface,  until  by  degrees  the  temperature  of  the  total  mass  of 
water  becomes  4°.  If  now  a  further  cooling  takes  place,  then  the  colder 
water  remains  on  the  surface  and  this  only  solidifies  into  ice.  If  the 
density  of  water  increased  to  0°,  then  the  entire  mass  of  water  would 
be  cooled  to  the  freezing-point  and  converted  into  ice;  the  heat  of  the 
summer  would  then  not  be  sufficient  to  melt  this  mass  of  ice. 

Water  which  contains  salts  in  solution  freezes  below  0°  (p.  19)  and 
has  its  maximum  density  at  another  temperature;  thus  with  sea-water 
it  lies  below  0°,  but  this  extensive  mass  is  never  cooled  to  its  freezing- 
point. 

When  water  passes  from  the  solid  to  the  liquid  state,  there  occurs, 
besides  a  diminution  in  volume,  a  disappearance  of  heat  (p.  33) . 

If  one  kilo  of  water  at  0°  is  mixed  with  one  kilo  of  water  at  80°,  we 
obtain  two  kilos  of  water  at  40°;  but  if  we  mix  one  kilo  of  ice  at  0°  and 
one  kilo  of  water  at  80°,  we  then  obtain  two  kilos  of  water  at  0°.  The 
quantity  of  heat  contained  in  the  warm  water  has  disappeared.  The 
heat  of  fusion  of  water  is,  therefore,  80  heat-units  (p.  36). 

At  100°  and  a  pressure  of  760  mm.  (p.  37)  water  is  converted  into 
vapor,  and  at  higher  temperatures  it  decomposes  into  its  elements 


OXYGEN.  115 

(see  dissociation,  p.  71).  Even  at  ordinary  temperatures  water 
and  ice  evaporate.  This  conversion  into  vapor  must  necessarily 
be  accompanied  by  absorption  of  heat;  hence  the  lower  temperature 
of  the  seacoast  depends  upon  the  evaporation  of  the  sea-water.  On 
account  of  the  evaporation  of  water,  the  gases  generated  from  watery 
solutions  are  always  moist  (p.  40).  Vapor  of  water  is  colorless  and 
transparent;  one  volume  of  water  at  100°  yields  1696  volumes  of 
vapor  at  100°;  one  liter  of  vapor  of  water  weighs  at  100°  and 
760  mm.  pressure  0.59  gram.  In  the  passage  of  water  at  100°  into 
steam  at  100°,  as  in  the  passage  of  ice  into  water  at  0°,  a  consid- 
erable quantity  of  heat  is  absorbed  and  set  free  again  on  the  con- 
densation of  the  steam. 

One  kilo  of  vapor  of  water  at  100°  warms  on  conversion  into  water 
at  100°  5.36  kilos  of  water  from  0  to  100°  or  one  kilo  536°.  The  heat 
of  vaporization  of  water,  therefore,  amounts  to  536  heat-units.  Sat- 
urated vapors  do  not  follow  the  law  of  gases  (p.  15).  Their  vapor 
tension  increases  to  a  much  greater  degree  than  their  temperature;  i.e., 
the  vapor  tension  (p.  37)  of  saturated  vapor  of  water  at 
-10°  is     2.1  mm.  100°     is  760  mm. 

0°  "     4.6      "  120.6°  "      2    atmospheres. 

-h20°  "    17.4     "  180.3°  "    10 

40°  "   54.9      "  365.0°  "  194.6 

Above  365°  steam  cannot  be  made  liquid  by  any  pressure;  365°  is 
the  critical  temperature,  194.6  atmospheres  the  critical  pressure  of 
steam   (p.  41). 

Water  of  crystallization  is  that  water  contained  in  many  crystalline 
bodies,  chemically  combined,  which  stands  in  certain  relationship  to 
the  crystalline  form. 

The  quantity  of  water  which  a  salt  at  equal  temperature  takes  up 
in  its  crystallization  is  always  the  same;  at  different  temperatures 
a  salt  may  unite  with  different  quantities  of  water  and  then  also  has 
different  crystalline  forms;  thus  when  magnesium  sulphate  crystallizes 
above  20°  it  forms  tetragonal  crystals,  MgS04  +  4H20,  between  7°  and 
20°  triclinic  crystals,  MgS04  +  5iH20,  below  6°  monoclinic  crystals, 
MgS0,  +  7H,0. 

Water  of  constitution,  or  water  of  hydration,  is  that  portion  of 
the  water  of  crystallization  which  is  firmly  united  and  which,  when 
it  is  given  off,  causes  a  greater  change  in  the  properties  of  the  sub- 
stances to  which  it  belongs  than  the  water  of  crystallization  (see 
Magnesium  Sulphate). 

Efflorescence  is  the  change  which  many  crystals  undergo  when 
exposed  to  dry  air  whereby  they  lose  water  of  crystallization;  they 


116  INORGANIC  CHEMISTRY. 

sometimes  retain  their  form,  but  become  dull  and  non-transparent, 
and  generally  are  converted  into  a  powder. 

Hygroscopic  salts  are  those  which  attract  water  from  the  air, 
so  that  they  often,  when  they  are  very  soluble  therein,  deliquesce. 

Natural  Water.  The  water  occurring  upon  the  earth  is  not  pure, 
but  it  dissolves  the  earth  layers  through  which  it  flows  to  a  more 
or  less  extent.  Besides  this  it  contains  carbon  dioxide  and  air. 
We  differentiate  between  hard  water,  i.e.,  those  which  contain  con- 
siderable calcium  and  magnesium  salts  in  solution,  and  soft  water, 
which  contains  little  solid  matter.  Because  of  the  formation  of 
insoluble  lime  soaps,  hard  water  is  not  suitable  for  washing  (see 
Soaps) ;  peas  and  beans  when  boiled  in  it  do  not  become  tender,  as 
the  proteids  contained  in  them  form  with  the  lime  salts  insoluble, 
hard  compounds. 

1.  Rain-  and  snow-water  (meteoric  water)  is  nearly  pure  water; 
it  contains  only  a  little  air,  carbon  dioxide,  and  ammonium  nitrate. 

2.  Spring-  or  ground- water  is  generally  hard  water;  with  the  aid  of 
the  absorbed  carbon  dioxide  it  dissolves  insoluble  calcium  and  magnesium 
carbonate  forming  acid  carbonates: 

CaC03  +  H20  +  C02=Ca(HC03),. 

Calcium  carbonate.  Acid  calcium  carbonate. 

They  also  generally  contain  calcium  sulphate  (gypsum),  etc.  On  boil- 
ing these  waters,  carbon  dioxide  is  driven  off,  when  the  carbonates  become 
insoluble  again  and  precipitate,  while  the  sulphate  remains  dissolved; 
the  hardness  becomes  less  by  boiling. 

Absolute  or  total  hardne  s  is  the  hardness  of  waters  before  boiling; 
permanent  hardness  is  that  which  remains  after  boiling;  temporary 
hardness,  that  which  disappears  on  boiling.  The  hardness  is  determined 
by  the  addition  of  an  Icoholic  solution  of  soap  whose  strength  has  been 
previously  determined  by  a  calcium  salt.  It  forms  an  insoluble  lime 
soap,  and  a  fine  permanent  lather  is  formed  only  when  all  the  calcium 
and  magnesium  salts  have  been  precipitated.  The  hardness  is  measured 
in  degrees  of  hardness.  A  degree  of  hardness  corresponds  to  one  part 
by  weight  calcium  carbonate  in  1000  parts  by  weight  of  water. 

3.  River  water  is  soft,  although  it  is  often  originally  hard  water; 
this  latter  loses  its  carbon  dioxide  and  hence  the  carbonates  in  the 
act  of  flowing.  Below  cities  river-waters  contain  considerable  organic 
matter. 

4.  Mineral  waters  are  natural  waters  which  contain  either  large 
quantities  of  solid  or  gaseous  bodies  or  have  higlier  temperature  than 
ordinary  water  and  hence  are  used  for  medicinal  purposes. 

We  differentiate  chiefly  between: 

a.  Thermal;   these  have,  as  they  appear  on  the  surface,  a  higher 
temperature  than  the  surroundmg  atmosphere. 


OXYGEN,  117 

b.  Sparkling;    these  contain  especially  considerable  free  carbon 

dioxide;  the  alkaline  ones  besides  this  aodium  carbonate;  the 
saline,  sodium  chloride;  the  alkaline-saline,  carbon  dioxide 
and  sodium  sulphate  or  common  salt. 

c.  Bitter  water  contains  considerable  magnesium  salts. 

d.  Sulphur-water  contains  sulphuretted  hydrogen. 

e.  Salt  water  contains  common  salt,  also  bromine  and  iodine  salts. 
/.   Chalybeate  water  contains  iron  salts. 

5.  Sea-water  differs  from  all  other  waters  by  its  containing  large 
amounts  of  common  salt,  which  amounts  on  an  average  to  2.7  per  cent., 
and  also  contains  bromine,  iodine,  calcium,  magnesium  compounds,  etc., 
so  that  the  quantity  of  solid  bodies  is  about  3.5  per  cent. 

6.  Potable  water.  For  this  purpose  not  only  is  spring-water 
used,  but  also  water  from  rivers  and  lakes.  Such  waters  are  purified 
from  impurities  and  insoluble  substances  by  filtration  by  passing  it 
through  a  receptacle  which  contains  above  sand,  then  gravel,  then  small 
stones  and,  below,  larger  stones.  In  order  to  purify  potable  waters  for 
household  use,  various  filters  of  carbon  or  spongy  iron  are  used  whereby 
the  water  becomes  clearer  and  of  a  better  taste;  still  the  injurious  bodies 
cannot  be  wholly  eliminated  by  any  process  of  filtration.  Good  drinking- 
water  must  be  clear,  colorless,  and  odorless,  must  have  a  fresh  taste 
(due  to  the  carbon  dioxide),  must  not  contain  any  ammonia,  no  nitrous 
acid,  and  only  small  quantities  of  chlorine,  nitrates,  or  sulphates,  organic 
substances,  and  must  not  be  too  hard;  the  evaporated  residue  must 
not  show  under  the  microscope  any  fungi,  infusoria,  etc.  A  drinking- 
water  must  not  necessarily  be  discarded  because  it  contains  the  above 
compounds,  but  because  their  presence  may  possibly  indicate  a  con- 
tamination with  animal  decomposition  products  which  are  not  directly 
detectable. 

Hydrogen  Peroxide,  H^O^  or  H-O-O-H.  Occurrence.  In  very 
small  amounts  in  the  air,  in  rain  and  snow;  it  is  formed  to  a  slight 
extent  in  the  evaporation  of  oil  of  turpentine  (occurrence  in  the  air 
of  pine  forests)  and  other  ethereal  oils,  and  in  the  slow  oxidation 
(action  in  grass-bleaching)  and  combustion  in  the  presence  of  water 
as  well  as  in  the  electrolysis  of  water. 

Preparation.  1.  On  passing  carbon  dioxide  into  water  holding 
barium  dioxide  (Ba02)  '^^  suspension,  or  this  latter  added  to  dilute 
cold  sulphuric  acid  (p.  110): 

Ba02+  H2O+  CO2  =  BaC03+  H2O2; 
Ba02+  H2SO4  =  BaS04+  H2O2. 

The  insoluble  barium  carbonate  or  barium  sulphate  which  precipitates 
is  filtered  off;  the  obtained  dilute  solution  may  be  concentrated  by 
evaporation  not  over  70°  until  it  contains  45  per  cent.  HoOg,  this  solution 
is  then  shaken  with  ether  which  dissolves  the  HgOg,  and  this  latter  solu- 
tion on  distillation  yields  HjOg,  which  is  further  concentrated  in  a  vacuum. 


118  INORGANIC  CHEMISTRY, 

2.  By  dissolving  sodium  peroxide  in  ice-water  (or  dilute  acids) 
we  obtain  a  dilute  solution  of  hydrogen  peroxide  besides  sodium 
hydroxide  (or  the  corresponding  salt) :    Na^Oj^-  2H2O  =  2NaOHH-  HjO,. 

Properties.  Colorless  and  odorless,  bitter,  acid-reacting,  sirupy 
liquid  readily  soluble  in  water  and  which  irritates  the  skin,  and  which 
spontaneously  evaporates  in  the  air.  In  thick  layers  it  forms  a  blue 
liquid  having  a  sp.  gr.  1.5  and  which  is  soluble  in  water  and  which 
when  strongly  cooled  forms  crystals  which  melt  at  —  2°.  If  HjOj  con- 
tains only  traces  of  solid  substances  of  any  kind,  then  it  begins  even 
in  dilute  solutions  to  slowly  decompose  at  20°;  with  greater  heat  it 
effervesces,  and  decomposes  into  water  and  oxygen  often  with  ex- 
plosive violence.  This  decomposition  may  also  be  brought  about 
by  many  finely  divided  metals,  such  as  platinum,  gold,  silver,  or 
manganese  dioxide,  carbon,  etc.,  without  being  changed  themselves 
(Catalysis,  p.  66). 

In  the  dilute  condition  it  is  rather  stable  and  occurs  in  commerce 
as  a  3  per  cent,  by  weight  (or  10  per  cent,  by  volume)  solution  in 
water. 

Hydrogen  peroxide  is  a  powerful  oxidizing  agent,  because  of 
its  ready  decomposition  with  the  production  of  nascent  oxygen;  it 
therefore  bleaches  many  pigments  (hair,  ostrich-feathers),  converts 
dark  hair  into  blonde,  transforms  black  lead  sulphide  into  white 
lead  sulphate  (restoration  of  darkened  oil-paintings),  arsenious  acid 
into  arsenic  acid,  etc.,  precipitates  brown  lead  peroxide  (PbOj)  from 
lead  acetate  solution.  This  lead  peroxide  is  converted  into  yellow 
lead  oxide  (see  below)  by  an  excess  of  H2O2,  and  red  chromium  tri- 
oxide  is  oxidized  to  blue  perchromic  anhydride. 

It  also  acts  as  an  active  reducing  agent  upon  many  unstable 
oxides  and  peroxides,  as  well  as  upon  compounds  of  many  metals  rich 
in  oxygen,  as  the  loosely  combined  oxygen  atoms  in  these  bodies  in 
contact  with  H2O2  form  with  the  loosely  combined  oxygen  atom  a 
free  oxygen  molecule. 

Thus  with  ozone  it  gradually  decomposes  into  water  and  ordinary 
oxygen:    03  +  HA=20g  +  H20. 

Silver  oxide  (AggO)  is  transformed  with  generation  of  oxygen  into 
metallic  silver:    Ag20  +  H202=2Ag  +  H,0  +  02. 

Potassium  permanganate  (KMnO^)  is  converted  in  the  presence  of 
sulphuric  acid  into  colorless  manganous  sulphate  (MnSO^)  whereby 
one-half  of  the  oxygen  is  set  free:  2KMnO,  +  5H202  +  3H2S04=K2SO,+ 
2MnSO,  +  8H20  +  50a. 


SULPHUR.  119 

Calcium  hypochlorite,  Ca(C10)2,  is  converted  into  calcium  chloride, 
when  one-half  of  the  oxygen  is  set  free:  Ca(C10)2  +  2H20o=CaCL  + 
2H2O  +  2O,. 

Detection.  1.  Paper  moistened  with  potassium  iodide  and 
starch,  or  with  tincture  of  guaiacum,  becomes  blue  immediately  in 
contact  with  hydrogen  peroxide.  Indigo  solutions  are  decolorized 
after  the  addition  of  ferrous  sulphate  solution  (ozone  also  gives  these 
reactions  immediately  without  ferrous  sulphate). 

2.  By  the  yellow  color  produced  with  a  solution  of  titanic  acid 
in  dilute  sulphuric  acid,  or  the  orange  color  with  vanadic  acid  in 
dilute  sulphuric  acid. 

3.  If  hydrogen  peroxide  is  added  to  a  red  watery  solution  of 
chromium  trioxide  (or  a  chromate  treated  with  sulphuric  acid),  it 
oxidizes  it  into  the  deep-blue  perchromic  anhydride,  CrjOg,  which  on 
carefully  shaking  with  ether  is  dissolved,  but  which  quickly  decom- 
poses into  chromium  trioxide  and  oxygen. 

2.  Sulphur. 

•      Atomic  weight  32.06  =  S. 

Occurrence.  1.  Free,  sometimes  crystalline,  but  generally  mixed 
with  earthy  matter,  especiatty  in  volcanic  regions,  principally  in 
Sicily  and  Iceland,  having  been  formed  perhaps  by  sulphur  dioxide 
(SO2)  and  sulphuretted  hydrogen  (H2S)  coming  in  contact  with  each 
other:   2H2S-h 80^  =  38 +2H2O. 

2.  In  many  minerals  it  occurs  combined  with  metals,  which  are 
divided  according  to  their  physical  properties  into  blendes,  glance, 
and  pyrites. 

3.  In  the  form  of  sulphuric  acid  salts,  especially  as  calcium  sul- 
phate (gypsum),  which  forms  immense  deposits. 

4.  It  is  found  combined  with  other  elements  to  a  sHght  extent 
in  animals  and  plants,  especially  in  the  protein  bodies,  albuminoids, 
muscles,  epidermis,  in  the  bile,  and  in  many  algse  and  bacteria. 

Preparation.  1.  The  sulphur  is  separated  from  the  matrix  by 
melting  the  same,  in  the  locaUty  where  it  is  found,  and  occurs  in 
commerce  in  irregular  masses  called  crude  sulphur.  The  crude 
sulphur  is  heated  in  iron  vessels,  and  the  sulphur  vapors  formed  are 
condensed  in  chambers  of  masonry  (subhmation,  p.  36). 

If  this  process  takes  place  slowly,  then  the  temperature  of  the 


120  INORGANIC  CHEMISTRY. 

chambers  does  not  rise  above  the  melting-point  of  the  sulphur  and 
the  vaporized  sulphur  precipitates  (Uke  snow  from  watery  vapor)  as 
a  fine  crystalline  powder,  and  occurs  in  commerce  as  flowers  of  sulphur. 
If  the  sublimation  is  rapid,  or  if  the  sulphur  vapors  are  passed  into 
the  chamber  for  a  long  time,  then  the  temperature  of  the  chamber  be- 
comes so  high  that  the  condensed  sulphur  melts;  it  is  then  poured 
into  wooden  moulds,  forming  the  rolled  sulphur  or  rolled  brimstone 
of  commerce  which  has  a  crystalline  fracture. 

2., In  the  Leblanc  soda  manufacture  (which  see)  about  30  per  cent, 
calcium  sulphide,  CaS,  is  obtained  as  a  by-product  from  which  the 
sulphur  can  be  obtained  (see  Soda). 

3  Sulphur  may  also  be  obtained  by  heating  iron  pyrites  in  the 
absence  of  air:    FeS2=FeS  +  S. 

Properties.  A  yellow,  brittle,  crystalline,  tasteless  and  odorless 
solid  which  on  rubbing  becomes  electrified,  is  insoluble  in  water, 
but  somewhat  soluble  in  alcohol  and  ether,  and  readily  soluble  in  tur- 
pentine, benzol,  carbon  disulphide,  and  rather  soluble  in  fatty  and 
ethereal  oils. 

It  melts  at  114°,  forming  a  pale-yellow,  m6bile  liquid  which  at 
160°  turns  brown  and  less  fluid;  at  230°  it  becomes  dark  brown  and 
very  viscous,  so  that  the  vessel  may  be  turned  upside  down  without 
the  liquid  flowing  out.  On  heating  still  higher  it  becomes  again 
hquid,  but  not  light  in  color,  and  at  448°  it  begins  to  boil  and  is  con- 
verted into  a  brownish-yellow  vapor. 

When  sulphur  is  heated  in  the  air  or  in  oxygen  to  260°  it  inflames 
and  burns  with  a  bluish  flame  with  the  formation  of  sulphur  dioxide 
(SO2),  an  irritating  gas.  Sulphur  has,  next  to  oxygen,  the  greatest 
affinity  for  other  elements,  with  the  exception  of  fluorine,  argon, 
helium,  neon,  krypton,  and  xenon,  and  unites  often  in  several  pro- 
portions with  the  elements.  The  compounds  of  sulphur  correspond 
nearly  in  composition  to  those  of  oxygen,  and  are  called  sulphides  or 
polysulphides  when  they  contain  more  than  one  atom  of  sulphur 
in  the  molecule. 

Sublimed  sulphur  always  contains  some  sulphurous  or  sulphuric 
acid,  often  also  arsenic  sulphide,  which  can  be  removed  by  treating  it 
with  a  dilute  solution  of  ammonia  and  then  washing  with  water. 

If  sulphur  hich  has  been  melted  at  114°  is  allowed  to  cool  slowly, 
thin  pliable  monocUnic  prisms  having  a  specific  gravity  of  1.96  and  melting 
at  120°  are  obtained.     These  crystals  on  shaking,  or  on  being  kept  for 


SULPHUR.  121 

some  time,  become  non-transparent  and  brittle  and  are  transformed 
into  rhombic  octahedra. 

Natural  sulphur  crystallizes  always  in  rhombic  octahedra  having  a 
specific  gravity  of  2.07;  from  superheated  sulphur  (p.  35)  rhombic 
octahedra,  which  melt  at  90°,  may  separate  out.  Hence  sulphur  is  dimor- 
phous; both  forms  separate  out  always  as  rhombic  octahedra  from  its 
solution  in  carbon  disulphide  after  the  evaporation  of  the  same 

Detection.  1.  When  sulphur  is  heated  it  melts  and  volatilizes; 
it  burns  with  a  blue  flame,  forming  sulphur  dioxide,  which  may  be 
detected  by  its  odor. 

2.  All  sulphur  compounds  when  heated  with  soda  upon  char- 
coal yield  sodium  sulphide,  which  can  be  detected  by  the  generation 
of  sulphuretted  hydrogen  when  the  fused  mass  is  treated  with  acids, 
or  when  the  mass  is  moistened  with  water  and  placed  upon  a  silver 
coin,  when  a  dark-brown  spot  of  silver  sulphide  will  be  obtained. 

See  also  Part  III,  "Elementary  Analysis." 

Plastic  Sulphur.  If  sulphur  which  has  been  heated  above  230°  is 
slowly  poured  into  cold  water,  we  obtain  an  amorphous,  brownish- 
yellow,  transparent,  elastic  mass,  which  is  called  plastic  sulphur, 
having  a  specific  gravity  of  1.95  and  which  gradually  solidifies,  being 
converted  into  rhombic  sulphur.  Plastic  sulphur  is  a  mixture  of 
the  two  amorphous  modifications  of  sulphur,  of  which  the  brown 
one  is  soluble  in  carbon  disulphide,  while  the  other  remains  undissolved 
as  a  yellow  amorphous  powder. 

Flowers  of  sulphur  (p.  120)  is  a  mixture  of  the  insoluble  amor- 
phous sulphur  and  of  rhombic  sulphur. 

Milk  of  sulphur,  a  third  modification,  is  produced  when  sulphur 
is  set  free  from  aqueous  solutions  of  metallic  polysulphides  by  acids: 
K2S5+2HC1  =  2KCH-H2S+4S.  (If,  on  the  contrary,  a  solution  of  a 
metaUic  polysulphide  is  added  to  an  excess  of  acid,  hydrogen  persul- 
phide  separates,  see  p.  124.)  This  modification  is  soluble  in  carbon 
disulphide  and  forms  a  fine,  dirty-white  powder  which  is  gradually 
transformed  into  rhombic  sulphur. 

The  existence  of  different  allotropic  modifications  of  sulphur  (p.  80) 
can  be  explained  by  the  fact  that  the  molecule  of  these  different  modi- 
fications consists  of  a  different  number  of  atoms  (see  Dissociation,  p.  72). 


122  INORGANIC  CHEMISTRY. 

a.    Compounds  with  Hydrogen. 
Hydrogen  Sulphide,  HgS.     Hydrogen  Persulphide,  HjSj. 

Hydrogen  Sulphide,  Sulphuretted  Hydrogen,  HgS.  Occurrence. 
To  a  slight  extent  in  the  gases  of  volcanoes  and  in  sulphur-waters; 
also  where  organic  bodies  containing  sulphur  undergo  putrefaction,  as 
well  as  in  the  gases  of  the  intestine  of  carnivorous  animals  and  in 
pathological  urine. 

Formation.  1.  By  the  action  of  nascent  H  upon  sulphur  diox- 
ide:   SO,+  6H=2H,0+H,S. 

2.  By  heating  sulphur  and  many  metallic  sulphides  in  a  current 
of  hydrogen :   Ag,S+  2H  =  2Ag+  H,S. 

Preparation.  By  the  action  of  dilute  hydrochloric  or  sulphuric 
acid  upon  metallic  sulphides,  especially  ferrous  or  antimony  sulphide: 

FeS+  H2SO4  =  FeS04+  H^S; 
Sh,Ss+  6HC1  =  2SbCl3+  SH^S. 

Properties.  Colorless,  poisonous,  gas  having  a  disagreeable  odor 
similar  to  rotten  eggs  (which  contain  the  same),  having  a  specific 
gravity  of  1.18;  inflames  and  burns  with  a  blue  flame  into  sulphur 
dioxide  and  water:  H2S+30  =  H20+S02;  if  the  supply  of  oxygen 
is  diminished,  then  sulphur  is  set  free:  2H2S+4O  =2H20 +80^+8. 

It  can  be  liquefied  at  —74°,  forming  a  colorless  liquid  which 
solidifies  in  crystals  at  —85°.  One  volume  of  water  at  0°  dissolves 
3.7  volumes  of  the  gas;  this  solution  reddens  litmus,  and  is  oxidized 
into  water  with  the  setting  free  of  sulphur  by  many  compounds  con- 
taining oxygen,  such  as  chromic  acid,  nitric  acid,  etc.,  as  well  as  by 
the  oxygen  of  the  air:  H2S+0  =  H20+S. 

Stronger  oxidizing  agents,  such  as  fuming  nitric  acid,  lead  peroxide, 
may  ignite  the  gas,  and  when  mixed  with  oxygen  it  explodes  when  a 
light  is  applied.  Sulphuretted  hydrogen  is,  therefore,  a  powerful 
reducing  agent.  Chlorine,  bromine,  and  iodine  decompose  it  with  the 
setting  free  of  sulphur,  they  combining  with  the  hydrogen:  H2S4-2C1  = 
2HCH-S.  Sulphur  dioxide  acts  in  a  similar  manner:  S02+2H2S  = 
2H,0+3S. 

Most  metals  decompose  sulphuretted  hydrogen  on  heating  them 
together  with  the  formation  of  sulphides  (p.  120),  and  hydrogen  is  set 
free  at  the  same  time.     The  metalhc  oxides  have  a  similar  action  and 


SULPHUR.  123 

form  water.  With  certain  of  these  bodies  the  combination  takes 
place  even  in  the  cold;  hence  silver,  copper,  white  lead,  etc.,  turn 
black  even  in  the  air,  as  this  often  contains  small  amounts  of  sul- 
phuretted hydrogen:   2Ag-f H2S=Ag2S+2H. 

Sulphuretted  hydrogen  behaves  like  the  analogous  hydrogen 
acids  of  the  chlorine  group,  and  the  sulphides  may  be  considered 
as  salts  of  hydrosulphuric  acid. 

The  acid  sulphides,  such  as  NaHS,  have  a  neutral  reaction  in  aqueous 
solution  because  the  HS'  ion  is  only  slightly  dissociated,  so  that  the 
acid  reaction  of  the  H'  ions  is  not  sensible,  while  the  neutral  sulphides, 
on  the  contrary,  have  an  alkaline  reaction  because  the  hydroxyl  ions 
OH'  are  formed  by  hydrolytic  dissociation  (p.  86):  NaoS  +  HOHs: 
Na-+HS'+Na-+OH'. 

On  account  of  its  behavior  to  metals  and  their  compounds,  HjS, 
as  well  as  its  aqueous  solution,  is  an  important  reagent  and  pre- 
cipitant for  the  metals. 

The  sulphides  obtained  with  H2S  may  be  divided  into  the  following 
three  groups: 

1.  Sulphides  which  are  not  acted  upon  by  dilute  acids. 

2.  Sulphides  which  are  insoluble  in  water,  but  are  decomposed  by 
acids. 

3.  Sulphides  which  are  soluble  in  water. 

Because  of  this  behavior  sulphuretted  hydrogen  can  be  used  in 
chemical  analysis  in  separating  the  metals  into  these  three  groups  by 
passing  sulphuretted  hydrogen  into  the  solution  of  the  metallic  salt 
to  be  tested  which  has  previously  been  acidified  with  an  acid,  when  the 
metals  of  the  first  group  precipitate;  if  the  precipitated  sulphides  are 
removed  by  filtration  and  the  filtrate  neutralized,  then  the  sulphides 
of  the  second  group  precipitate,  while  those  of  the  third  group  remain 
in  solution. 

Many  sulphides  have  a  characteristic  color,  so  that  HgS  is  not  only  a 
means  of  separating  the  metals  into  three  groups,  but  it  may  also  serve 
as  a  means  of  identification  for  certain  of  the  metals.  Thus  from  anti- 
mony solutions  it  precipitates  orange-red  antimony  sulphide,  from  arsenic 
solutions  yellow  arsenic  sulphide,  from  zinc  solutions  white  zinc  sulphide, 
from  manganese  solutions  flesh-colored  manganous  sulphide,  from  iron 
solutions  black  ferrous  sulphide:  FeS04  +  H2S=FeS  +  H2S04;  but  as 
the  manganous,  ferrous,  and  zinc  sulphides  are  soluble  in  acids,  the  sul- 
phuretted hydrogen  only  precipitates  these  when  the  acid  set  free  is 
neutralized. 

Detection.  1.  Sulphides  generate  sulphuretted  hydrogen  gas 
when  treated  with  acids.  This  gas  may  be  detected  by  its  odor 
and  by  its  blackening  paper  moistened  with  a  lead  salt  solution. 

2.  Sodium  nitroprusside  gives  a  violet  color  with  sulphide  solu- 
tions. 


124  INORGANIC  CHEMISTRY. 

Hydrogen  persulphide,  U^Q^^r  HS-SH,is  obtained  when  a  watery 
solution  of  a  polysulphide,  for  instance,  of  calcium  disulphide  (CaSj), 
is  added  drop  by  drop  to  an  excess  of  dilute  hydrochloric  acid: 
CaS2+2HCl  =  CaCl2+H2S2  (p.  121).  It  forms  a  thick,  yellow  liquid 
with  a  disagreeable  odor,  which  bleaches  organic  pigments,  and 
which  gradually  decomposes,  but  quicker  on  heating,  into  H2S+S. 
Hydrogen  persulphide  probably  has  the  formula  H2S5,  which  body 
is  formed  first  from  the  unstable  hydrogen  polysulphide  produced: 
4H2S,  =  3H2S5+  HjS;    4H2S2  =  H2S5+  3H2S;   4H2S3  =  2H2S5+  2H2S. 

b.  Compounds  with  Oxygen. 
—  Hyposulphurous  acid,  HgSgO^. 


Sulphur  dioxide, 

SO2. 

Sulphurous  acid, 
Pyrosulphurous  acid, 

H2SO3. 
H,S,0, 

Sulphur  trioxide, 

SO3. 

j  Sulphuric  acid, 

\  Pyrosulphuric  acid, 

H3SO,. 
HAO,. 

Sulphur  sesquioxide 

S2O3 

— 

Sulphur  heptoxide, 

SP: 

Persulphuric  acid. 

HAOs. 

— 

Oxysulphuric  acid, 

H2SO5. 

— 

Thiosulphuric  acid. 

HAO3. 

— 

Dithionic  acid. 

H^S^Oe. 

— 

Trithionic  acid. 

H^30„. 

— 

Tetrathionic  acid, 

H,S,Oe. 

— 

Pentathionic  acid. 

HAOe. 

Of  these  acids  only  sulphuric  acid  and  pyrosulphuric  acid  can  be 

Srepared ;  the  other  acids  are  only  known  in  aqueous  solution  or  as  salts. 
►f  the  last  six  acids  the  anhydrides  are  not  known.  The  last  four 
acids  form  the  group  of  acids  called  polythionic  acids  (ttoAi)?,  many, 
^eiov,  sulphur).  Sulphuric  acid,  pyro-  and  oxysulphuric  acids,  as  well 
as  their  salts,  are  precipitated  by  barium  salt  solutions  from  their  acid 
solutions. 

Sulphur  Dioxide,  Sulphurous  Anhydride,  SO2.  Occurrence.  In 
the  gases  of  volcanoes. 

Preparation.  1.  On  a  large  scale  by  burning  sulphur  or  by 
roasting  sulphides,  or  from  the  residue  from  the  Leblanc  soda  manu- 
facture (p.  127). 

2.  Ordinarily  by  heating  copper,  carbon,  or  sulphur  with  con- 
centrated sulphuric  acid: 

2H2SO,+  C   =2H20+C02+2S02; 
2H2SO4+  Cu  =  2H2O+  CUSO4+  SOaJ . 
2H2SO4+S    =2H20+2S02. 


SULPHUR.  125 

3.  In  smaller  quantities  by  the  action  of  sulphuric  acid  upon 
calcium  sulphite  or  upon  sodium  bisulphite: 

CaS03+  H2SO4  =  CaS04+  H2O+  SO2; 
2NaHS03+  H2SO4  =  Na^SO^^-  2H2O+  2SO2. 

4.  By  heating  sulphur  with  metaUic  oxides: 

2CuO+3S  =2CuS+S02;  Mn02+2S  ^MnS+SO^. 

Properties.  Colorless,  irritating,  neutral  gas,  2.21  times  heavier 
than  air,  Uquefiable  at  -10°  (p.  41)  to  a  colorless  liquid  which  solidifies 
in  white  flakes  at  —  76°.  It  is  not  combustible  and  does  not  support 
the  combustion  of  carbon  compounds,  but  many  metalHc  oxides 
combine  when  heated  in  it  with  the  production  of  flame;  thus  brown 
lead  dioxide  is  converted  into  white  lead  sulphate : 

Pb02+S02=PbS04. 

It  bleaches  many  organic  pigments  in  the  presence  of  water;  this 
does  not  depend  upon  oxidation  hke  the  chlorine  bleaching,  but 
depends  upon  the  union  of  the  sulphurous  acid,  HjSOg,  produced 
with  the  pigments.  These  compounds  are  unstable  and  on  warming 
or  with  bases  and  acids,  etc.,  decompose  under  certain  circumstances 
so  that  the  color  appears  again  (use  of  burning  sulphur  for  bleaching; 
animal  fibres  are  not  decolorized  so  completely  with  chlorine  as  with 
SO2).  It  has  rather  great  affinity  for  oxygen,  hence  it  removes  the 
same  from  many  oxygen  compounds,  such  as  chromic  acid,  iodic 
acid  (see  below),  etc.  It  is,  therefore,  a  powerful  reducing  agent;  it 
only  unites  directly  with  free  oxygen  in  the  presence  of  spongy 
platinum,  etc.  (p.  126);  it  is  converted  into  sulphuric  acid  by  the 
halogens  when  in  watery  solution:  S02+2H20+2I=H2S04+2HI. 
It  is,  therefore,  employed  to  remove  the  excess  of  chlorine  used 
in  bleaching  certain  materials  which  would  otherwise  destroy  the 
fabric.  On  the  other  hand,  strong  reducing  agents  (H,  HjS) 
reduce  it  again  to  sulphur  (p.  122).  It  prevents  putrefaction 
and  fermentation  and  serves  as  a  preservative  (sulphuring  of  wine- 
barrels,  etc.).  Water  dissolves  50  times  its  volume  of  this  gas 
at  15°. 

Detection.    If  a  piece  of  paper  moistened  with  starch  and  iodic 


126  INORGANIC  CHEMISTRY, 

acid  (or  potassium  iodate)  is  suspended  in  sulphur  dioxide  gas,  it  turns 
blue,  due  to  the  setting  free  of  iodine  (p.  Ill) : 

2HIO3+  5SO2+  4H2O  =  21+  5H2SO4. 

An  excess  of  SO^  decdlorizes  this  paper  (process  above). 

Sulphurous  Acid,  H2SO3  or  HO-SO~OH.  The  aqueous  solution 
of  sulphur  dioxide  has  an  acid  reaction  and  may  be  considered  as 
dissolved  sulphurous  acid,  although  this  has  never  been  isolated, 
as  it  decomposes  again  into  water  and  sulphur  dioxide  on  evaporation, 
'if^this  solution  is  cooled  to  —5°,  then  crystals  having  the  formula 
H2SO3+I4H2O  separate  out;  on  standing  in  the  air  the  solution  is 
converted  into  sulphuric  acid. 

Sulphites.  If  the  aqueous  solution  of  sulphur  dioxide  is  neutral- 
ized with  bases  and  then  evaporated,  we  obtain  the  sulphites: 
2NaOH+H2S03  =  Na2S03+2H20;  these  are  converted  in  aqueous 
solution  into  sulphates  on  standing  in  the  air.  Acids  readily  decom- 
pose the  sulphites,  setting  free  sulphurous  acid,  which  decomposes 
further  into  water  and  sulphur  dioxide:  NaS03+2HCl=2NaCl+ 
H2O+SO2.  In  regard  to  the  probable  existence  of  sulphites  of 
various  constitution,  see  Taurin. 

Detection.  SOj  is  set  free  from  the  sulphites  by  the  addition  of 
an  acid.     This  can  be  detected  as  described  above. 

Sulphur  Trioxide,  Sulphuric  Anhydride,  SO3.  Preparation.  1.  On 
a  large  scale  by  the  so-called  contact  method,  where  dry,  arsenic- 
free  sulphur  dioxide  and  oxygen  (or  air)  is  passed  over  heated,  finely 
divided  platinum  on  asbestus  (platinized  asbestus),  which  acts  as  the 
contact  substance  (p.  125).  The  temperature  must  not  rise  above 
450°,  as  at  higher  temperatures  the  SO3  formed  is  again  decomposed 
into  SO2+  O  in  the  presence  of  the  platinum. 

2.  On  heating  ferrous  sulphate  (p.  130)  or  sodium  pyrosulphate 
(p.  130):   Na2S20;=Na2S04+S03. 

3.  On  the  distillation  of  fuming  sulphuric  acid  (p.  129). 

The  vapors  produced  in  these  three  methods  are  condensed  by 
cold. 

Properties.  Long,  colorless,  neutral,  caustic  prisms  which  blacken 
organic  substances,  melt  at  14°,  and  which  in  the  presence  of  traces 
of  water  are  converted  into  silky,  asbestus-like  needles  of  pyrosul- 
phuric  anhydride,  SjOj,  which  melt  at  50°,  which  are  less  caustic. 


SULPHUR.  127 

etc.,  and  which  form  the  commercial  product.  They  fume  strongly  in 
the  air,  as  they  are  somewhat  volatile  even  at  ordinary  temperatures, 
and  the  vapor  absorbs  water  from  the  air,  forming  sulphuric  acid, 
which  immediately  condenses  into  small  visible  globules.  It  dis- 
solves in  water  with  a  liissing  sound  with  the  production  of  great 
heat,  forming  sulphuric  acid:    S03+H20=H2S04. 

Sulphuric  Acid,  Oil  of  Vitriol,  H^SO^  or  HO-SO^-OH.  Occur- 
rence. Free  to  very  trivial  extent  in  certain  volcanic  springs 
of  America,  and  in  the  air  in  regions  where  large  quantities  of  coal 
are  burnt.  It  occurs  in  large  quantities  combined  as  sulphates,  of 
which  calcium  sulphate,  CaS04,  gypsum,  forms  entire  geological 
strata,  also  as  barium  sulphate,  BaS04,  and  strontium  sulphate, 
SrSOi.  Animals  and  plant  fluids  also  contain  sulphates,  generally 
of  the  alkali  metals. 

Preparation.  1.  In  small  quantities  by  boiling  sulphur  with 
concentrated  nitric  acid :  S+  2HNO3  =  H2SO4+  2N0. 

2.  By  dissolving  sulphur  trioxide  prepared  by  the  contact  method 
in  water.  Oh  account  of  the  ready  and  less  dangerous  transporta- 
tion of  SO3  it  is  economical  to  prepare  sulphuric  acid  by  dissolving 
SO3  in  water  at  the  locality  where  it  is  to  be  used.  For  these  reasons 
the  following  method  of  preparation  is  used  to  a  less  extent  at  the 
present  day. 

3.  By  the  oxidation  of  sulphur  dioxide  by  nitric  acid  or  its  decom- 
position products  in  the  presence  of  water  and  air  in  chambers  lined 
with  lead  plates  (lead  chambers).  An  aqueous  solution  of  sulphur 
dioxide  is  only  slowly  oxidized  into  sulphuric  acid  by  the  oxygen  of 
the  air  (p.  126) ;  but  this  may  be  made  to  take  place  more  quickly 
in  the  presence  of  contact  substances  or  when  compounds  which 
readily  give  off  oxygen  are  present;  such  compounds  are  nitric  acid 
(HNO3)  and  nitrogen  dioxide  (NO2),  which  are  reduced  to  nitric  oxide 
(NO)  thereby. 

The  sulphur  dioxide  is  prepared  by  roasting  the  residues  from  the 
Leblanc  soda  manufacture,  the  iron  residues  used  in  the  purification 
of  illuminating-gas  (see  Potassium  Ferrocyanide),  or  by  roasting  metallic 
sulphides  and  especially  iron  pyrites  (FeSg),  copper  pyrites  (CuS  +  FeS), 
lead  pyrites  (PbS),  zinc  blende  (ZnS),  which  are  converted  into  oxides 
thus:    2FeS2  +  110=FeA  +  4S02. 

The  nitric  acid  is  generated  from  2NaN03  +  H2S04  by  introducing 
this  mixture  into  crucibles  placed  in  the  roasting-ovens  and  the  vapors 


128  INORGANIC  CHEMISTRY. 

introduced  with  the  sulphur  dioxide  through  the  Glover  towers  into  the 
lead  chambers,  in  which,  at  the  same  time,  steam  and  air  are  conducted. 

The  acid  (chamber  acid)  which  collects  contains  about  60  per 
cent,  sulphuric  acid  and  is  concentrated  by  heating  first  in  lead  pans 
and  contains  then  about  80  per  cent,  sulphuric  acid  (pan  acid).  As 
a  stronger  acid  than  this  attacks  lead  on  boiling,  it  is  further  concen- 
trated in  glass  or  platinum  vessels  until  it  contains  about  92  to  94 
per  cent,  sulphuric  acid  (crude  sulphuric  acid) .  The  following  trans- 
formation takes  place  in  the  lead  chambers :  ^ 

a.  3SO2+  2HNO3+  2H2O  =  3H,S04+  2N0. 

b.  A  part  of  the  nitric  oxide  (NO)  produced  is  transformed  by 
the  oxygen  of  the  air  and  by  the  steam  into  nitric  acid,  which  again 
can  oxidize  a  new  portion  of  sulphur  dioxide  into  sulphuric  acid: 

2N0+  30+  HP  =  2HNO3. 

c.  A  part  of  the  nitric  oxide  combines  with  the  atmospheric 
oxygen,  forming  nitrogen  dioxide  (NO2),  which,  in  the  presence  of 
steam,  oxidizes  the  sulphur  dioxide  into  sulphuric  acid: 

S0,4-  H2O+  NO2  =  H,S04+  NO. 

The  regenerated  nitric  oxide  again  undergoes  the  same  transforma- 
tion as  described  in  b  and  c. 

Besides  these,  probably  other  processes  may  take  place,  especially 
the  following: 

a.  First  nitrosylsulphuric  acid  (nitrosulphonic  acid)  is  produced; 
S02  +  HN03=HO-S02-0(NO). 

b.  Nitrosylsulphuric  acid  is  only  stable  in  certain  concentrations  and 
temperatures  and  is,  therefore,  in  contact  with  sufficient  water  or  dilute 
sulphuric  acid  immediately  decomposed: 

2H0-S0,-0(N0)  +  HgO^  2HO-SO2-OH  +  NO +N0,. 

c.  Then  nitrosylsulphuric  acid  is  again  formed,  etc.: 

2S02+NO  +  N02+H20-f20=2HO-S02-0(NO). 

If  it  were  possible  in  this  process  to  prevent  any  loss,  then  a  small 
quantity  of  nitric  acid  could  produce  an  unlimited  quantity  of  sulphuric 
acid;  but  as  with  one  volume  of  oxygen  four  volumes  of  nitrogen  are 
introduced  (by  the  use  of  air  instead  of  oxygen),  the  gases  are  diluted 
too  much  and  must  be  continuously  resupplied  from  without.  The 
nitrogen  on  being  removed  from  the  chambers  takes  a  part  of  the  oxides 
of  nitrogen  with  it,  which  can  be  regained  again  by  passing  the  gases 
(before  they  come  to  the  chimney  which  maintains  the  draft)  through 
Gay-Lussac  towers.     In  these  towers,  which  are  filled  with  coke,  strong 


r 


SULPHUR.  129 

sulphuric  acid  is  allowed  to  trickle,  and  this  dissolves  all  the  oxides 
of  nitrogen.  This  solution,  the  so-called  nitroso  acid,  is  allowed  to  trickle 
through  the  Glover  tower,  which  is  also  filled  with  coke  and  is  placed  at 
the  other  end  of  the  lead  chambers.  The  sulphur  dioxide  entering  re- 
moves from  the  nitroso  acid  the  oxides  of  nitrogen  and  carries  them  into 
the  lead  chamber. 

If  in  these  processes  water  is  absent,  then  nitrosylsulphuric  acid 
deposits  in  the  lead  chambers  as  white  crystals,  so-called  lead-chamber 
crystals,  which  decompose  in  the  piesence  oi  water  (see  p.  128,  6). 

Properties.  Sulphuric  acid  is  a  thick,  colorless  liquid,  which  with 
dust,  etc.,  readily  darkens;  it  has  a  great  affinity  for  water,  hence  it 
is  used  in  drying  gases  and  for  filling  desiccators.  When  mixed 
with  water  considerable  heat  is  evolved;  hence  on  mixing  these 
the  sulphuric  acid  should  always  be  added  to  the  water,  and  indeed 
in  a  thin  stream,  otherwise  a  violent  explosion  may  take  place.  On 
account  of  its  great  affinity  for  water,  sulphuric  acid  removes  oxygen 
and  hydrogen  in  the  proportion  of  water  from  many  organic  com- 
pounds; the  preparation  of  carbon  monoxide  from  oxalic  acid,  of 
ethylene  from  alcohol,  the  carbonization  action  of  sulphuric  acid 
upon  sugar,  wood,  paper,  etc.,  depends  upon  this  action.  If  the 
vapor  of  sulphuric  acid  is  passed  over  heated  bricks,  it  decomposes 
into  SO2+H2O+O. 

Sulphuric  acid  is  a  strong  bibasic  acid,  forms,  therefore,  acid  and 
neutral  salts,  and  expels  most  other  acids  from  their  salts  on  heating. 

Most  metals  dissolve  in  cold,  dilute  sulphuric  acid  with  the  genera- 
tion of  hydrogen,  or  in  hot,  concentrated  sulphuric  acid  with  the  gen- 
eration of  sulphur  dioxide,  forming  sulphates.  Lead,  platinum,  gold, 
and  certain  rare  metals  are  not  attacked  by  sulphuric  acid. 

Crude  or  English  sulphuric  acid  (oil  of  vitriol)  contains  91  to  94  per 
cent,  sulphuric  acid,  has  a  specific  gravity  of  1.830  to  1.837,  contains  con- 
taminations such  as  lead,  oxides  of  nitrogen,  and  often  arsenic. 

Pure  sulphuric  acid  is  obtained  by  distilUng  crude  sulphuric  acid; 
hereby  first  a  dilute  sulphuric  acid  distils  over  until  the  boiling-point 
rises  to  330°,  when  a  pure  sulphuric  acid  distils  over  which  contains 
only  1.5  per  cent,  water  and  has  a  specific  gravity  of  1.836  to  1.84  (p.  53). 

"Anhydrous  sulphuric  acid  is  obtained  by  cooHng  pure  sulphuric  acid 
to  —  25°  or  by  adding  crystals  of  sulphuric  anhydride  to  strongly  cooled  sul- 
phuric acid.  It  forms  colorless  crystals  having  a  specific  gravity  of  1.837 
which  melt  at  10°;  they  cannot  be  distilled  without  decomposition. 
On  heating,  they  first  evolve  sulphur  trioxide,  and  at  330°  a  sulphuric 
acid  of  98.5  per  cent   distils  over  (Dissociation,  p   71). 

Fuming  sulphuric  add,  or  Nordhausen  oil  of  vitriol,  is  now  pre- 
pared by  dissolving  sulphur  trioxide  obtained  by  the  contact  method 


130  INORGANIC  CHEMISTRY, 

in  crude  sulphuric  acid.    It  used  to  be  obtained  by  heating  roasted, 
ferrous  sulphate. 

On  roasting  ferrous  sulphate  it  is  transformed  into  ferric  oxide  and 
ferric  sulphate,  6FeSO<  +  30=2Fe2(SO4)3  +  Fe2O3,  which  decomposes  at 
a  red  heat  according  to  the  following  equation:  Fe2(SOj3=Fe203+  SSOg; 
the  sulphur  trioxide  which  distils  off  is  collected  in  small  quantities 
of  water  or  sulphuric  acid;  the  iron  oxide  (FcgOa)  which  remains  in  the 
retort  is  called  colcothar. 

It  forms  a  thick  liquid  which  fumes  in  the  air  and  has  a  specific 
gravity  of  1.85  to  1.90  and  may  be  considered  as  a  compound  of  sul- 
phuric anhydride  with  sulphuric  acid  as  on  cooling  the  following  acid 
separates: 

Pyro-  or  disulphuric  acid,  H^SjOy,  forms  colorless  crystals  which 
melt  at  35°  and  is  prepared  commercially  by  dissolving  SO3  into  con- 
centrated sulphuric  acid.  On  heating  it  decomposes  into  H2SO4 
and  SO3  (p.  126) ;  its  salts  are  obtained  by  heating  the  primary  sul- 
phates: 2KHS04=H20+K2S207,  which  further  decomposes  on 
heating  into  K2SO4+SO3. 

Sulphates  are  obtained  either  by  dissolving  the  respective  metals 
in  sulphuric  acid  or  by  neutralizing  a  base  with  sulphuric  acid,  also 
by  oxidizing  the  metallic  sulphides  or  metallic  sulphites  at  a  gentle 
heat  in  the  air.  In  this  wise  copper  and  iron  sulphates  are  prepared 
on  a  large  scale:  CuS+40  =CuS04. 

The  sulphates  of  the  alkalies,  of  the  alkahne  earths,  and  of  lead 
are  not  changed  on  heating  to  a  high  degree;  the  other  sulphates 
dcompose  into  sulphur  dioxide  or  sulphur  trioxide  and  metal  (or 
metallic  oxides)  and  oxygen. 

Detection.  Sulphuric  acid  and  the  soluble  sulphates  give  white 
precipitates  of  barium  sulphate  (BaS04)  or  lead  sulphate  (PbSOi) 
with  barium  or  lead  salt  solutions.  These  precipitates  are  insoluble 
in  acids. 

On  fusion  with  sodium  carbonate  the  insoluble  sulphates  are 
converted  into  soluble  sodium  sulphate  in  which  the  sulphuric  acid 
can  be  detected  as  above  described. 

Sulphur  sesquioxide,  SgOg,  is  produced  by  introducing  powdered 
sulphur  into  sulphur  trioxide,  and  forms  bluish-green  crystals:  S-f-S03= 
SaO,;   with  water  it  decomposes  into  H2SO4  +  S. 

Hyposulphurous  acid,  H2S3O4,  is  obtained  as  a  zinc  salt  by  the 
action  of  zmc  upon  aqueous  sulphurous  acid:  Zn  +  2H2S03=ZnS204  + 
2H2O;  it  is,  like  its  salts,  only  known  in  aqueous  solution,  which  is  yellow, 
readily  decomposes,  and  is  a  strong  reducmg  and  bleachmg  agent. 


SELENIUM.  131 

Sulphur  heptoxide,  S2O7,  is  produced  by  the  action  of  dark  electrical 
discharges  upon  a  dry  mixture  of  sulphur  dioxide  and  oxygen,  and  forms 
thick  drops  which  solidify  at  0°  and  which,  on  heating,  decompose  into 
2SO3  +  O,  and  with  water  decompose  into  sulphuric  acid  and  oxygen: 
2H,0  +  S207=2H2SO,  +  0. 

Persulphuric  acid,  RgS-^Og,  is  only  known  dissolved  in  sulphuric 
acid  or  as  its  salts;  it  is  produced  by  the  electrolysis  of  40  per  cent,  sul- 
phuric acid,  whereby  this  decomposes  into  its  ions  (p.  75),  SO^  +  Hg, 
and  then  the  ion  SO4  unites  with  a  molecule  of  H2SO4.  Its  salts  or 
persulphates  are  obtained  by  the  action  of  strong  bases  upon  B^O-,  or 
by  the  electrolysis  of  solutions  of  sulphates.  Persulphates,  like  the  acid, 
have  the  properties  of  hydrogen  peroxide,  having  an  oxidizing  as  well  as 
a  reducing  action;  nevertheless  they  do  not  decompose  an  acid  solution 
of  potassium  permanganate  (p.  118),  nor  do  they  react  with  chromic 
acid. 

Oxysulphuric  acid,  H^SOg  or  HO-SO^-O-OH,  is  obtained  by 
mixing  sulphuric  acid  with  hydrogen  peroxide,  persulphates,  sodium 
or  barium  dioxide,  and  is  used  as  one  of  the  most  powerful  oxidizing 
agents  (Caro's  reagent). 

3.  Selenium. 

Atomic  weight  79.2  =  Se. 

Occurs  to  a  slight  extent,  generally  combined,  as  lead  selenide,  PbSe, 
and  as  sulphur  selenide,  SSe.  It  accompanies  most  of  the  metallic  sul- 
phides to  a  slight  extent,  and  deposits  as  a  mud  in  the  lead  chambers 
in  the  sulphuric  acid  manufacture.     It  is  known  in  four  modifications: 

1.  As  amorphous,  black,  vitreous  masses  having  a  specific  gravity  of 
4.28,  soluble  in  carbon  disulphide,  and  obtained  by  quickly  cooling  fused 
selenium. 

2.  As  a  red  amorphous  powder  having  a  specific  gravity  of  4,26,  soluble 
in  carbon  disulphide,  and  obtained  by  the  reduction  of  an  aqueous  solu- 
tion of  selenium  dioxide  by  sulphur  dioxide:  H2Se03  +  2S02  +  H20= 
2H2SO,  +  Se. 

3.  In  dark-red  crystals  isomorphous  with  monoclinic  sulphur  having 
a  specific  gravity  of  4.5,  and  obtained  on  the  evaporation  of  the  solutions 
of  modifications  1  and  2  in  carbon  disulphide. 

4.  As  rhombic,  metallic,  bluish-gray  masses  having  a  specific  gravity  of 
4.8,  insoluble  in  carbon  disulphide,  and  obtained  by  heating  amorphous 
selenium  to  150°  or  by  slowly  cooling  fused  selenium.  Only  this  modifi- 
cation conducts  electricity. 

Selenium  melts  at  217°,  boils  at  680°,  burns  when  heated  in  the  air 
with  a  bluish  flame,  producing  white  crystalline  selenium  dioxide,  SeO,, 
which  has  an  odor  similar  to  radishes.  Selenium  dissolves  in  part  un- 
changed in  fuming  sulphuric  acid,  producing  a  green  color,  another 
part  being  converted  into  selenious  acid:  Se  +  2HjjS04=H2Se03  +  H2S03 
-fSOg. 

4.  Tellurium. 

Atomic  weight  127.6  =  Te. 

Occurs  only  seldom,  either  free  or  combined  with  metals,  as  graphitic 
tellurium,     (AuAg3)Te3,      tetradymite,    BigTca  +  Bi^Sg,    silver    telluride, 


132  INORGANIC  CHEMISTRY, 

AgjTe,  lead  telluride,  PbTe,  etc.  All  tellurium  ores  dissolve  in  hot  con- 
centrated acid  with  a  red  color.  Two  modifications  of  tellurium  are 
known : 

1.  As  amorphous,  black  powder  having  a  specific  gravity  of  5.9,  ob- 
tained on  the  reduction  of  an  aqueous  solution  of  tellurium  dioxide  by 
sulphur  dioxide:  H2Te03  +  2S02  +  H20  =  Te  +  2H2SO,. 

2.  As  rhombic,  metallic,  silvery  crystalline  masses  having  a  specific 
gravity  of  6.2  and  obtained  by   cooling  fused  amorphous  tellurium. 

Tellurium  conducts  heat  and  electricity,  melts  at  450°,  boils  at  about 
1390°,  and  burns  when  heated  in  the  air  with  a  blue  flame,  formmg  white 
crystalline  tellurium  dioxide,  TeOj. 

HALOGEN  GROUP. 
Fluorine.     Chlorine.     Bromine.     Iodine. 

These  monovalent  elements  differ  from  all  other  elements  by  the 
fact  that  their  compounds  with  hydrogen  are  strongly  acid  and  their 
compounds  with  metals  are  the  salts  of  these  acids;  hence  these  elements 
have  also  been  called  halogens,  haloids,  salt-formers  («/l5,  salt,  yevvaGo, 
to  form);  their  hydrogen  acids,  halogen  acids;  and  their  salts,  halogenides 
or  haloid  salts. 

With  an  increase  in  atomic  weight  their  affinity  for  hydrogen  dimin- 
ishes and  for  oxygen  increases.  Chlorine  expels  bromine  and  iodine 
from  its  hydrogen  compounds,  bromine  expels  iodine  from  these  same 
compounds,  while  iodine,  on  the  contrary,  replaces  bromine  and  chlorine, 
and  bromine  replaces  chlorine,  in  their  oxygen  compounds;  for  instance, 
we  obtain  potassium  periodate  by  treating  a  solution  of  potassium  per- 
chlorate  with  iodine,  while  chlorine  is  evolved:    HC104  +  I=HI04  4-C1. 

The  affinity  of  fluorine  for  oxygen  is  very  sfight,  so  that  its  oxides  and 
oxyacids  have  not  been  obtained  up  to  the  present  time 

The  atomic  weight  and  hence  also  the  vapor  density  of  bromine  is 
about  the  average  of  that  of  chlorine  and  iodine,  and  bromine  stands 
between  these  two  in  all  its  properties. 

I.  Chlorine. 

Atomic  weight  35.45=  CI. 

Occurrence.  Only  in  combination,  in  small  quantities  in  all  parts  of 
animals  and  in  many  plants;  also  as  horn-silver,  AgCl,  as  phosgenite, 
PbCl^,  etc.;  in  larger  quantities  as  carnallite,  MgCl^+KCH-OH^O, 
sylvine,  KCl,  and  rock  salt,  NaCl;  also  combined  with  potassium, 
sodium,  and  magnesium  (which  see),  dissolved  in  sea- water,  in  salt 
springs,  etc. 

Preparation.  1.  By  heating  hydrochloric  acid  (HCl)  with  man- 
ganese dioxide  (MnO;,)  or  other  dioxides; 

Mn024- 4HC1  =  MnCl,+ 2H2O+ 2C1. 


CHLORINE.  133 

The  manganous  chloride  (MnClj)  produced  is  again  converted  into 
MnO,  in  technical  pursuits  (Weldon's  process,  see  Manganous  Chloride). 

2.  By  heating  sodium  chloride  with  manganese  dioxide  and 
sulphuric  acid:  Mn02+2NaCl+2H2S04=MnS04+Na2S04+2H20+ 
2C1. 

3.  By  pouring  hydrochloric  acid  or  sulphuric  acid  upon  chloride 
of  lime  (calcium  hypochlorite):  Ca(OCl)2+4HCl  =  CaCl2+2H20+4Cl 
(see  Chloride  of  Lime). 

All  other  hypochlorites  behave  like  calcium  hypochlorite  towards 
hydrochloric  acid,  also  all  chlorites  and  chlorates,  as  well  as  many  other 
salts  rich  in  oxygen  (potassium  dichromate,  potassium  permanganate). 
These  bodies  are  therefore  used  in  the  preparation  of  small  quantities  of 
chlorine. 

4.  On  the  electrolysis  of  an  aqueous  solution  of  hydrochloric 
acid,  HCl  (p.  136). 

Technical  Preparation.  1.  Nearly  entirely  by  the  electrolysis  of  fused 
metallic  chlorides  as  a  by-product  in  the  preparation  of  the  respective 
metals  or  metallic  hydroxides  (see  Potassium),  or  by  the  electrolysis  of 
their  aqueous  solution. 

2.  Hydrochloric  acid  is  mixed  with  air  and  passed  over  heated 
bricks  (Deacon's  process):  2HC1  +  0=H20  +  2C1;  this  decomposition 
takes  place  more  readily  when  the  bricks  are  previously  impregnated 
with  copper  sulphate  solution  (CUSO4);  this  cupric  salt  remains  un- 
changed and  can  be  used  for  a  long  time  (Catalysis,  p.  66). 

3.  Magnesium  chloride,  so  often  obtained  as  a  by-product,  decomposes 
in  part  on  evaporating  its  watery  solution  into  hydrochloric  acid  and 
magnesium  oxide:  MgCl2  +  H20  =  MgO  +  2HCl;  the  magnesium  oxy- 
chloride,  MgCU  +  MgO,  which  remains  behind,  decomposes  on  heating 
in  a  current  of  air  into  magnesium  oxide  and  chlorine. 

4.  On  heating  calcium  or  magnesium  chloride,  so  extensively  ob- 
tained as  a  by-product,  with  sand  in  a  current  of  air,  we  obtain  chlorine: 
CaCl2  +  Si02  +  0=CaSi03  +  2Cl. 

Properties.  A  greenish-yellow  {x^oop6<i,  greenish  yellow),  poisonous 
gas,  2.5  times  heavier  than  air,  having  an  irritating  odor,  and  strongly 
attacking  the  respiratory  organs,  liquefiable  at  — 40°,  forming  a  yellow 
liquid  which  is  heavier  than  water  and  not  miscible  therewith,  and 
which  solidifies  at  - 102°  into  yellow  crystals.  Liquid  chlorine  does  not 
attack  iron,  and  is  sold  in  commerce  in  iron  cylinders  (p.  41).  One 
volume  of  water  dissolves  2,5  volumes  of  chlorine  at  10°;  on  this  ac- 
count, and  as  it  combines  with  mercury,  we  collect  this  gas  over  hot 
water  or  saturated  NaCl  solution. 


134  INORGANIC  CHEMISTRY, 

Chlorine- water  is  a  solution  of  chlorine  in  water  which  contains  0.4 
to  0.5  per  cent,  by  weight;  it  must  be  kept  in  the  dark,  as  daylight  slowly 
and  sunlight  more  rapidly  decomposes  it  with  the  formation  of  oxygen 
and  hydrochloric  acid :  HjO  +  2C1  =  2HC1  +  O.  If  saturated  chlorine- water 
is  cooled  to  0°,  yellow  crystals  of  chlorine  hydrate,  Cla  +  lOHjO,  separate 
out. 

It  combines  directly  with  all  elements  with  the  exception  of 
argon,  hehum,  nitrogen,  carbon,  oxygen,  and  certain  of  the  rare 
platinum  metals.  Phosphorus,  thin  sheets  of  gold  and  copper, 
powdered  arsenic,  antimony,  boron,  siUcon,  bismuth,  combine  in 
chlorine  gas  even  at  ordinary  temperatures  and  burn  brightly  therein. 
Chlorine  has  very  strong  affinities  for  hydrogen;  a  mixture  of  equal 
volumes  of  chlorine  and  hydrogen  combines  gradually  in  diffused 
dayUght,  while  in  sunlight  it  immediately  explodes,  producing 
hydrochloric  acid.  A  hydrogen  flame  burns  in  chlorine  gas  and 
vice  versa  (p.  109).  Many  organic  compounds  which  contain 
carbon  and  hydrogen  lose  their  hydrogen  with  the  formation  of 
hydrochloric  acid;  thus  paper  moistened  with  turpentine  (a  com- 
pound of  carbon  with  hydrogen)  when  introduced  into  chlorine 
inflames^  and  carbon  is  set  free.  Chlorine  is  not  combustible  in 
the  air,  but  supports  the  combustion  of  a  candle  or  illuminating- 
gas  (a  mixture  of  hydrocarbons)  with  the  setting  free  of  carbon 
(soot).  This  phenomenon  may  be  explained  by  the  union  of  the 
hydrogen  of  the  respective  compound  with  chlorine  and  the  setting 
free  of  heat,  which  heats  the  gas  to  a  red  heat,  while  the  carbon 
present  separates  out. 

Chlorine  destroys  all  natural  and  many  artificial  coloring  matters, 
as  it  combines  with  the  same  or  oxidizes  them,  since  in  the  presence  of 
water  it  unites  with  the  hydrogen  of  the  body  and  sets  free  nascent 
oxygen:  H20-f-2Cl  =2HCH-0.  Its  disinfecting  action,  that  is,  the 
destruction  of  infectious  and  odoriferous  substances  by  chlorine, 
also  depends  upon  this  fact.  (Use  of  chlorine  in  the  presence  of 
water  for  bleaching  and  disinfection.) 

Dry  chlorine  shows  much  less  chemical  activity  than  moist  chlorine 
and  does  not  attack  metals;  hence  liquid  chlorine  is  sold  in  iron 
cylinders. 

Detection.  1.  Free  chlorine  sets  iodine  free  from  potassium 
iodide,  hence  it  turns  potassium  iodide  and  starch  paste  blue  (p.  111). 

2.  It  decolorizes  indigo  solution  and  moist  htmus  paper. 


CHLORINE.  135 

a.  Compounds  with  Hydrogen. 

Hydrogen  Chloride,  Hydrochloric  Acid,  HCl.  Occurrence,  Free 
in  the  gases  of  volcanoes,  and  to  a  slight  extent  in  gastric  juice. 

Formation.  1.  A  mixture  of  equal  volumes  of  hydrogen  and 
chlorine  may  be  kept  unchanged  in  the  dark;  in  diffused  daylight  they 
unite  gradually;  in  direct  sunlight  they  combine  immediately  with  ex- 
plosive violence,  forming  hydrochloric  acid.  The  volume  of  the  gas 
remains  unchanged. 


iH  iCl     ^      (H  <H 

|H    +      jCl  |C1    ^      jCl 


2.  By  the  action  of  chlorine  upon  water  and  many  organic 
compounds. 

Preparation.  1.  From  crude  hydrochloric  acid  (see  below)  by 
boiling. 

2.  It  is  prepared  on  a  large  scale  in  the  Leblanc  soda  manu- 
facture by  heating  sodium  chloride  with  sulphuric  acid: 

2NaCl  +   H,S04    =   Na^SO^  +    2HC1. 

Sodium  Sulphuric  Sodium      Hydrochloric 

chloride.  acid.  sulphate.  acid. 

The  sodium  sulphate  obtained  as  a  by-product  is  used  in  the 
manufacutre  of  glass  or  is  converted  into  sodium  sulphide,  NajS, 
which  is  used  in  the  manufacture  of  cellulose. 

3.  On  a  large  scale  by  passing  superheated  steam  over  magnesium 
chloride  (p.  133),  which  is  obtained  as  a  by-product  in  many  chemical 
processes : 

2MgCl2+  HjO  =  MgO.MgCl2+  2HC1. 

Properties.  Colorless,  irritating  gas  which  is  non- combustible 
and  which  does  not  support  combustion.  It  is  1.25  times  heavier 
than  air,  fumes  in  the  air  (because  it  abstracts  water  therefrom  and 
produces  hydrochloric  acid,  which  separates  as  a  vapor),  liquefiable 
at  —81°,  forming  a  colorless  liquid  which  solidifies  at  —116°. 

One  volume  of  water  dissolves  450  volumes  of  this  gas  at  15° 
and  forms  therewith  a  fuming,  colorless,  strongly  acid  liquid  having 
a  specific  gravity  of  1.21,  which  contains  43  per  cent,  by  weight  of 


136  INORGANIC  CHEMISTRY. 

HCl.     The  watery  solution  of  hydrogen  chloride  is  ordinarily  called 
hydrochloric  acid  or  muriatic  acid. 

Crude  hydrochloric  acid  is  contaminated  by  chlorine,  sulphuric  acid, 
arsenic,  iron,  etc.,  and  hence  is  yellow  in  color.  It  has  a  specific  gravity 
of  1.158  to  1.170  and  contains  from  30  to  33  per  cent.  HCl. 

Pure  hydroctiloric  acid,  obtained  by  the  repeated  distillation  of  crude 
hydrochloric  acid,  is  a  colorless  liquid  of  a  specific  gravity  of  1.20  and 
contains  39.1  per  cent.  HCl. 

Dilute  hydrochloric  acid  consists  of  equal  parts  water  and  pure  hydro- 
chloric acid. 

On  heating  concentrated  hydrochloric  acid  it  yields  HCl  until  the 
residue  contains  20  per  cent.  HCl;  this  hydrochloric  acid  has  a  specific 
gravity  of  1.10  and  distils  without  decomposition  at  110°;  dilute  hydro- 
chloric acid  on  heating  gives  off  water  until  the  residue  contains  20  per 
cent.  HCl  (p.  53). 

If  the  electric  current  is  passed  by  means  of  carbon  electrodes 
(as  the  chlorine  set  free  would  attack  metals)  through  an  aqueous 
solution  of  hydrogen  chloride,  equal  volumes  of  hydrogen  and  chlorine 
are  set  free  at  the  negative  and  the  positive  pole  respectively. 

If  hydrochloric  acid  gas  is  passed  over  heated  potassium  or  sodium, 
one-half  its  volume  of  hydrogen  is  set  free:   Na+HCl  =  NaCl+H. 

Hydrochloric  acid  dissolves  most  metals  with  the  formation  of 
chlorides  and  the  evolution  of  hydrogen:  2HC1+Zn  =ZnCl2+2H; 
only  mercury,  silver,  copper,  gold,  arsenic,  anitmony,  bismuth,  lead, 
and  the  platinum  metals  are  not  attacked  by  this  acid,  or  only  to  a 
slight  extent. 

Chlorides  are  obtained  by  the  direct  union  of  the  elements,  but 
ordinarily  by  the  action  of  hydrochloric  acid  upon  metals,  metallic 
oxides,  or  metallic  hydroxides. 

Detection.  1.  When  heated  with  dioxides,  hydrochloric  acid 
forms  chlorides  with  the  setting  free  of  chlorine  (p.  132). 

2.  Hydrochloric  acid  and  soluble  chlorides  give  with  silver  nitrate 
a  white,  cheesy  precipitate  of  silver  chloride  (AgCl)  which  darkens  in 
the  light  and  which  is  soluble  in  ammonia,  but  not  soluble  in  nitric 
acid:    HCl+AgN03=AgCl+HN03. 

3.  Lead  salts  precipitate  white  lead  chloride  (PbCy,  soluble  in 
hot  water  or  considerable  cold  water: 

PbCNO,)  +  2HC1  =  PbCl^-h  2HNO3. 


CHLORINE,  137 

6.  Compounds  with  Oxygen. 

Chlorine  monoxide,    C1,0.  Hypochlorous  acid,  HCIO. 

Chlorine  dioxide,        ClO^.  — 

(Chlorine  trioxide,     ClgOg.)  (Chlorous  acid,  HClOa-) 

Chlorine  tetroxide,     ClgO^.  — 

(Chlorine  pentoxide,  ClgOg )  Chloric  acid,  HCIO3. 

Chlorine  heptoxide,    CljjO;.  Perchloric  acid,  HCIO4. 

Chlorine  trioxide  and  chlorine  pentoxide  are  only  known  mixed  as 
chlorine  tetroxide;  chlorous  acid  is  only  known  in  the  form  of  its  salts, 
the  chlontes  (p,  138). 

Chlorine  Monoxide,  Cl^O.  Preparation  Cooled  chlorine  gas  is  passed 
over  mercury  oxide  (HgO)  and  the  vapors  produced  condensed  m  a 
coohng  mixture:    HgO  +  4Cl=HgCl2  +  Cl20. 

Properties.  It  forms  a  red  liquid  which  boils  at  +5°  and  then  forms 
a  yellowish-red,  poisonous,  strongly  oxidizing  gas  with  a  disagreeable 
odor.  It  soon  decomposes  into  its  constituents,  which  can  be  brought 
about  especially  by  shock,  heating,  or  in  contact  with  oxidizing  sub- 
stances, often  with  an  explosion. 

Hypochlorous  Acid,  HCIO.  Preparation.  Chlorine  monoxide  is  very 
soluble  in  water,  forming  hypochlorous  acid:  Cl20  +  H,^0=2HC10;  on 
concentration  this  splits  into  chlorine  monoxide  again,  so  that  anhydrous 
HCIO  is  not  known. 

Properties.  The  dilute,  nearly  colorless  solution  may  be  distilled  with- 
out decomposition;  the  concentrated  yellow  solution  decomposes  on 
heating  and  in  the  sunlight  with  the  formation  of  chloric  acid  and  chlo- 
rine: 3HC10  =  2HC1  +  HC10,;  2HC10  +  2HC1=4C1  +  2H20.  With  hydro- 
chloric acid  it  evolves  all  the  chlorine  of  both  compounds:  HC10  +  HC1= 
H2O+CI2  It  IS  a  very  weak  acid,  which  does  not  decompose  carbonates, 
but  is  a  very  strong  oxidizing  agent. 

Hypochlorites  are  also  readily  decomposable  and  strong  oxidizing 
agents.  They  are  prepared  by  saturating  HCIO  with  the  respective 
bases.  Commercially  they  are  obtained,  mixed  with  chlorides,  by 
passing  chlorine  (generally  electrolytically  prepared)  into  cold  and  dilute 
solutions  of  the  strong  bases: 

2NaOH  +  2C1=  NaClO  +  NaCl  +  H,0. 

Sodium  Sodium        Sodium 

hydroxide-  hypochlorite,  chloride 

Nitric  acid  sets  hypochlorous  acid  free  from  the  hypochlorites,  and 
this  can  be  separated  by  distillation:  NaC10  +  HN03=NaN03  +  HC10. 
Hydrochloric  acid  sets  chlorine  free,  and  certain  metallic  oxides  generate 
oxygen  from  hypochlorites  (see  Chloride  of  Lime). 

Chlorine  Dioxide,  ClO^,  or  Chlorine  Tetroxide,  Clj04  (formerly 
called  Hypochloric  Acid).  Preparation.  Small  quantities  of  potas- 
sium chlorate  (KCIO3)  are  gradually  and  carefully  added  to  concen- 
trated sulphuric  acid  and  then  distilled  at  a  temperature  not  above 


138  INORGANIC   CHEMISTRY, 

30°  in  order  to  prevent  explosion.  The  chloric  acid  first  produced 
decomposes  immediately  by  the  dehydrating  action  of  the  sulphuric 
acid:  3C103H=2C102+H20+C104H.  It  may  be  obtained  with 
less  danger  by  heating  potassium  chlorate  with  oxalic  acid  not  above 
70°. 

Properties.  Reddish-yellow,  oxidizing  gas  with  a  strong  odor, 
liquefiable  in  an  ice  mixture  forming  a  red  liquid  which  boils  at  + 10°; 
these  bodies  are  readily  decomposed  by  organic  substances,  or 
better  by  warming  above  30°  with  explosive  violence,  but  not  by 
sunlight.  Water  dissolves  it  unchanged,  producing  a  yellow  solu- 
tion; alkaU  hydroxides  decolorize  this  solution  with  a  formation  of 
chlorates  and  chlorites:  2CIO2+2KOH  ^KClO^+KClOg+H^O,  so 
that  the  compound  may  be  considered  as  the  mixed  anhydrides  of 
chlorous  and  chloric  acids  (Cl205+Cl203=2Cli,04). 

The  molecule  seems  at  lower  temperatures  to  have  the  composition 
CI2O4,  and  on  passage  into  the  gaseous  condition  it  decomposes  into  two 
molecules,  ClOj*.  hence  this  behavior  to  alkalies,  as  well  as  the  analogy 
with  NO2  and  NgO^. 

Chloric  Acid,  HCIO3.  Preparation.  Only  its  aqueous  solution, 
containing  40  per  cent.  HCIO3,  is  known.  This  is  obtained  by  decom- 
posing barium  chlorate  with  dilute  sulphuric  acid,  filtering  off  the 
insoluble  barium  sulphate,  and  concentrating  the  solution  under  the 
air-pump  receiver :   Ba(C103)2+  H2SO4  =  BaS04+  2HCIO3. 

Properties.  Thick,  odorless  and  colorless,  acid  liquid,  which 
on  further  evaporation  under  the  air-pump,  also  in  light  or  on  warm- 
ing to  40°,  decomposes  into  chlorine,  oxygen,  and  perchloric  acid 
(which  see).  It  has  such  a  strong  oxidizing  action  that  on  pouring  it 
upon  alcohol,  phosphorus,  paper,  etc.,  they  inflame;  with  hydrochloric 
acid  it  generates  chlorine:   tlClOg+SHCl  ^SHjO+GCl. 

Chlorates  are  obtained,  mixed  with  chlorides,  when  chlorine 
(generally  obtained  as  a  by-product  in  the  electrolytic  soda  manu- 
facture) is  passed  into  hot  and  concentrated  solutions  of  bases  (see 
Hypochlorites,  p.  137):    6KOH+6CU5KCI+KCIO3+3HA 

Chlorates  readily  give  off  their  oxygen  and  therefore  decompose 
with  explosive  violence  when  they  are  rubbed  or  heated  with  inflam- 
mable or  oxidizable  bodies,  such  as  phosphorus,  sulphur,  antim.ony 
sulphide,  sugar,  etc.  The  inflammable  mass  of  the  Swedish  match 
consists  of  antimony  sulphide  and  potassium  chlorate,  and  inflames 


BROMINE,  139 

on  friction  with  the  red  phosphorus  contained  on  the  sides  of  the  box. 
Silver  nitrate  does  not  precipitate  the  chlorates  from  their  solution; 
when  heated  alone  they  decompose  without  explosion  into  per- 
chlorates  (see  below)  and  then  into  chlorides  and  oxygen.  When 
hydrochloric  acid  is  poured  upon  chlorates  they  generate  chlorine 
besides  some  CIO2:  KC103+6HC1  =  KC1+3H20+6C1;  when  heated 
with  sulphuric  acid  they  yield  chlorine  dioxide  (p.  137). 

Chlorine  heptoxide,  C\0^,  is  obtained  by  distilling  perchloric  acid 
with  phosphorus  pentoxide,  2HC104  +  P205=2HP03-f-Cl207,  as  a  thick, 
colorless  liquid.  It  has  only  a  slight  action  upon  oxidizable  substances, 
but,  on  the  contrary,  when  ignited  or  struck  it  explodes  with  violence. 
It  is  soluble  in  water,  forming 

Perchloric  Acid,  HCIO^.  Preparation.  From  chloric  acid  by  ex- 
posure to  light  or  warmth:  3HC103=HC104  +  H20  +  2Cl  +  40;  ordinarily 
by  distilling  potassium  perchlorate  with  sulphuric  acid:  2KC10.  + 11,804= 
I4S0,  +  2HC10,. 

Properties.  Colorless,  fuming  liquid,  which  readily  oxidizes  and 
therefore  inflames  carbon,  paper,  wood,  and  other  organic  bodies  with 
explosion;  it  produces  painful  sores  on  the  skin,  and  decomposes  with 
explosion  after  a  few  days,  even  in  the  dark.  On  the  contrary,  its  aqueous 
solution  is  stable,  non-oxidizing,  and  not  decomposable  by  hydrochloric 
or  sulphuric  acids. 

Perchlorates  are  obtained  at  the  positive  pole  on  the  electrolysis  of 
an  aqueous  solution  of  chlorides  by  the  oxygen  evolved  at  that  pole,  or 
by  heating  potassium  chlorate  somewhat  above  its  melting-point,  when 
a  part  of  its  oxygen  is  first  given  off  and  it  is  converted  into  potassium 
perchlorate  and  potassium  chloride:  2KC103=KC104  +  KCl  +  02.  At  a 
higher  temperature  the  potassium  perchlorate  is  completely  decomposed 
into  potassium  chloride  and  oxygen.  Perchlorates  differ  from  the 
chlorates  in  that  they  are  not  attacked  by  hydrochloric  acid  and  do  not 
yield  explosive  chlorine  dioxide  with  sulphuric  acid,  as  well  as  by  their 
msolubility  in  water.     Sodium  perchlorate  is  found  in  Chili  saltpeter. 

c.  Compounds  with  Sulphur. 

Sulphur  monochloride,  SJCI^,  and  sulphur  dichloride,  SCI2,  are  ob- 
tained by  the  action  of  chlorine  upon  warmed  sulphur  as  reddish-yellow 
liquids  decomposible  by  water.  The  first  dissolves  about  70  per  cent,  of 
sulphur  and  is  used  in  the  vulcanization  of  rubber. 

Sulphur  tetrachloride,    SCl^,  is  only  stable  below  0°. 

2.  Bromine. 

Atomic  weight  79.96=  Br. 

Occurrence.  Bromine  only  occurs  combined  chiefly  with  sodium 
and  magnesium  in  sea-water  and  in  all  plants  and  animals  living 
therein,  in  many  salt  springs  (Kreuznach,  Kissingen)  and  salt  deposits, 


140  INORGANIC  CHEMISTRY. 

especially  in  the  Stassfurt  "abraum"  salts  (see  Potassium  Chloride). 
It  occurs  in  traces  with  iodine  in  the  thyroid  gland.  Silver  bromide 
forms  the  mineral  called  bromite. 

Preparation.  On  the  partial  evaporation  of  sea-water  the  more 
insoluble  chlorides  separate  out  first  and  the  readily  soluble  bromine 
salts  remain  in  solution;  from  this  mother-liquor  (p.  52)  or  from  the 
mother-liquor  from  the  "  abraum  "  salts  (see  Potassium)  the  bromine 
may  be  obtained  by  distilhng  with  manganese  dioxide  and  sulphuric 
acid:  2KBr+Mn02+2H2S04  =  2Br+K2S04+MnS04+2H,0,  or  by 
passing  chlorine  therein  and  heating:  KBr+Cl  =  KCl+Br,  or  by 
electrolysis  when  the  bromine  set  free  remains  in  solution  and  is 
driven  off  by  distillation. 

Properties.  Dark  reddish-brown,  poisonous  and  caustic  liquid 
(the  only  liquid  element  at  ordinary  temperatures  besides  mercury) 
having  a  specific  gravity  of  3.18  at  0°,  boils  at  63°  and  is  very  volatile 
at  ordinary  temperatures,  and  solidifies  at  —  8°,  forming  a  crystalline 
reddish-brown  mass.  It  has  a  peculiarly  unpleasant  odor  (ySpc5yuo5, 
stench),  attacks  the  skin,  and  its  yellowish-brown  vapors  have  a 
powerful  action  upon  the  mucous  membranes.  Bromine  dissolves  in 
30  parts  water  (bromine- water) ,  also  readily  in  ether,  alcohol,  carbon 
disulphide,  and  chloroform,  with  a  brownish-red  color.  With  water  it 
forms  at  0°  crystalline,  yellow  bromine  hydrate,  BrjH-  lOHjO.  Chemi- 
cally bromine  has  great  similarity  to  chlorine,  but  has  less  affinitj^  for 
the  elements  than  this;  it  decomposes  water  only  very  slowly,  but  oxid- 
izes many  bodies  in  the  presence  of  water;  hence  it  also  has  a  bleach- 
ing action.  It  unites  with  hydrogen  first  on  heating  and  not  in  the 
sunhght,  and  with  sulphur  it  forms  sulphur  monobromide,  SjBrj. 
Infusorial  earth  impregnated  with  bromine  is  called  solid  bromine. 

Detection.  Bromine  colors  starch  paste  orange,  and  dissolves 
in  carbon  disulphide  or  chloroform,  producing  a  brownish-red  solu- 
tion. 

a.  Compounds  with  Hydrogen. 

Hydrogen  Bromide,  Hydrobromic  Acid,  HBr.  Preparation.  1. 
Hydrogen  and  bromine  first  unite  when  their  vapors  are  passed 
through  a  gently  heated  tube  (generally  filled  with  spongy  platinum 
in  order  to  increase  the  yield,  p.  126). 

2.  By  distillation  of  bromides  wit*h  phosphoric  acid: 
H3PO4+  3NaBr  =  Na3P04+  3HBr. 


BROMINE.  141 

On  the  distillation  of  bromides  with  concentrated  sulphuric  acid 
we  also  obtain  hydrobromic  acid,  but  this  in  part  is  immediately 
decomposed  so  that  also  free  bromine  and  sulphur  dioxide  are  pro- 
duced :   2HBr+  H.SO^  =  2H2O+  2Br+  SO^. 

3.  If  phosphorus  bromide  is  warmed  with  water,  or  if  we  allow 
bromine  to  flow  into  amorphous  phosphorus  under  water,  we  obtain 
hydrobromic  acid: 

PBr3+  3H2O  =  3HBr+  H3PO3. 

Phosphorus  Phosphorous 

bromide.  acid. 

4.  By  passing  H2S  into  water  containing  bromine  and  expelling 
the  excess  of  H2S  by  careful  warming,  we  obtain  an  aqueous  solution 
of  hydrobromic  acid:    H2S+2Br  =  2HBr+S. 

Hydrobromic  acid  may  also  be  obtained  by  the  action  of  Br 
upon  organic  hydrogen  compounds  such  as  naphthalene,  CjoHg. 

Bromides  are  obtained  in  a  manner  analogous  to  the  chlorides 
(see  also  Potassium  Bromide). 

Properties.  Colorless  gas,  irritating  odor,  fumes  in  the  air,  partly 
decomposes  at  800°,  Uquefiable  at  —73°  and  solidifying  at  -120°, 
and  very  readily  soluble  in  water.  Its  watery  solution  boils  at  125° 
(p.  53)  and  then  contains  48  per  cent.  HBr  and  has  a  specific  gravity 
of  1.49.  This  solution  turns  red  in  the  air,  due  to  the  separation  of 
bromine :   2HBr+  O  =  H2O+  2Br. 

Detection.  1.  Silver  nitrate  precipitates  yellowish-white  silver 
bromide,  AgBr,  from  solutions  of  HBr  or  of  bromides.  This  precipi- 
tate is  insoluble  in  nitric  acid,  but  soluble  in  considerable  ammonia, 
and  darkens  in  the  light. 

2.  If  a  solution  of  HBr  or  a  bromide  is  treated  with  chlorine- 
water,  the  bromine  is  set  free,  which,  when  shaken  with  carbon 
disulphide,  gives  a  reddish-brown  color  thereto. 

h.  Compounds  with  Oxygen. 

Hypobromous  acid,  HBrO. 
Bromic  acid,  HBrOg. 

Perbromic  acid,         HBrO^, 

At  the  present  time  we  do  not  know  of  any  oxide  of  bromine,  but  only 
the  above-mentioned  oxyacids,  and  these  indeed  only  in  watery  solu- 
tion. They  are  prepared  in  the  same  manner  as  the  corresponding 
chlorine   compounds. 


142  INORGANIC  CHEMISTRY, 

Hypobromites,  bromates,  and  perbromates  are  obtained  in  the 
same  manner  as  the  chlorine  compounds  and  have  great  similarity 
therewith. 

3.  Iodine. 

Atomic  weight  126.85=1. 

Occurrence.  Only  combined  with  potassium,  sodium,  calcium, 
magnesium  in  certain  salt  springs  and  to  a  less  extent  in  sea-water, 
from  which  many  sea  animals  and  all  algae  remove  it;  also  in  Chili  salt- 
peter and  in  certain  rock  salts,  in  many  plants,  in  muscle-tissue,  blood, 
in  cow's  milk  and  hen's  eggs,  in  fresh-water  animals,  and  in  the 
thyroid  gland.  It  occurs  rarely  as  silver  iodide  and  lead  iodide  in 
certain  minerals. 

Preparation.  1.  Seaweeds  are  burnt  and  the  ash  (kelp  or  varec) 
lixiviated  with  water;  the  less  soluble  chlorides  are  removed  from 
this  solution  in  part  by  evaporation  and  the  remaining  liquid  (the 
mother-liquor)  is  distilled  with  manganese  dioxide  and  sulphuric 
acid  or  chlorine  pass  through  the  solution,  when  the  iodine  is  obtained 
(same  process  as  with  bromine,  p.  140). 

2.  The  mother-liquor  of  Chili  saltpeter  contains  sodium  iodate, 
from  which  the  iodine  can  be  set  free  and  obtained  by  heating  and 
passing  sulphur  dioxide  through  the  solution:  2NaI03+ 5SO2+ 4H2O 
=  Na2S04+4H2SO,+  2I. 

Properties.  Steel-gray,  poisonous,  metallic-like  plates,  having  a  spe- 
cific gravity  of  4.94,  melting  at  116°,  and  forming  violet  {^ood?/^^  violet) 
vapors  at  183°.  Iodine  evaporates  even  at  ordinary  temperatures, 
has  a  peculiar  odor,  and  combines  with  hydrogen  only  at  a  red  heat. 
It  does  not  decompose  water,  but  oxidizes  many  substances  in  the 
presence  of  water,  and  colors  the  skin  brown.  Only  traces  of  iodine 
are  soluble  in  water,  but  it  is  readily  soluble  in  ether  and  alcohol, 
producing  a  brown  solution  (tincture  of  iodine),  and  in  an  aqueous 
potassium  iodide  solution  (Lugol's  solution),  and  in  chloroform 
and  carbon  disulphide,  forming  a  violet-colored  solution.  Chemi- 
cally it  behaves  very  similar  to  bromine  and  chlorine,  and  is  separated 
from  its  metallic  compounds  by  these  bodies. 

Iodine  unites  with  chlorine,  forming  liquid,  brown  iodine  monochloride, 
ICl,  or  iodine  trichloride,  ICI3,  which  form  orange-yellow  needles.  It 
forms  brown  crystals  of  IBr  with  bromine  and  does  not  combine  with 
sulphur. 


IODINE.  143 

Detection.  Iodine  in  the  presence  of  iodides  gives  a  deep-blue  color 
with  starch  paste  which,  on  warming,  forms  a  colorless  compound; 
by  this  reaction,  as  well  as  by  its  violet  solution  in  carbon  disulphide 
or  chloroform,  the  smallest  quantities  of  iodine  may  be  detected 

a.  Compounds  with  Hydrogen, 

Hydrogen  Iodide,  Hydriodic  Acid,  HI.  Preparation.  In  a  manner 
similar  to  hydrobromic  acid  (p.  140). 

Properties.  Colorless  gas,  readily  decomposable,  fuming  in  the 
air,  liquefiable  at  -34°  and  sohdifying  at  -51°,  readily  soluble  in 
water.  The  watery  solution  shows  a  constant  boiling-point  at  127° 
and  then  contains  37  per  cent.  HI  and  has  a  specific  gravity  of  1.67 
(p.  53).  At  518°  HI  begins  to  decompose;  it  is  decomposed  by 
oxygen  or  oxidizing  substances :  2HI+  O  =  H2O+  21;  hence  it  is  a  strong 
reducing  agent.  With  iodic  acid  all  the  iodine  of  both  compounds 
is  set  free:  5HI+HI03  =  6I+3H20. 

Iodides  are  obtained  in  the  same  manner  as  the  chlorides  (see 
also  Potassium  Iodide). 

Detection.  1.  Silver  nitrate  precipitates  pale-yellow  silver  iod- 
ide, Agl,  from  the  solution  of  HI  or  iodides.  This  precipitate  is 
insoluble  in  ammonia  (differing  from  AgCl  and  AgBr)  and  nitric  acid. 
When  pure  Agl  is  rather  stable  in  sunlight. 

2.  Chlorine  and  bromine  set  iodine  free  from  a  solution  of  HI 
or  iodides.  This  may  be  detected  by  its  violet  solution  in  carbon 
disulphide  or  chloroform,  and  by  its  turning  starch  paste  blue. 

h.  Compounds  with  Oxygen. 

—  Hypoiodous  acid,  HIO 
Iodine  pentoxide,  I^Og.  Iodic  acid,  HIO3. 

—  Periodic  acid,         HIO4. 

Hypoiodous  acid,  HIO,  is  only  known  in  the  form  of  its  salts,  the 
hypoiodites,  which  are  obtained  in  addition  to  iodides  on  dissolving  iodine 
in  dilute  cold  solutions  of  bases  (p.  137),  but  which  quickly  decompose 
into  iodides  and  iodates:    3NaIO=NaI03  +  2NaI. 

Iodine  pentoxide,  I2O5,  is  produced  on  warming  iodic  acid  to  170° 
and  is  a  white,  crystalline  powder,  which  decomposes  into  I2  +  O5  at 
300°  and  is  soluble  in  water,  producing  iodic  acid,  HIO3. 

Iodic  acid,  HIO3,  is  obtained  by  heating  iodine  with  fuming  nitric 
acid:  3I  +  5HN03=3HI03  +  5NO  +  H20,  or  from  iodine  pentoxide  (see 
above).     It  forms  colorless,  rhombic  crystals  which  are  soluble  in  water. 

Iodates  are  obtained  mixed  with  iodides  by  dissolving  iodine  in  bases 


144  INORGANIC  CHEMISTRY. 

and  evaporating  to  dryness  (see  HIO3).  Sulphur  dioxide  (p.  126), 
HgS,  HI,  and  other  reducing  agents  set  iodine  free  from  iodic  acid  and 
iodates. 

Periodic  acid,  HIO4,  is  only  known  as  HglOg  with  2  mol.  water, 
forming  colorless  crystals.  It  is  prepared  by  the  action  of  iodine  upon 
a  solution  of  perchloric  acid  (p.  132). 

Periodates  are  obtained  by  passing  chlorine  into  a  hot  alkaline  solu- 
tion of  the  iodate. 

4.  Fluorine. 

Atomic  weight  19  =F. 

Occurrence.  Free  in  certain  fluor-spars,  but  combined  especially 
as  fluor-spar,  CaFg,  cryoUte,  SNaF+AlFg,  also  in  phosphorite  and 
apatite  (see  Phosphorus).  It  occurs  to  a  slight  extent  in  mineral 
springs,  ashes  of  plants,  and  as  CaFj  in  bones  and  teeth. 

Preparation.  Anhydrous  hydrofluoric  acid  (which  contains  potas- 
sium fluoride  in  solution  in  order  to  make  it  a  conductor)  is  electro- 
lyzed  at  —  20°  in  an  apparatus  of  copper  or  platinum  (as  free  fluorine 
combines  with  all  other  metals);  fluorine  is  set  free  at  the  anode, 
which  consists  of  platinum-iridium  alloy:   HF  =  H+F. 

Properties.  A  greenish-yellow  gas  1.26  times  heavier  than  air, 
produces  irritation  of  the  respiratory  organs,  liquefies  at  —187°, 
forming  a  pale-yellow  liquid  which  at  this  low  temperature  has 
hardly  any  chemical  affinity.  Fluorine  combines  with  bromine, 
iodine,  sulphur,  arsenic,  antimony,  boron,  phosphorus,  silicon,  and 
carbon,  even  at  ordinary  temperatures,  with  the  production  of  flame 
(not  with  the  other  metalloids),  also  with  the  metals  on  gently  warm- 
ing and  with  gold,  platinum,  and  copper  at  higher  temperatures.  It 
inflames  alcohol,  ether,  turpentine,  benzol,  and  many  other  organic  " 
compounds,  as  the  fluorine  combines  with  the  hydrogen  contained 
therein.  It  combines  with  hydrogen  at  —25°  even  in  the  dark,  and 
with  water  it  yields  HF  and  oxygen  containing  ozone;  it  decomposes 
the  metallic  compounds  of  bromine,  chlorine,  and  iodine;  and  it 
does  not  attack  glass  (see  below). 

Compounds  of  Fluorine. 

Hydrogen  Fluoride,  Hydrofluoric  Acid,  HF.  Occurrence.  Only 
as  its  salts,  the  fluorides. 

Preparation.  By  heating  fluorine  compounds  with  concentrated 
sulphuric  acid  in  a  platinum  or  lead  retort.     It  is  also  produced  as 


NITROGEN  GROUP.  145 

a  by-product  ih  the  manufacture  of    superphosphates   (fertilizers) 
from  bones:  CaF2+ H2SO4  =  CaSO,+ 2HF. 

Properties.  Colorless,  strongly  fuming,  poisonous,  and  irritating  gas 
which  Uquefies  on  coohng,  forming  a  colorless,  volatile  liquid,  which 
boils  at  19°  and  sohdifies  at  - 102.5°.  It  dissolves  all  metals  with 
the  evolution  of  hydrogen,  producing  fluorides  with  the  exception 
of  gold,  platinum,  and  lead.  When  anhydrous,  or  when  it  contains 
water,  it  attacks  glass  and  dissolves  the  same  as  it  forms  with  the 
sihcon,  the  chief  constituent  of  glass,  a  gaseous  compound,  sihcon 
fluoride,  SiF^.  The  solution  in  water  may,  therefore,  only  be  kept  in 
lead,  platinum,  paraffine,  or  gutta-percha  bottles.  This  solution  in 
water  boils  constantly  at  120°  and  then  contains  35  per  cent.  HF  and 
has  a  specific  gravity  of  1.15.  It  is  used  in  etching  glass  and  porcelain 
and  to  dissolve  sihcic  acid  compounds  which  are  not  attacked  by 
other  acids:  Si02+4HF  =  SiF4+2H20.  It  prevents  the  acid  fer- 
mentation of  milk  and  hence  is  used  in  fermentive  pursuits. 

Fluorides  are  obtained  by  the  action  of  HF  upon  the  metals 
They  are  all  soluble  in  HF;    silver  fluoride  and  most  of  the  other 
fluorides  are  soluble  in  water,  while  the  fluorides  of  the  calcium  group 
are  insoluble  in  water. 

Detection.  Hydrofluoric  acid  etches  glass;  the  fluorides  on  being 
heated  in  a  lead  crucible  with  sulphuric  acid  evolve  hydrofluoric 
acid  vapors  which  are  allowed  to  act  upon  a  glass  plate  that  has 
been  covered  with  wax  and  a  portion  of  the  wax  removed;  after  "^he 
removal  of  the  wax  the  marking  may  be  seen  upon  its  surface. 

NITROGEN   GROUP. 

Nitrogen.     Phosphorus.     Arsenic.     Antimony. 
Bismuth.     Vanadium.     Tantalum.     Niobium. 

These  elements  form  similarly  constituted  compounds,  in  which  they 
occur  either  trivalent  or  quadrivalent.  In  this  group  also,  as  the  atomic 
weight  increases  the  vapor  density,  the  melting-  and  boiling-point,  as 
well  as  the  metallic  character,  increase  also. 

The  elements  of  the  second  series  (Bismuth,  etc.)  have  a  perfect 
metallic  character,  hence  will  be  discussed  in  connection  with  the  metals; 
and  they  do  not  combine  with  hydrogen,  while  the  elements  of  the  first 
series  form  gaseous  compounds  with  three  atoms  of  hydrogen. 

The  basic  character  of  these  hydrogen  compounds,  as  well  as  the 
acid-forming  power  of  the  oxides,  diminishes  with  the  increase  in  metallic 
properties.  Ammonia  (NH3)  has  strong  basic  properties  and  unites 
with  aU  acids  forming  salts;    phosphureted    hydrogen  (PH3)  combines 


146  INORGANIC  CHEMISTRY. 

only  with  HBr  and  HI ;  arseniureted  hydrogen  (AsHg)  and  antimoniureted 
hydrogen  (SbHg)  have  no  more  basic  properties. 

While  all  the  oxides  of  nitrogen,  phosphorus,  and  arsenic  have  pro- 
nounced acidic  character,  the  antimony  trioxide  shows  besides  the  property 
of  a  weak  acid  anhydride  also  that  of  a  basic  anhydride,  and  bismuth 
trioxide  has  only  basic  properties.  All  of  these  pentoxides  are  acid 
anhydrides;  the  acid  derived  from  bismuth  pentoxide  is  unstable. 

1.  Nitrogen. 

Atomic  weight  14.04=  N. 

Occurrence.  Free  to  a  slight  extent  in  the  gases  of  many  springs 
and  of  volcanoes,  mixed  with  oxygen  in  the  air  where  it  occurs  as 
78  volumes  per  cent. ;  combined  chiefly  as  potassium  nitrate,  KNO,, 
and  sodium  nitrate,  NaNOg,  which  latter  body  is  found  to  a  great 
extent  in  South  America  and  called  Chili  saltpeter.  It  is  also  found 
combined  in  the  most  important  parts  of  plants  and  animals  (pro- 
teids,  blood,  muscle,  nerve  substance,  etc.),  in  fossil  plants  (coal),  in 
guano,  and  as  ammonia  (p.  147). 

Formation.  1.  By  burning  phosphorus  in  air  contained  under  a 
bell-jar  over  water,  the  phosphorus  combines  with  the  oxygen  of 
the  air,  forming  phosphorus  pentoxide  (PjOj),  which  dissolves  in  the 
water,  producing  metaphosphoric  acid,  while  the  nitrogen  of  the  air 
remains. 

2.  In  the  combustion  of  all  nitrogenous  organic  compounds 
with  copper  oxide  in  the  presence  of  copper  (see  Elementary  Analysis). 

Preparation.  1.  By  passing  pure  air  over  red-hot  copper,  when 
copper  oxide  is  formed  and  nitrogen  remains. 

The  nitrogen  obtained  frpm  the  air  always  contains  small  amounts 
of  argon,  helium,  xenon,  krypton,  and  neon  (p.  152),  which  can  only 
be  removed  with  difficulty. 

2.  By  heating  ammonia  nitrite,  which  decomposes  into  water 
and  nitrogen:  NH^N02=2N+2H20;  or  by  boiling  a  solution  of 
potassium  nitrite  (KNOj)  with  ammonium  chloride  (NH^Cl),  when 
ammonium  nitrite  is  first  formed  and  then  this  decomposes  as  above : 

KNO2+  NH.Cl  =  KCl-H  NH.NO^. 

3.  By  passing  chlorine  into  a  saturated  solution  of  ammonia 
(p.  152):  2NH3+6C1  =  2N+6HC1. 


NITROGEN.  '     147 

The  HCl  formed  produces  with  the  still  undecomposed  ammonia, 
white  vapors  of  ammonium  chloride,  NH4CI,  which  dissolve  in  the 
water:   NHj+HCl^NH.Cl  (p.  149). 

4.  By  warming  a  solution  of  ammonia  with  chloride  of  lime: 
3Ca(OCl)2+2NH3  =3CaCl2+3H20+2N. 

Properties.  Colorless,  odorless,  and  tasteless  gas,  shghtly  soluble 
in  water,  and  liquefiable  to  a  colorless  liquid  at  —194°  and  solidifying 
at  —214°  (p.  41).  It  does  not  burn,  neither  does  it  support  com- 
bustion; it  has  an  asphyxiating  action,  not  because  it  is  poisonous, 
but  because  of  the  lack  of  oxygen  (hence  the  French  name  azote  for 
nitrogen:  a,  privative,  and  Zaoeiv,  life).  It  has  a  specific  gravity  com- 
pared with  air  as  unit  of  ..'  q^=Q.97.     Chemically,  nitrogen  is  very 

indifferent;  in  the  cold  it  unites  with  lithium  and  at  a  red  heat  with 
calcium,  barium,  strontium,  magnesium,  boron,  titanium,  silicon,  and 
uranium,  and  the  metals  of  the  rare  earths  forming  so-called  nitrides. 
It  combines  with  hydrogen  and  oxygen  only  at  very  high  temperatures, 
as  under  the  influence  of  the  electric  spark;  nevertheless,  nitrogen 
forms  in  an  indirect  way  a  great  number  of  characteristic  compounds. 

Both  the  nitrogen  atoms  in  the  molecule  are  attached  very  firmly 
to  each  other  and  are  only  separated  from  each  other  at  very  high  tem- 
peratures (also  by  electric  discharge).  Certain  bacteria  can  bring  about 
a  similar  separation  at  ordinary  temperatures.  These  organisms  exist  in 
the  roots  of  leguminous  plants,  hence  these  plants  have  the  power  of 
taking  up  atmospheric  nitrogen  to  produce  the  proteids  (nitrification 
bacteria),  while  other  plants  and  all  animals  cannot  assimilate  atmos- 
pheric nitrogen.  Pure  cultures  of  these  bacilli  are  used  as  nitragin  to 
inoculate  fields  planted  with  leguminous  plants,  as  the  above  bacteria 
are  not  universally  distributed. 

Detection.  Only  by  the  absence  of  all  properties  characteristic  of 
other  gases. 

a.  Compounds  with  Hydrogen. 

Ammonia,  NH3. 

Hydroxy lamine,  NH2(0H). 

Hydrazine,  NgH^. 

Hydrazoic  acid,  N3H. 
Ammonia,  NHg.  Occurrence.  Combined  with  acids  to  a  slight 
extent  in  the  air,  in  rain-water,  in  the  soil,  and  also  in  many  spring- 
waters.  Ammonium  salts  (p.  150)  are  found  in  the  gases  of  volcanoes, 
in  carnallite,  in  guano  and  ammonium  sulphate  forms  the  mineral  mas- 
cagine. 


148    *  INORGANIC  CHEMISTRY, 

Formation.  Ammonium  nitrite  and  nitrate  are  produced  by  the 
action  of  the  electric  spark  upon  moist  air,  and  in  the  evaporation  of 
water  and  in  every  combustion  in  the  air:   2H2O+2N  =NH4N02. 

Nitrogen  and  hydrogen  combine  to  form  ammonia  only  with  the 
dark  electric  discharge;  nevertheless,  they  combine  in  the  nascent 
state:  thus  when  zinc  is  dissolved  in  5  to  6  per  cent,  nitric  acid 
(p.  160).  In  this  process  no  hydrogen  is  generated,  but  the  hydro- 
gen atoms  act  upon  the  nitric  acid  and  reduce  it  to  nitrogen,  which 
combines  with  the  hydrogen,  forming  ammonia:  SZn+GHNOg^ 
3Zn(N03)2+6H;  2HNO3+10H  =  6H2O+2N;  2N  +  6H=2NH3.  This 
reduction  of  nitric  acid  in  watery  solution  can  be  done  more  readily 
by  finely  powdered  aluminium,  zinc,  or  iron  in  the  presence  of  strong 
bases  (p.  160). 

Ammonia  is  formed  in  a  similar  manner  in  the  putrefaction  of 
organic  nitrogenous  substances,  or  by  heating  them  in  the  absence 
of  air  (in  their  dry  distillation),  or  by  fusing  them  with  strong  bases, 
or  on  heating  them  with  concentrated  sulphuric  acid,  when  the  nascent 
nitrogen  and  hydrogen  unite  (see  Elementary  Analysis). 

In  the  past,  ammonium  chloride,  a  salt  of  a-mmonia,  used  to  be  ob- 
tained by  the  dry  distillation  of  camel-dung  in  the  oasis  of  Jupiter  Ammon, 
hence  the  name,  sal  ammoniacum. 

Preparation.  Ammonia  is  chiefly  prepared  by  heating  ammonium 
salts  with  stronger  bases  such  as  KOH,  NaOH  or  cheaper  with  cal- 
cium hydroxide,  Ca(0H)2: 

(NH,),S04+  Ca(0H)2  =  CaS04+  2H2O+  2NH3. 

Ammonium         Calcium        Calcium 
sulphate  hydroxide,    sulphate. 

The  starting-point  in  this  preparation  is  the  ammonia  obtained 
as  a  by-product  in  the  dry  distillation  of  coal  (coke  and  gas  manu- 
facture). Coal  contains  about  1.5  per  cent,  nitrogen  which  on  heating, 
in  great  part,  combines  with  the  hydrogen  which  is  also  present, 
forming  ammonia.  On  passing  the  generated  gases  (illuminating- 
gases)  through  water,  the  ammonia  is  absorbed,  the  solution  (ammo- 
niacal  liquor)  is  neutralized  with  sulphuric  acid:  2NH3+H2S04  = 
(NH4)2S04  (p.  150),  and  evaporated  to  dryness.  The  ammonium 
sulphate  which  remains  is  purified  by  subUmation  and  then  decom- 
posed by  heating  with  calcium  hydroxide. 


NITROGEN.  149 

Properties.  Colorless  gas  having  when  moist  an  alkaline  reaction 
and  whose  pecuhar  odor  may  be  detected  in  the  smallest  quantity; 
it  is  0.59  times  hghter  than  air  and  must  be  collected  over  mercury, 
as  one  volume  of  water  at  0°  dissolves  1148  volumes  ( =0.875  parts  by 
weight)  of  the  gas  and  at  20°  739  volumes  (  =0.526  parts  by  weight). 
At  —34°  it  Uquefies  to  a  colorless  hquid,  which  solidifies  at -75°. 
Liquid  ammonia  boils  at  —34°  and  absorbs  considerable  heat  on 
evaporation.  This  is  made  use  of  in  the  production  of  artificial  ice  and 
cold,  as  it  may  be  Hquefied  at  10°  by  a  pressure  of  7  atmospheres. 

It  is  a  body  having  very  great  activity,  as  it  has  powerful  action 
upon  many  metalloids  and  metals,  on  the  latter  especially  in  the 
presence  of  air  and  water.  On  passing  dry  ammonia  over  heated 
potassium,  potassium  nitride  is  produced:  SK+NHg  =NK3-f3H; 
over  heated  magnesium,  magnesium  nitride  is  obtained :  3Mg+  2NH3  = 
Mg3N,+  6H. 

Ammonia  does  not  burn  in  the  air,  but  it  burns,  on  the  contrary, 
in  pure  oxygen  with  a  yellowish  flame,  forming  water  and  nitrogen; 
oxygen  may  also  be  made  to  burn  in  ammonia  (p.  109) :  2NHg+  30  = 
3HjO+2N. 

Chlorine  gas  inflames  in  ammonia  gas  with  the  formation  of  white 
vapors  of  ammonium  chloride  (p.  146). 

When  mixed  with  oxygen  and  passed  over  heated  spongy  platinum 
it  is  converted  into  nitric  acid:  NH3+4O  =HN03+H20. 

Hypochlorites  or  hypobromites,  for  instance  solutions  of  chloride 
of  lime  or  sodium  hypobromite,  decompose  ammonia,  setting  free  all 
the  nitrogen  (p.  147). 

Caustic  ammonia  is  the  name  given  to  the  watery  solution  of 
ammonia,  whose  specific  gravity  is  less  according  to  the  amount  of 
ammonia  it  contains.  It  has  the  odor  of  ammonia  and  an  alkaline 
reaction,  and  precipitates  the  heavy  metals  as  hydroxides  from  their 
solutions :  FeS04+  2NH3+  2Yi,0  =  Fe(0H)2+  (NHJ^SO^.  It  behaves, 
therefore,  as  a  strong  base  and  may  be  considered  as  a  watery  solution 
of  NH4-OH  (corresponding  to  K-QH).  This  compound  is  indeed 
not  known  free,  but  organic  derivatives  of  the  same,  the  so-called 
ammonium  bases  (see  Part  III),  which  behave  Uke  aqueous  solutions 
of  the  bases  KOH  or  NaOH.  Caustic  ammonia  having  a  specific 
gravity  0.96  contains  10  per  cent,  by  weight,  and  is  ordinarily  ob- 
tained by  diluting  the  commercial  caustic  ammonia  with  water. 


150  INORGANIC  CHEMISTRY. 

Commercial  ammonia  has  a  specific  gravity  0.90  and  contains  28 
per  cent  NH,. 

Salts  of  Ammonia.  Moist  gaseous  ammonia,  as  well  as  its  solution, 
has  strong  basic  properties  and  yields  salts  with  acids  by  direct  addi- 
tion; these  salts  have  great  similarity  to  the  alkali  salts,  therefore 
they  will  be  treated  of  in  connection  with  these. 

NHj  +  HCl     =  NH4CI  Ammonium  chloride ; 

2NH3  +  H2SO4  =  (NH4)  2SO4  Ammonium  sulphate ; 

NHa-fHjS     =(NH4)HS  Ammonium  hydrosulphide; 

2NH3+H2S      =(NH4)2S  Ammonium  sulphide. 

In  the  ammonia  compounds,  the  group  NH4  behaves  like  a  uni- 
valent metal,  in  that  it  replaces  the  hydrogen  of  acids  with  the  forma- 
tion of  salts;  This  group  NH4  is,  therefore,  called  ammonium,  and 
the  salts  of  ammonia  are  called  ammonium  salts. 

Detection.  1.  Free  ammonia  is  readily  detected  by  its  odor,  as 
well  as  by  the  brown  coloration  produced  on  turmeric  paper  and  the 
blue  color  produced  upon  moist  red  litmus  paper,  when  introduced  in 
an  atmosphere  containing  ammonia  gas.  On  allowing  the  paper  to  be 
exposed  to  air,  the  original  color  returns,  due  to  the  evaporation  of 
the  ammonia. 

2.  A  glass  rod  moistened  with  hydrochloric  acid  forms  visible 
vapors  of  ammonium  chloride  when  introduced  in  an  atmosphere 
containing  ammonia. 

3.  The  merest  traces  of  ammonia  in  watery  solution  can  be  de- 
tected by  the  brown  coloration  or  precipitation  produced  by  Nessler's 
reagent  (see  this). 

4.  In  regard  to  the  detection  of  ammonia  in  its  compounds  see 
ammonium  salts. 

Hydro xylamine,  Oxyammonia,  NHaCOH),  may  be  considered  as 
NHg,  in  which  one  atom  of  hydrogen  is  replaced  by  the  univalent  hy- 
droxyl  group,  OH. 

Preparation.  It  is  produced  by  the  action  of  dilute  nitric  acid  upon 
tin  (p.  160):  HN03  +  6H  =  NH2(OH)+2H20,  or  by  the  decomposition 
of  mercury  fulminate  (see  this)  by  HCl,  and  is  obtained  from  its  salts  by 
decomposition  by  bases.  Hydroxylamine  sulphate  is  obtained  from 
the  potassium  hydroxylamine  disulphonate,  produced  by  the  action  of 
alkali  bisulphites  upon  potassium  nitrite,  by  heating  with  water:  2KHS0, 
+KN02=KOH  +  N(S03K)2(OH).  .  ' 

Properties.  It  forms  explosive,  colorless,  deliquescent  crystals, 
which  melt  at  33°,  and  which  boil  at  58°  at  a  pressure  of  20  mm.     It 


NITROGEN.  151 

is  Tnthout  odor,  combustible,  readily  soluble  in  water,  having  a  strong 
reducing  action  and  is  a  weak  base.  With  the  aldehydes  it  fonns  oximes 
(see  these). 

H^droxylamine  salts  are  produced  by  the  direct  union  of  a  hydroxyl- 
amine  molecule  with  one  hydrogen  of  the  acid.  Hydroxylamine  chloride, 
NH2(0H)HC1,  forms  colorless,  poisonous  crystals,  which  are  readily  soluble 
and  which  have  a  reducing  action  but  not  explosive. 

Hydrazine,  Diamid,  Hg^^NHg.  Preparation.  By  the  action  of 
sulphur  dioxide  upon  potassium  nitrite  (KNOg)  we  obtain  nitric  Oxide- 
potassiim  sulphite,  KgSOg-N^Oj,  which  yields  hydrazine  when  treated 
m  aqueous  solution  with  nascent  hydrogen  (sodium  amalgam); 
KjSOg-Np^  +  SH  =N2H,  +  K,SO^  +  H20.  On  fractional  distillation  of 
the  solution  we  olDtain  hydrazine  hydrate,  NgH.-HjO,  which  yields  anhy- 
drous hydrazine  by  distilling  in  a  vacuum  with  barium  oxide. 

Properties.  Caustic,  basic  liquid  having  a  peculiar  odor,  volatile  at 
ordinary  temperatures  and  boiling  at  113°  and  forming  colorless  crystals 
at  1°  and  stable  even  at  300°.  Hydrazine  and  its  salts  have  a  strong 
reducing  power. 

Hydrazine  Salts.  Hydrazine  combines  with  acids  by  addition,  forming 
two  series  of  salts  which  we  may  consider  as  being  formed  by  the  bivalent 
radical  diammonium,  -H3N-NH3-,  replacing  2  H  atoms  of  the  acid 
thus:  N2H,  +  H2S04=  (NgHJSO,,  or  that  the  univalent  radical,  H,N-NH-, 
replaces  1  H  atom  of  the  acid,  thus:  H^N-NHI,  (H4N-NH2)S04;  these 
latter  salts  are  the  most  stable.  Diammonium  sulphate,  (N2Ha)2S04, 
separates  on  account  of  its  insolubility  from  solutions  of  all  the  other 
hydrazine  salts  by  treating  them   with  sulphuric  acid. 

Hydrazoic  Acid,  HN^     ^.    Preparation.     1.  An  ice-cold  solution  of 

nitrous  acid  (HNO,)  is  poured  into  an  ice-cold  solution  of  hydrazine: 
HNO2  +  N2H,  =  N3H  +  2H2O. 

2.  Ammonia  (NH3),  when  heated  with  metalhc  sodium,  yields  sodium 
amid,  NH2Na,  which  when  heated  with  nitrous  oxide,  NjO,  yields  the 
sodium  salt  of  hydrazoic  acid:  2NH2Na  +  N20=NaN3  +  NaOH  +  NH3. 
On  distilling  this  salt  with  dilute  sulphuric  acid,  we  obtain  an  aqueous 
solution  of  hydrazoic  acid. 

3.  By  the  action  of  a  solution  of  nitrogen  trichloride  in  benzol  (see 
opposite  page)  upon  hydrazine:  N2H4  +  NCl3=N3H+3HCl.  The  hydra- 
zoic acid  thus  obtained  can  be  made  anhydrous  by  careful  distillation 
and  treatment  with  calcium  chloride. 

Properties.  Colorless,  poisonous,  caustic,  strongly  acid  liquid,  boiling 
at  37°,  and  having  an  intolerable  odor.  With  glowing  bodies,  but  often 
also  spontaneously,  it  explodes  with  great  violence.  Miscible  with 
alcohol  and  water,  and  the  aqueous  solution  can  only  be  kept  with  safety; 
it  dissolves  all  metals  which  are  soluble  in  HCl. 

Hydrazoates,  or  azides,  are  similar  in  every  respect  to  the  salts  of  hydro- 
chloric acid  with  the  exception  that  they  all  readily  explode.  Silver 
nitrate  precipitates  white  silver  hydrazoate,  NgAg;  mercurous  nitrate 
precipitates  white  mercurous  hydrazoate,  NgHg. 


152  INORGANIC  CHEMISTRY, 

b.  Compounds  with  the  Halogens. 
Nitrogen  Chloride,  NCI3.  Preparation.  If  chlorine  is  passed  in 
a  saturated  ammonia  solution,  ammonium  chloride  and  nitrogen  are 
evolved  (p.  146).  If,  on  the  contrary,  chlorine  is  passed  in  excess, 
then  the  ammonium  chloride  is  still  further  decomposed  with  the 
formation  of  nitrogen  chloride: 

NH,Cl+6Cl  =  NCl3+4HCl. 

Properties.  Nitrogen  chloride  is  a  thick,  pale-yellow  liquid  having 
an  irritating  odor  and  a  specific  gravity  of  1.7,  which  on  shaking,  warm- 
ing, or  in  contact  with  many  bodies,  especially  of  organic  kind,  decom- 
poses into  its  constituents.  NCI3  is  rather  soluble  in  water,  and 
this  solution  often  spontaneously  decomposes  with  explosive  violence 
on  standing  with  the  generation  of  nitrogen;  the  solution  in  carbon 
disulphide,  chloroform,  benzol,  etc.,  is,  on  the  contrary,  rather  stable 
and  may  be  handled  with  safety. 

Nitrogen  bromide,  NBr3,  is  quite  similar  to  the  above. 

Nitrogen  iodide,  NI3  or  NHI^,  NHJ,  N2H3I3  =  (NH3+ NI3)  are 
produced  by  the  action  of  considerable  iodine  upon  ammonia  solutions 
according  to  conditions.  They  form  black  powders  which  violently 
explode.  Triazoiodide,  N3I,  is  produced  from  iodine  and  NgAg  (see 
Hydrazoates)  as  colorless  crystals  which  are  extremely  explosive. 

c.  Mixture  of  Nitrogen  and  Oxygen. 

Atmosplieric  Air.  The  air  consists  of  78.1  volumes  per  cent,  of 
nitrogen,  0.9  volume  per  cent,  of  argon,  and  21  volumes  per  cent,  of 
oxygen,  or  75.5  per  cent,  by  weight  of  nitrogen,  1.3  per  cent,  by  weight 
of  argon,  and  23.2  per  cent,  by  weight  of  oxygen.  Besides  these,  the  air 
always  contains  some  vapor  of  water,  carbon  dioxide,  traces  of  ammo- 
nia, hydrogen,  nitrous  and  nitric  acid,  as  well  as  the  elements  helium, 
krypton,  neon,  and  xenon,  and  where  considerable  coal  is  burnt  we 
also  have  sulphurous  and  sulphuric  acids.  The  air  also  contains 
numerous  microorganisms  which  cause  fermentation,  putrefaction, 
and  many  diseases. 

Properties.  Air,  especially  when  dry,  is  a  poor  conductor  of 
heat  and  electricity;  one  hter  of  dry  air  weighs  at  0°  and  760  mm. 
pressure  1.293  grams;  the  air  is,  therefore,  773.4  times  Hghter  than 
water.  Its  density  relative  to  02  =  32  (i.e.,  its  molecular  weight  if  it 
were  a  compound)  is  28.95.    The  air  is  liquefiable  at  — 191°,  forming  a 


NITROGEN.  153 

colorless  liquid  having  a  specific  gravity  of  0.995  (p.  41).  The  air  is 
very  readily  Uquefied  by  the  use  of  the  apparatus  as  suggested  by 
Linde  and  by  Hampton,  and  is  extensively  used  for  technical 
purposes. 

Nearly  all  liquid  and  gaseous  bodies  become  solid  when  cooled  in 
liquid  air,  and  chemical  transformations  are  retarded  or  arrested  at 
these  temperatures. 

In  regard  to  the  calculation  of  the  specific  gravity  of  gases  from 
their  molecular  weights  using  air  as  unit  see  p.  44. 

The  proportion  of  nitrogen  and  oxygen  in  the  air  is  nearly  un- 
changeable; still  the  air  is  to  be  considered  as  a  mixture  of  these 
gases  for  the  following  reasons: 

1.  If  oxygen  and  nitrogen  are  mixed  in  the  proportion  that  they 
exist  in  air,  and  the  electric  spark  is  passed  through  the  mixture,  we 
find  no  temperature  or  volume  changes,  and  the  mixture  shows  the 
same  properties  as  before,  namely,  the  properties  of  the  air. 

2.  The  proportion  by  weight  between  oxygen  and  nitrogen  in 
the  air  does  not  correspond  to  their  atomic  weights. 

3.  If  the  air  were  a  chemical  combination,  then  its  composition 
must  be  retained  when  it  is  dissolved  in  water.  If  air  is  shaken 
with  water,  more  oxygen  dissolves  than  nitrogen ;  if  the  air  is  expelled 
by  boiling  and  its  composition  determined,  we  find  that  it  consists 
of  35  volumes  per  cent,  oxygen  (important  for  aquatic  animals). 

4.  Liquid  air  yields  first  nearly  all  of  its  nitrogen  on  evaporation 
in  open  vessels  (p.  107). 

The  composition  of  the  air  is  the  same  because  of  the  diffusion  of 
the  gases  (p.  46). 

Considerable  oxygen  is  removed  from  the  air  by  the  processes  of 
respiration,  combustion,  putrefaction,  decay,  and  returns  to  the  air  as 
carbon  dioxide,  but  the  green  parts  of  the  plant  absorb  this  carbon  dioxide 
and  decompose  it  with  the  evolution  of  free  oxygen,  the  carbon  going  to 
form  the  structure  of  the  plant. 

The  amount  of  carbon  dioxide  in  the  air  amounts  on  an  average 
to  0.04  volume  per  cent.,  but  may  rise  to  1  or  2  per  cent,  in  rooms 
occupied  by  many  persons,  or  by  the  burning  of  many  gas-flames; 
experience  has  shown  that  it  is  not  advisable  to  have  more  than  0.1 
volume  per  cent,  in  a  room  for  habitation.  The  purity  of  the  air  can 
be  determined  by  estimating  the  amount  of  carbon  dioxide  contained 
therein. 


154  INORGANIC  CHEMISTRY, 

The  vapor  of  water  in  the  air  (humidity)  is  dependent  upon  the 
temperature  of  the  air  and  corresponds  nearly  to  the  vapor  tension 
of  the  water  in  milhmeters  at  tliis  temperature  (p.  115).  1000  hters  of 
air  saturated  with  vapor  of  water  contain  at  — 10°  2.4  grams  water, 
at  0°  4.9  g.  water,  at  +  20°  17.2  g.  water,  at  +  40°  55  g.  water. 

Ordinarily  the  vapor  of  water  amounts  to  only  from  50  to  70  per 
cent,  of  the  quantity  which  is  necessary  completely  to  saturate  the 
air;  if  the  quantity  is  greater,  then  the  air  appears  close  and  damp; 
when  less,  it  is  dry. 

1.  Determination  of  Nitrogen  and  Oxygen,  a.  According  to  volume, 
by  taking  a  certain  volume  of  air,  placing  it  in  a  tube  closed  at  one  end 
and  graduated  in  millimeters  (eudiometer),  placing  it  over  mercury,  and 
adding  a  certain  amount  of  hydrogen.  If  an  electric  spark  is  passed 
between  two  platinum  wires  placed  in  the  upper  part  of  the  tube,  an 
explosion  takes  place  and  water  is  formed,  and  the  volume  of  the  gases 
diminishes  on  the  cooling  of  the  same.  As  example,  100  volumes  of 
air  +  50  volumes  of  hydrogen  on  explosion  leave  87  volumes  of  gas. 
Hence  63  volumes  of  gas  have  been  condensed  into  water,  and  the  third 
o  this  =21  volumes  is  the  quantity  of  oxygen  contained  in  the  100 
volumes  of  air. 

h.  A  measured  volume  of  air  is  passed  over  a  weighed  amount  of  copper 
heated  to  red  heat,  and  the  increase  of  weight  determined  (  =  the  oxygen), 
and  the  volume  of  nitrogen  remaining  also  measured. 

2.  Determination  of  Vapor  of  Water,  a.  Physically  by  the  hygrometer 
or  psychrometer. 

b.  Chemically,  at  the  same  time  as  the  carbon  dioxide,  by  passing 
a  known  volume  of  air  through  weighed  calcium  chloride  tubes,  and 
then  through  tubes  filled  with  potassium  hydroxide.  The  increase 
in  weight  of  the  calcium  chloride  tubes  gives  the  amount  of  water  in 
the  volume  of  air  passed  through ;  the  increase  in  weight  of  the  potassium 
hydroxide  tubes  gives  the  carbon  dioxide. 

3.  Determination  of  Carbon  Dioxide,     a.  See  above,  2  b. 

b.  A  large  glass  vessel  whose  volume  has  been  carefully  determined 
is  filled  with  the  air  to  be  tested  and  a  measured  quantity  of  barium 
hydroxide  solution  added,  the  vessel  tightly  stoppered  and  shaken.  All 
the  carbon  dioxide  is  absorbed  and  is  precipitated  as  insoluble  barium  car- 
bonate: Ba(OH)2  +  C02=BaC03-fH20.  The  quantity  of  barium  hy- 
droxide contained  in  the  solution  is,  after  the  experiment, 'less  than  before 
and  the  quantity  of  carbon  dioxide  is  determined  by  the  difference. 


d.  Compounds 

with  Oxygen. 

Nitrous  oxide,           NgO. 

Hyponitrous  acid,  HNO. 

Nitric  oxide,              NO. 

— 

Nitrogen  trioxide,     NgOy 

Nitrous  acid,           HNOg. 

Nitrogen  dioxide,      NO^ 

— 

Nitrogen  tetroxide,   NgO^. 

— 

Nitrogen  pentoxide,  NjOj. 

Nitric  acid,               HNO,. 

NITROGEN.  155 

Oxygen  combines  directly  with  nitrogen  only  when  the  electric  spark 
is  passed  for  a  long  time  through  a  dry  mixture  of  these  gases.  Red 
nitrogen  dioxide  gas,  NOg,  is  in  part  produced.  If  water  is  present, 
ammonium  nitrite  is  produced  (p.  148). 

Nitrous  Oxide,  Laughing-gas,  N^  or  0<(^^^.     Preparation.    It  is 

produced  in  addition  to  nitric  oxide  by  the  action  of  15  to  18  per 
cent,  nitric  acid  upon  zinc  or  tin  (see  p.  160):  4Zn+10HNO5  = 
4Zn(N03)2+5H20+N20.  It  is  obtained  pure  by  heating  ammonium 
nitrate :   NH4NO3  =  N^OH-  2H2O. 

Properties.  Colorless  and  odorless,  neutral  gas,  1.52  times  heavier 
than  air,  with  a  sweetish  taste;  it  Hquefies  at  -88°,  forming  a  colorless 
liquid  which  sohdifies  to  an  ice-Uke  mass  at  — 103°.  Glowing  carbon  or 
ignited  phosphorus  burns  in  nitrous  oxide  the  same  as  in  oxygen 
gas;  feebly  burning  sulphur  is  extinguished,  as  there  is  not  sufficient 
heat  generated  to  decompose  the  gases  into  N2+O.  With  an  equal 
volume  of  hydrogen  it  explodes  when  ignited:  N20+2H  =  H20+2N; 
it  does  not  combine  with  oxygen.  One  volume  of  water  dissolves 
at  10°  1.1  volumes  of  this  gas;  on  account  of  this  property  and  because 
it  does  not  yield  red  nitrogen  dioxide  with  nitric  oxide,  it  can  be 
readily  differentiated  from  oxygen.  When  nitrous  oxide  is  inspired 
it  produces  insensibility,  and  on  account  of  the  condition  thus  pro- 
duced it  has  been  called  laughing-gas. 

If  metallic  sodium  is  heated  with  an  enclosed  volume  of  nitrous  oxide, 
it  burns  into  sodium  oxide,  and  a  volume  of  pure  nitrogen  remains  corre- 
sponding to  the  volume  of  NjO  used.  As  2  volumes  of  nitrous  oxide 
weigh  44  parts  by  weight,  and  2  volumes  of  nitrogen  =  28  parts  by  weight, 
then  the  combined  oxygen  must  weigh  16=1  volume,  and  hence  nitrous 
oxide  must  have  the  formula  N2O. 

Hyponitrous  Acid,  Nitrosyhc  Acid,  HNO,  more  correctly  HjNjOg  or 
HO-N=N-OH.  It  is  not  produced  from  NaP  +  HgO,  but,  on  the 
contrary,  decomposes  into  these  (see  below).  It  is  obtained  in  solution 
by  the  action  of  nitrous  acid  upon  hydroxy  lamina :  HN02  +  NH20H  = 
2HNO4-H2O,  and  in  the  anhydrous  form  by  treating  silver  hyponitrite, 
Ag2(N0)2  (see  below),  with  a  solution  of  HCl  in  ether,  when  Ag2(N0)2 
decomposes  into  AgCl  and  free  H2N2O2.  The  liquid  obtained  on  the 
evaporation  of  the  ether  is  readily  explosive,  thick,  and  solidifies  on 
cooling  into  colorless  crystals. 

Hyponitrites  are  produced  by  the  action  of  potassium  amalgam 
upon  the  aqueous  solutions  of  the  nitrate  or  nitrite;  by  precipitating 
the  alkali  salts  with  silver  nitrate  we  obtain  pale-yellow  silver  hypo- 
nitrite.  On  decomposing  the  salts  with  sulphuric  acid,  the  hyponitrous 
acid  set  free  immediately  decomposes  in  part  into  H-O  +  NjO  and  in 
part  according  to  the  equation  3H2N202=2N203  +  2NH,. 


156  INORGANIC  CHEMISTRY, 

Nitric  Oxide,  NO.  Preparation.  By  the  action  of  30  to  35  per  cent, 
nitric  acid  (p.  160)  upon  copper,  mercury,  silver,  and  many  other 
metals:    3CU+8HNO3  =3Cu(N03),+  4H20+2NO. 

Properties.  Colorless,  neutral  gas,  1.04  times  heavier  than  air, 
liquefiable  to  a  colorless  liquid  at  —154°.  It  is  decomposed  into 
nitrogen  and  oxygen  by  burning  substances,  but  it  requires  a  higher 
temperature  than  nitrous  oxide;  burning  sulphur,  ignited  carbon 
or  wood,  are  extinguished  therein,  while  burning  magnesium  or  ignited 
phosphorus  burns  brightly  in  this  gas.  When  mixed  with  hydrogen, 
nitric  oxide  burns  on  ignition  without  explosion:  NO+Hj  =H^O+N; 
with  carbon  disulphide  it  burns  with  an  intense  blue  flame  which  is 
very  rich  in  chemical  rays:  CS2+6NO  =  C02+2S02+6N.  It  is 
slightly  soluble  in  water  (^V  volume),  but,  on  the  contrary,  is  solu- 
ble in  an  aqueous  solution  of  ferrous  salts,  producing  a  brown  solution; 
on  warming  this  solution,  it  is  driven  off  (method  of  purification). 

Nitric  oxide  differs  from  all  other  gases  by  the  fact  that  with  the 
air  or  in  the  presence  of  oxygen  it  forms  brownish-yellow  nitrogen 
dioxide  gas;  hence  traces  of  free  oxygen  in  gaseous  mixtures  can  be 
determined  by  this  brownish-yellow  coloration. 

On  heating  sodium  in  a  closed  volume  NO,  one-half  of  the  volume 
of  gas  used  remains  as  nitrogen ;  hence  the  formula  for  this  gas  can  be 
derived  in  the  same  way  as  that  for  nitrous  oxide. 

Nitrogen  Trioxide,  Nitrous  Anhydride,  N^Og.  Preparation.  1. 
Equal  volumes  of  nitric  oxide  and  nitrogen  dioxide  or  4  volumes 
nitric  oxide  and  1  volume  of  oxygen  are  condensed  in  a  tube  cooled 
to  -21°. 

NO+NO^^NA-  2NO+0  =  N203- 

2.  By  the  distillation  of  arsenic  trioxide  with  nitric  acid  and 
cooling  the  vapors  produced  to  —21°. 

As  A+  2HNO3+  2H2O  =  2H3ASO4+  N0+  NOj. 

3.  By  mixing  a  sodium  nitrite  solution  with  sulphuric  acid  and 
coohng  the  dried  vapors  set  free  to  —21°  (see  Nitrites). 

Properties.  Deep-blue  hquid  at  —21°  which  gradually  decom- 
poses into  NO2+NO,  but  much  quicker  at  its  boihng-point  (3.5°). 
These  two  gases  on  cooling  unite  again,  producing  NjOjj*  hence  it 
only  exists  as  a  liquid. 


I 


NITROGEN,  157 

Sulphuric  acid  absorbs  NgOg,  respectively  NOg  +  NO,  with  the  forma- 
tion of  nitrosylsuphuric  acid  (lead  chamber  crystals,  p.  128). 

This  solution  of  nitrosylsulphuric  acid  in  sulphuric  acid  is  called 
nitrated  acid  and  when  undiluted,  is  very  stable. 

Nitrous  Acid,  HNO2  or  O^N~OH.  Occurrence.  As  ammonium 
nitrite,  NH4~N02  to  a  trivial  extent  in  the  air,  in  rain-water,  in  many 
spring-waters;  it  is  also  formed  to  a  slight  extent  on  the  evaporation 
of  water  in  the  air,  by  the  action  of  the  electric  spark  upon  moist 
air  (in  rain  after  thunder-storms),  in  all  combustion  processes  in  the 
air,  and  in  the  slow  oxidation  of  phosphorus  in  the  air,  on  rusting  of 
iron,  and  in  the  electrolysis  of  water  containing  air:  2N  +  2H20  = 
NH4-NO2.  It  occurs  as  nitrites  in  many  plant  juices,  nasal  mucus, 
and  saliva. 

Preparation  and  Properties.  Liquid  nitrogen  trioxide  mixes 
with  a  small  amount  of  ice-cold  water,  producing  a  blue  liquid,  which 
may  be  considered  as  HNO2  in  solution,  but  which  decomposes  at 
ordinary  temperatures  or  in  the  presence  of  considerable  water: 
3HNO2  =  HNO3+  2N0+  H,0. 

Nitrites  are  more  stable;  they  are  produced  by  saturating  the 
watery  solution  of  HNO2  with  bases,  oftener  by  carefully  heating 
the  corresponding  nitrate.  With  sulphuric  acid,  they  develop  red- 
dish-brown nitric  dioxide  gas  mixed  with  colorless  nitric  oxide 
gas,  as  the  sulphuric  acid  removes  the  water  from  the  nitrous  acid 
set  free:  2HN02  =  H20+NO-f-N02.  Weak  acids  set  nitrous  acid 
free,  but  this  decomposes  immediately  into  HNO3+2NO+H2O. 
Nitrous  acid  and  its  decomposition  products  have  an  oxidizing  action, 
therefore  bleach  plant  pigments  and  set  iodine  free  from  iodine  salts: 
2KI+2HN02  =  2KOH+2I-F2NO.  On  the  other  hand,  the  nitrites, 
on  account  of  their  tendency  to  be  converted  into  nitrates,  have  a 
reducing  action;  that  is,  they  decolorize  acidified  solutions  of  potas- 
sium permanganate :  5HNO2+  2KMn04+  3H2SO4  =  SHNOg-h  K2SO4+ 
2MnS04+3H20. 

Detection.  1.  The  aqueous  solution  of  nitrites  on  acidification  with 
sulphuric  acid  turns  starch  paste  and  potassium  iodide  blue. 

2.  Metaphenylendiamine  gives  an  intense  yellow  with  nitrite  solu- 
tions after  acidification. 

3.  Diphenylamine  gi\'es  the  same  reaction  as  with  nitric  acid. 


158  INORGANIC  CHEMISTRY. 

Nitrogen  Dioxide,  NO2.  Preparation.  1.  By  mixing  2  volumes 
of  nitric  oxide  and  1  volume  of  oxygen. 

2.  By  heating  lead  nitrate  and  cooling  the  vapors  produced: 
Pb(N03),  =  PbO+2N02+0. 

3.  By  passing  the  electric  spark  for  a  long  time  through  a  dry 
mixture  of  1  volume  of  nitrogen  and  2  volumes  of  oxygen  (p.  155). 

Properties.  Reddish-brown,  suffocating,  caustic,  and  poisonous 
gas  having  a  strong  oxidizing  action;  hence  it  sets  iodine  free  from 
iodine  compounds  and  supports  the  combustion  of  many  substances. 
It  is  1.5  times  heavier  than  air,  decomposes  with  water  into  nitric 
acid  and  nitric  oxide,  3N02+H20  =  2HN03+NO;  hence  it  used 
to  be  considered  as  an  acid  and  called  hyponitric  acid.  With  decreas- 
ing temperatures,  it  becomes  hghter  in  color,  when  its  volume  weight 
steadily  increases,  as  more  molecules  NO2  are  converted  into  N2O4 
and  condense  finally  into  pure 

Nitrogen  tetroxide,  N2O4,  which  at  0°  is  a  nearly  colorless  liquid, 
which  finally  soHdifies  at  -  20°  into  colorless  crystals,  which  melt  at 
— 10°.  Above  0°  the  liquid  becomes  more  and  more  yellow,  as  with 
the  increased  temperature  NO2  is  produced  and  at  26°  it  boils  and 
then  contains  20  per  cent.  NO2  (Dissociation). 

NgO,  is  the  mixed  anhydride  of  nitric  acid  and  nitrous  acid  (N20g  + 
N203=2N204),  as  it  forms  with  ice-cold  water  (or  with  bases),  nitric 
acid  and  blue  nitrous  acid  (or  their  salts):  N204  +  H20=HN03  +  HN02. 
With  water  at  ordinary  temperature  it  forms  nitric  acid  and  nitric  oxide, 
as  the  N2O4  is  first  split  into  2N02:3N02  +  H  0=2HN03  +  NO. 

Nitrogen  pentoxide,  nitric  anhydride,  NgOg,  is  obtained  by  passing 
dry  chlorine  gas  over  dried  silver  nitrate  at  60°;  2AgN03  +  2C1  =  2AgCl + 
NjC^  +  O,  or  by  distilling  nitric  acid  with  phosphorus  pentoxide: 
2HN03  +  P205=N205  +  2HP03.  The  phosphorus  pentoxide  removes  the 
elements  of  water  from  the  nitric  acid  and  is  converted  into  metaphos- 
phoric  acid  (HPO3),  which  is  not  volatile,  while  nitrogen  pentoxide  distils 
over  and  is  obtained  on  cooling  the  distillate  as  colorless  prismatic  crys- 
tals. These  melt  at  30°,  forming  a  yellow  liquid,  and  slowly  decompose 
at  a  slightly  higher  temperature ;  on  rapidly  heating,  as  well  as  by  keeping, 
it  decomposes  with  explosive  violence  into  nitrogen  dioxide  and  oxygen. 
With  water  it  forms  nitric  acid. 

Nitric  Acid,  HNO3  or  02N(0H).  Occurrence.  It  is  formed  to  a 
slight  extent  with  ammonium  nitrate  and  ammonium  nitrite  (p.  148) 
by  passing  the  electric  spark  through  moist  air;  otherwise  it  is  found, 
only  as  its  salts,  the  nitrates,  especially  sodium  nitrate  (Chili  salt 
peter,  NaNO,),  in  Peru  in  large  quantities.    It  is  also  found  as  potas 


NITROGEN.  159 

slum  nitrate  very  widely  diffused,  although  not  in  large  quantities, 
on  the  surface  of  the  earth,  especially  in  Egypt  and  India.  It  is 
found  as  calcium  nitrate,  Ca(N03)2,  or  so-called  wall  saltpeter,  on 
the  walls  of  stables  and  urinals.  ^Nitrates  are  formed  in  all  decomposi- 
tion processes  of  organic  nitrogenous  substances  (see  Nitrates) ;  also 
many  plants  contain  nitrates. 

Preparation.  By  distilling  alkali  nitrates,  chiefly  Chili  salt- 
peter, with  sulphuric  acid  at  a  temperature  not  above  220°: 

NaNOa  +  H,S04  =  NaHS04  +  HNOj. 

Sodium  nitrate.  Sodium  bisulphate. 

The  crude  nitric  acid  thus  obtained  contains  61-65  per  cent.  HNO3 
and  has  a  specific  gravity  of  1.36-1.40,  and  the  pure  nitric  acid  of 
commerce  is  obtained  from  this  by  redistillation  and  contains  68 
per  cent.  HNO3  (see  below). 

If,  in  the  distillation  the  temperature  rises  above  220°,  then  the 
sodium  bisulphate  decomposes  a  second  molecule  of  the  nitrate: 
NaHS04+NaN03  =  Na2S04+HN03;  the  temperature  in  this  case 
becomes  so  high  that  a  part  of  the  nitric  acid  decomposes,  2HNO3  =» 
H;,0+2N02+0,  and  red,  fuming  nitric  acid  is  obtained. 

Anhydrous  nitric  acid  is  obtained  by  distilling  pure  nitric  acid  with  con- 
centrated sulphuric  acid,  and  removing  the  nitrogen  oxides  produced 
by  passing  air  through  the  distillate. 

Properties.  Anhydrous  nitric  acid  is  a  colorless,  fuming  Uquid 
having  an  irritating  odor  and  a  specific  gravity  of  1.54,  forms  a  crys- 
talline solid  at  —40°,  and  begins  to  boil  at  86°  with  a  partial  decom- 
position into  H2O+2NO2+O,  and  miscible  with  water  in  all  propor- 
tions. If  dilute  nitric  acid  is  distilled,  the  boiling-point  gradually 
rises  until  it  is  121°  (p.  53),  when  nitric  acid  distils  over  which  con- 
tains 68  per  cent.  HNO3  ^^^  ^^s  a  specific  gravity  of  1.41.  Stronger 
nitric  acids  on  heating  give  off  HNO3  until  a  68  per  cent,  acid  is  pro- 
duced. 

Nitric  acid  vapors,  on  being  passed  through  a  red-hot  tube,  decom- 
pose into  nitrogen  dioxide,  water,  and  oxygen  (see  above);  this 
decomposition  takes  place  in  part  on  heating  and  on  standing  in  the 
sunlight;  hence  nitric  acid  gradually  becomes  yellow.  It  contains  76.1 
per  cent,  oxygen,  which  is  in  part  readily  given  off  to  oxidizable  bodies; 
hence  nitric  acid  is  one  of  the  strongest  oxidizing  agents  and  destroys 


160  INORGANIC  CHEMISTRY. 

organic  pigments  (indigo  solution)  and  other  organic  compounds,  or 
the  hydrogen  atoms  of  many  organic  compounds  may  be  replaced  by 
KO2  (nitration). 

Nitric  acid  is  also  called  aqua  fortis,  as  it  is  used  in  the  separation 
of  silver  from  gold.  It  dissolves  or  oxidizes  all  metals  with  the  excep- 
tion of  gold,  platinum,  rhodium,  iridium,  ruthenium,  and  oxidizes  all 
metalloids  with  the  exception  of  fluorine,  chlorine,  nitrogen,  and  the 
members  of  the  argon  group.  In  this  change  it  is  in  part  reduced 
to  nitrogen  oxides  (N2O,  -NO,  NO2),  and  indeed  higher  oxides  are 
produced  the  more  concentrated  the  acid  is.  Very  dilute  acid  is 
reduced  by  zinc  to  NH3,  and  by  tin  indeed  into  NH3  and  NH2(0H) 
(p.  150).  This  reduction  into  NH3  takes  place  still  more  readily  in 
alkahne  solution  (p.  148). 

With  6  per  cent,  nitric  acid  NH3  is  produced :  4Zn  +  9HN03=  4Zn(N03)2 
+  3H2O  +  NH3;  with  18  per  cent,  nitric  acid  NgO  is  produced:  4Zn  + 
10HNO3=4Zn(NO3)2  +  5H2O  +  N2O;  with  30  per  cent,  nitric  acid  NO  is 
obtained:  3Zn  +  8HN03=3Zn(N03)2  +  4H20  +  2NO;  and  with  stronger 
nitric  acid  NOg  is  produced. 

Red  fuming  nitric  acid  is  a  reddish-brown  liquid  which  gives 
off  red  vapors  in  the  air  and  has  a  specific  gravity  of  1.48  to  1.50. 
It  consists  of  a  solution  of  about  8  parts  nitrogen  dioxide  dissolved  in 
100  parts  68  per  cent,  nitric  acid.  It  has  a  still  stronger  oxidizing 
power  than  colorless  nitric  acid;  when  mixed  with  water  it  becomes 
first  blue,  then  green,  and  finally  colorless,  because  nitrous  acid  and 
then  nitric  acid  are  produced  from  the  nitrogen  dioxide.  When  this 
acid  acts  upon  combustible  materials  they  may  be  made  to  take  fire. 

Nitro-hydrochloric  acid,  aqua  regia,  is  the  name  given  to  a  strong 
oxidizing  mixture  of  3  parts  hydrochloric  acid  with  1  part  nitric  acid, 
because  it  dissolves  nearly  all  metals,  including  platinum  and  gold 
(called  the  king  of  metals  by  the  alchemists). 

This  action  takes  place  especially  on  heating  and  depends  upon  the 
formation  of   chlorine  and  the  following  compounds: 

HNO3  +  3HC1=  2C1  +  2H2O  +  NOCl  (nitrosylchloride). 

HNO3 + HCl  =  H2O  +  NO2CI  (nitrylchloride,  existence  questionable) . 

These  two  chlorine  compounds  may  be  considered  at  the  chloran- 
hydrides  of  nitric  acid  and  nitrous  acid. 

(Acid  chlorides,  acid  chloranhydrides  are  those  acids  whose  ~0H 
groups  are  entirely  or  in  part  replaced  by  CI). 


PHOSPHORUS.  161 

Nitrates  are  produced  where  organic  nitrogenous  substances  undergo 
decay  in  the  presence  of  stronger  bases  and  air.  It  has  been  shown 
that  in  alkahne  soils  certain  bacteria  accumulate,  which  have  the  prop- 
erty of  oxidizing  the  ammonia  produced  in  the  decay  into  nitric  acid 
(so-called  nitrification  germs) :  KOH+  NH3+  40  =  KNO3+  2H2O. 

These  conditions  for  nitric  acid  formation  are  present  in  nearly  all 
soils,  and  this  is  the  reason  why  soluble  nitrates  are  found  in  spring-water 
and  the  upper  layers  of  the  earth,  especially  in  the  neighborhood  of 
stables.  On  the  other  hand,  a  series  of  bacteria  are  known  which  can 
reduce  the  nitric  acid  formed  into  nitrous  acid,  ammonia,  and  indeed 
into  nitrogen.  These  so-called  saltpeter-destroyers  are  the  cause  of  the 
loss  of  nitrogen  in  the  decomposition  of  manure  on  the  manure-heap. 

Nitrates  are  nearly  soluble  in  water;  on  strongly  heating  the 
alkali  nitrates  are  decomposed  into  nitrites  with  the  setting  free  of 
oxygen;  the  other  nitrates  decompose  into  the  oxide  of  the  metal 
and  develop  NO2+O.  The  nitrates  are  also  strong  oxidizing  agents; 
placed  on  red-hot  carbon  they  all  explode.  By  nascent  hydrogen 
these  soluble  nitrates  are  reduced  to  nitrites  or  ammonia  (p.  148). 

Detection.  1.  Copper  is  dissolved  by  nitric  acid  with  the  pro- 
duction of  blue  copper  nitrate  and  the  development  of  red  nitrogen 
dioxide  fumes.  The  nitric  acid  is  first  set  free  from  the  nitrates 
by  the  addition  of  sulphuric  acid. 

2.  If  a  solution  of  nitric  acid  or  nitrates  is  mixed  with  concen- 
trated sulphuric  acid  and  a  cold  solution  of  ferrous  sulphate  floated 
thereon,  a  dark  ring  forms  between  the  two  solutions. 

The  nitric  acid  oxidizes  a  part  of  the  ferrous  sulphate  into  ferric 
sulphate,  and  nitric  oxide  is  formed,  which  gives  a  brown  color  with 
the   still  undecomposed  ferrous  sulphate  (p.  156): 

6FeS0,  +  3H2SO,  +  2HN03=  SFe^CSO,)  3 + 4H2O  -f  2N0. 

3.  A  colorless  solution  of  diphenylamine  in  sulphuric  acid  is  colored 
deep  blue  by  traces  of  nitric  acid,  and  also  by  NOg,  HNOg,  and  other 
oxidizing  substances. 

2.  Phosphorus. 

Atomic  weight  31=  P. 

Occurrence.  Only  in  the  form  of  phosphates,  that  is,  salts  of 
phosphoric  acid,  H3PO4.  These  occur  in  the  mineral  kingdom  espe- 
cially as  calcium  phosphate,  Ca3(P04)2;  in  many  varieties  of  rocks 


162  INORGANIC  CHEMISTRY. 

which  are  called  phosphate  rock  or  phosphorites,  as  well  as  in  the 
coprolites  and  certain  varieties  of  guano  (both  fossil  excrements); 
in  the  minerals  phosphorite  and  apatite,  Ca3(P04)2+CaClF,  vivianite, 
FejCPO*)^;  as  cerium  phosphate  in  monozite  sand;  as  aluminum  phos- 
phate in  wavelite,  turquois,  osteoliths,  etc.  Phosphorus  occurs  in 
the  plant  kingdom  not  only  as  the  widely  distributed  phosphates, 
but  also  as  a  constituent  of  the  proteids.  In  the  animal  kingdom 
calcium  phosphate,  CagCPOJa,  forms  two-thirds  of  the  dried  skeleton; 
also  in  the  nerve  substance,  in  the  yoke  of  the  egg,  urine,  brain,  and 
blood.  In  the  iron  industry  the  phosphorus  contained  in  certain  iron 
ores  collects  in  the  so-called  Thomas-slag  (which  see),  which  contains 
about  50  per  cent.  Ca3(P04)2.  Phosphorus  was  first  (1669)  obtained 
by  heating  evaporated  urine,  whereby  the  phosphates  contained 
therein  were  reduced  on  heating  to  a  red  heat  with  the  carbon  formed 
(see  below). 

Preparation.  1.  From  mineral  phosphates  or  bones.  These 
latter  are  first  purified  from  gelatine  and  fat;  they  are  then  burned, 
when  the  organic  substance  is  destroyed  and  the  inorganic  remains 
as  bone-ash,  which  contains  about  85  per  cent,  calcium  phosphate. 

a.  The  mineral  phosphates  or  bone-ash  are  treated  with  two- 
thirds  their  weight  of  sulphuric  acid,  when  insoluble  calcium  sulphate 
and  soluble  primary  calcium  phosphate  are  produced: 

Ca^l  ^^^+  2^  [SO^  =  2CaS04+  CaH^j  ]^g^ 

h.  The  primary  calcium  phosphate  is  decanted  from  the  pre- 
cipitate and  evaporated  to  sirupy  consistency,  mixed  with  charcoal 
powder,  dried,  and  heated  to  a  faint-red  heat;  in  this  process  the 
primary  calciima  phosphate  is  transformed  into  calcium  metaphos- 
phate  and  water  is  given  off: 

CaH,(P04)2  =  Ca(P03)2+  21i,0,  • 

c.  The  residue  after  heating  is  placed  in  clay  retorts  after  being 
mixed  with  sand  (SiOJ  and  heated  to  a  white  heat,  when  all  the 
phosphorus  contained  in  the  calcium  metaphosphate  is  set  free: 

Ca(P03)2+  SiO^-l-  5C  =  CaSi03+  P^^  SCO. 


PHOSPHORUS.  163 

2.  By  heating  mineral  phosphates  with  carbon  and  a  flux  in 
the  electric  oven. 

The  phosphorus  form  as  a  vapor,  which  is  condensed  by  passing 
it  into  water;  it  is  purified  by  redistillation,  and  then  melted 
under  water  and  generally  moulded  in  the  form  of  sticks  in  glass 
moulds. 

Properties.  Phosphorus  is  a  transparent,  crystalline,  faintly 
yellowish,  very  poisonous  body  which  is  brittle  when  cold,  and  at 
ordinary  temperatures  as  soft  as  wax  and  having  a  faint  garlic-hke 
odor  (see  below).  It  has  a  specific  gravity  of  1.83,  melts  at  44°,  boils 
at  288°,  and  then  forms  colorless  vapors  whose  vapor  density  is  62, 
from  which  it  follows  that  its  molecular  weight  is  124  (p.  21).  As  its 
atomic  weight  is  only  31,  then  the  phosphorus  molecule  in  the  vapor- 
ous state  must  consist  of  4  atoms. 

Phosphorus  is  insoluble  in  water,  slightly  soluble  in  ether  and 
alcohol,  readily  soluble  in  fatty  oils  {oleum  phosphoratum)  and  carbon 
disulphide.  On  evaporation  of  the  solution  (in  the  absence  of  air, 
as  it  will  inflame  otherwise)  we  obtain  the  phosphorus  in  regular 
rhombododecahedra;  it  shines  in  the  dark  {<p(^^,  light,  and  (p6po<;^ 
carry);  it  smokes  in  moist  air  (vapors  of  PjOs)  with  the  generation 
of  an  ozone  odor,  whereby  it  is  oxidized  and  forms  phosphorous 
acid  (H3PO3)  and  phosphoric  acid  (H3PO4),  and  at  the  same  time 
ammonium  nitrite,  ozone,  and  hydrogen  peroxide  are  formed.  Even 
at  45°  it  inflames  and  burns  with  a  dazzling  white  flame  into  phos- 
phorus pentoxide  (P2O5) ;  the  ignition  may  take  place  even  on  lying 
in  the  air  or  by  friction;  hence  it  must  be  kept  under  water  and 
should  be  cut  only  under  water.  It  must  also  be  kept  in  the  dark, 
as  in  light  and  under  water  it  becomes  covered  with  a  layer  of  phos- 
phorus suboxide,  P4O. 

It  is  oxidized  to  phosphoric  acid  (p.  167)  on  warming  with  nitric 
acid  or  aqua  regia,  and  with  caustic  alkalies  it  forms,  on  warming, 
PH3  besides  hypophosphorous  acid  (p.  165). 

Phosphorus  combines  with  the  halogens  even  at  ordinary  tem- 
peratures with  the  development  of  flame,  and  with  most  metals  on 
warming,  producing  phosphides.  It  has,  especially  when  finely 
divided,  a  strong  reducing  action  and  separates  many  metals  (or 
their  phosphides)  from  their  salt  solution;  hence  paper  moistened 
with  silver  nitrate  and  exposed  to  an  atmosphere  containing  traces 


164  INORGANIC  CHEMISTRY, 

of  phosphorus  turns  black,  due  to  the  formation  of  PAgj.  If  hydrogen 
is  passed  over  gently  heated  phosphorus,  the  gas  burns  with  a  pale- 
green  flame,  due  to  the  phosphorus  it  contains. 

Detection.  If  the  substance  which  is  to  be  tested  for  yellow 
phosphorus  is  placed  in  a  flask  which  is  connected  with  a  long  tube 
surrounded  with  cojd  water,  and  if  the  contents  of  the  flask  are  heated, 
then  the  phosphorus  volatilizes  with  the  steam  and  we  see  in  the 
dark  a  prominent  generally  ring-formed  light  where  the  vapor  con- 
denses. If  the  quantity  of  phosphorus  is  not  too  small,  small  masses 
of  phosphorus  may  be  found  in  the  condenser  (Mitscherlich's 
method). 

Red  Phosphorus  (Amorphous  Phosphorus) .  Preparation.  If  yel- 
ow  phosphorus  is  heated  in  closed  tubes  with  a  gas  that  has  no  action 
upon  it  (carbon  dioxide  or  nitrogen)  for  a  few  minutes  to  300°  or 
for  a  longer  time  to  at  least  250°,  then  it  is  converted  into  a  deep- 
red  modification  having  entirely  different  properties.  On  treatment 
with  carbon  disulphide  or  caustic  alkali  any  unchanged  yellow  phos- 
phorus present  may  be  removed. 

Properties.  Reddish-brown,  odorless  and  tasteless,  non-poison- 
ous, hexagonal  microcrystalline  powder  having  a  specific  gravity  of 
2.2,  insoluble  in  carbon  disulphide,  fatty  oils,  etc.,  does  not  shine  in 
the  dark,  does  not  change  in  the  air,  does  not  ignite  on  friction,  but 
first  at  260°,  and  combines  with  the  halogens  only  on  warming. 
It  slowly  vaporizes  without  decomposition  at  100°;  when  heated 
to  260°  in  a  gas  with  which  it  is  not  active  it  vaporizes  without 
previously  melting,  and  if  the  vapor  can  expand,  it  passes  over  again 
into  yellow  phosphorus. 

From  the  depression  of  the  freezing-point  (p.  20)  of  a  dilute  solution 
of  red  phosphorus  in  PBrg  it  follows  that  the  molecule  consists  of  eight 
or  more  atoms  of  P,  and  also  that  it  is  a  polymolecular  modification  of 
ordinary  phosphorus. 

The  low  chemical  energy  of  red  phosphorus  seems  to  be  dependent 
upon  the  diminished  motion  of  its  atom;  in  its  formation  from  yellow 
phosphorus  a  considerable  development  of  heat  takes  place,  hence  the  red 
phosphorus  contains  less  energy. 

Black  or  metallic  phosphorus  can  be  obtained  by  heating  ordinary  or 
red  phosphorus  in  vacuous  tubes  to  530°,  or  more  readily  on  heating  with 
lead,  whereby  the  phosphorus  dissolves  in  the  fused  lead  and  separates  on 
cooling  as  metallic-like,  dark  rhombohedra  which  have  a  specific  gravity 
of  2.34  and  are  even  less  active  than  red  phosphorus.  This  modification 
is  perhaps  only  better  crystalline  red  phosphorus. 


PHOSPHORUS.  165 

a.  Compounds  with  Hydrogen. 

Gaseous  phosphureted  hydrogen,  PH,. 
Liquid  phosphureted  hydrogen,  PjH^. 
Solid  phosphureted  hydrogen,        P^Hj. 

Gaseous  Phosphureted  Hydrogen,  Hydrogen  Phosphide,  Phos- 
phine,  PH,.  Preparation.  1.  Analogous  to  arseniureted  hydrogen, 
AsHj,  from  dilute  sulphuric  acid,  zinc,  and  phosphorus. 

2.  By  heating  phosphorous  acid  (H3PO3)  or  hypophosphorous 
acid  (H3PO2): 

4H3P03  =  PH3+3H3PO,  (phosphoric  acid); 

2H3P02=PH3+     H3PO4 

3.  By  decomposing  calcium  phosphide  with  water  or  dilute 
hydrochloric  acid:  Ca3P2+6HCl  =  3CaCl2+2PH3. 

4.  Ordinarily  by  boiling  phosphorus  with  alkali  hydroxide  solu- 
tion:  3KOH+4P+3H20  =  PH3+3KH2P02. 

5.  From  phosphonium  iodide  (see  below)  by  heating  with  alkali 
hydrate  solution :  PH J+  KOH  =  PH3+  KI+  HOH. 

Properties.  The  phosphureted  hydrogen  gas  obtained  according 
to  methods  1  to  4  always  contains  small  amounts  of  hydrogen  and 
liquid  phosphureted  hydrogen,  P2H4,  which  is  spontaneously  inflam- 
mable and  which  condenses  when  the  gas  is  passed  into  a  tube  sur- 
rounded by  an  ice  mixture,  or  is  decomposed  by  passing  the  gas 
through  hydrochloric  acid  or  alcohol.  Pure  PH3  is  a  colorless,  poison- 
ous, neutral  gas  which  is  insoluble  in  water,  has  a  garlic-like  odor,  and 
liquefies  at  —86°  and  solidifies  at  —134°.  It  does  not  inflame  spon- 
taneously, but  inflames  with  chlorine  and  bromine  vapors,  and  with 
oxidizing  agents  it  yields  spontaneously  inflammable  P2H4.  When 
ignited,  PH3  burns  into  water  and  phosphoric  anhydride  (P2O5), 
forming  a  white  smoke  which  often  forms  rings  that  rise.  In 
contradistinction  to  NH3  phosphureted  hydrogen  has  only  weak 
basic  properties,  as  it  unites  directly  only  with  HBr  and  HI,  form- 
ing so-called  phosphonium  compounds  for  instance  phosphonium 
iodide,  PHJ;  with  HCl  it  unites  only  at  —35°.  It  has  a  reducing 
action  and  hence  separates  the  pure  metal  or  the  metaUic  phosphide 
from  many  metallic  salt  solutions. 

If  the  electric  spark  is  passed  through  a  tube  filled  with  PH3,  amor- 
phous phosphorus  separates,  the  volume  of  the  gas  increases  one-half 


166  INORGANIC  CHEMISTRY. 

and  consists  of  pure  hydrogen:  2  vols.  PH3=34  parts  by  weight  give  3 
vols.  H  =  3  parts  by  weight,  the  phosphorus  separated  weighing  31  parts. 

Liquid  phosphuretted  hydrogen,  PgH^,  is  obtained  by  cooling  self-inflam- 
mable PHg,  which  forms  a  colorless,  refractive  liquid  insoluble  in  water, 
boiling  at  57°,  and  spontaneously  inflammable  in  the  air  and  burning 
to  P2O64-2H2O.  Its  presence  in  inflammable  gases  (marsh-gas),  etc., 
makes  these  spontaneously  inflammable,  and  this  is  the  reason  why  PH, 
when  it  has  not  been  passed  through  cool  tubes  inflames  spontaneously 
in  the  air. 

Solid  Phosphureted  Hydrogen,  P4H2.  Liquid  phosphureted  hydrogen 
in  contact  with. carbon,  sulphur,  concentrated  HCl,  or  by  sunlight,  de- 
composes into  gaseous  and  solid  phosphureted  hydrogen:  5P2H4= 
ePHg  +  P^Hj.  P4H2  is  also  obtained  by  dissolving  CagPj  in  warm  con- 
centrated sulphuric  acid.  It  is  a  yellow,  odorless,  and  tasteless  powder 
which  inflames  at  160°  or  by  shock  and  burning  into  2P2O5  +  H2O. 

6.  Compounds  with  the  Halogens. 

Phosphorus  Trichloride,  PCI3.  On  passing  dry  chlorine  over 
gently  warmed  phosphorus  it  inflames  and  forms  PCI3,  which  may 
be  collected  in  a  receiver.  It  is  a  colorless  liquid  which  boils  at  76° 
and  fumes  in  the  air,  as  it  decomposes  with  the  water  contained  in 
the  air  into  phosphorous  acid  and  hydrochloric  acid:  PClj-l-SHjO™ 
HsP03+3HCL 

Phosphorus  pentachloride,  PCI5,  is  obtained  by  the  action  of 
chlorine  upon  PCI3  as  a  crystalline,  yellowish  mass  which  vaporizes 
at  148°,  and  decomposes  with  considerable  water  into  phosphoric 
acid:  PCl5+4H20  =  H3P04+5HCl;  with  little  water  it  decomposes 
into  hydrochloric  acid  and 

Phosphorus  oxychloride,  POCI3,  a  colorless  fuming  liquid  which 
boils  at  107°:  PCl5+H20  =  POCl3+2HCl. 

Phosphorus  bromides  and  iodides  are  entirely  analogous  to  the 
chlorine  compounds.  They  are  obtained  by  bringing  together  the" 
constituents  in  the  proportion  represented  by  their  formulae. 

c.  Compounds  with  Oxygen. 

Phosphorus  monoxide,  PgO.  Hypophosphorous  acid,  HaPOj. 

Phosphorus  trioxide,      PjOg.  Phosphorous  acid,  H3PO3. 

f  Orthophosphoric  acid,  H3PO4. 

Phosphorus  pentoxide,  PaOg.  •  Metaphosphoric  acid,  HPO3. 

[  Pyrophosphoric  acid,  H^PjOj. 

Phosphorus  tetroxide,    PjO^.  Hypophosphoric  acid,  H^PgOj. 

Phosphorus  monoxide,  PgO,  obtained  from  H3PO3  with  PCI3,  is  a 
yellowish-red,  amorphous  body  which  does  not  combine  with  water 
and  alkalies:  2H,PO,+2PCl3=6HCl  +  P20,-i-P20. 


PHOSPHORUS  167 

Hypophosphorous  acid,  H3PO2,  is  produced  by  decomposing  barium 
hypophosphite  (p.  165,  4)  with  sulphuric  acid.  The  solution  obtained 
after  filtering  oil  the  barium  sulphate  is  concentrated  by  evaporation 
under  the  air-pump  receiver  and  forms  a  colorless,  sirupy  liquid  which 
solidifies  into  large  white  plates  at  0°: 

B^<S:p8:+H>so.=H:ro:+Baso,. 

On  warming,  it  decomposes  into  phosphorous  acid  and  PH3  (p.  165) ;  on 
taking  up  oxygen  it  is  readily  converted  into  phosphoric  acid  and  is,  there- 
fore, a  strong  reducing  agent.  It  reduces  sulphuric  acid  to  sulphur 
dioxide  and  even  into  sulphur  and  precipitates  gold  and  silver  from 
their  solutions,  etc.  Only  one  of  its  hydrogen  atoms  can  be  replaced  by 
metals;  it  is,  therefore,  a  monobasic  acid,  having  the  formula  H2P0(0H). 

Hypophosphites  are  produced  on  warming  an  aqueous  solution  of  the 
bases  with  phospliorus;  they  have  a  reducing  action  and  hence  are  readily 
converted  into  phosphates. 

Phosphorus  trioxide,  PgOg  (according  to  its  vapor  density,  phos- 
phorus hexoxide,  P40g,  formerly  erroneously  called  phosphorous  anhy- 
dride), is  produced  on  passing  a  slow  current  of  dned  air  over  gently 
heated  phosphorus  and  forms  a  volatile,  white  amorphous  powder  which 
is  readily  oxidized  into  P2O5  and  which  dissolves  in  water  with  the  separa- 
tion of  a  yellow  amorphous  powder  (perhaps  P^O).  On  heating  to  400°  it 
decomposes  into  phosphorus  and 

Phosphorus  tetroxide,  P2O4,  the  anhydride  of  hypophosphoric  acid, 
which  forms  colorless  needles. 

Hypophosphoric  acid,  H^PjOe,  is  only  known  in  aqueous  solution 
and  is  produced  when  moist  phosphorus  is  exposed  for  a  long  time  to  the 
air.  It  is  characterized  by  its  difficultly  soluble  acid  sodium  salt, 
NajHaPgOg,  which  is  used  in  the  separation  of  this  acid  from  the  phos- 
phorous acid  and  phosphoric  acid  produced  at  the  same  time. 

Phosphorous  acid,  H3PO3,  is  formed  beside  phosphoric  acid  and 
hypophosphoric  acid  in  the  slow  oxidation  of  phosphorus  in  moist  air, 
and  may  be  obtained  pure  by  decomposing  phosphorus  trichloride  with 
water:  PCl3  +  3H20=H3P03  +  3HCl.  If  the  solution  obtained  is  evap- 
orated under  the  air-pump  receiver,  phosphorous  acid  separates  in  color- 
less, deliquescent  crystals  which  melt  at  70°,  and  on  further  heating 
decompose  into  phosphoric  acid  and  PH3  (p.  165).  Analogous  to  H3PO2 
it  takes  up  oxygen  and  is  readily  converted  into  phosphoric  acid,  and 
hence  acts  like  a  very  strong  reducing  body.  Only  two  of  its  hydrogen 
atoms  can  be  replaced  by  metals,  therefore  it  is  a  bibasic  acid  having 
the  formula  HP0(0H)2. 

Phosphites  are  also  strong  reducing  agents,  but  are  not  oxidized  in 
the  air. 

Phosphorus  pentoxide,  phosphoric  anhydride,  P2O5,  is  produced 
when  phosphorus  is  burnt  in  a  strong  current  of  dry  oxygen  or  air 
It  forms  white,  neutral,  flocculent  masses  which  have  a  greenish 
phosphorescence  in  the  dark  and  which  readily  absorb  moisture  and 
deliquesce,  forming  metaphosphoric  acid  (process,  p.  168).     Because 


168  INORGANIC  CHEMISTRY, 

of  this  relationship  to  water  it  is  used  in  drying  gases,  as  well  as 
in  removing  water  from  many  substances. 

Orthophosphoric  Acid,  Phosphoric  Acid,  H3PO4  or  OP  (OH),. 
Occurrence.     See  Phosphorus. 

Preparation.  1.  On  dissolving  phosphorus  pentoxide  in  cold 
water  metaphosphoric  acid  (HPO,)  is  produced,  which,  on  boiling 
the  solution,  is  converted  into  orthophosphoric  acid : 

P  A+  H2O  =  2HPO3.        HPO3  +  Bfi  =  H3PO4. 

2.  By  treating  bone-ash  with  the  corresponding  quantity  of  sul- 
phuric acid  (p.  162)  and  evaporating  the  Hquid  obtained  on  decanta- 
tion  from  the  calcium  sulphate : 

Ca3(P04)2+  3H2SO4  =  3CaS04+  2H3PO4. 

3.  By  heating  phosphorus  or,  better,  amorphous  phosphorus 
with  nitric  acid;  this  gradually  dissolves  with  the  development 
of  red  vapors  of  the  oxides  of  nitrogen : 

3HNO3+  P  =  H3P0,+  2NO2+  NO. 

This  solution  is  evaporated  so  as  to  drive  off  the  excessive  nitric  acid, 
and  a  colorless  aqueous  solution  of  phosphoric  acid  is  obtained. 

Properties.  On  further  evaporation  of  the  aqueous  solution 
obtained  in  the  various  methods  of  preparation,  colorless,  rhombic 
crystals  which  melt  at  38°  and  which  deliquesce  in  the  air  separate 
out.  It  is  readily  soluble  in  water.  It  is  a  weaker  acid  than  sulphuric 
or  nitric  acid,  but  H3PO4  sets  these  acids  free  from  their  compounds 
on  heating,  because  it  is  less  volatile.  Commercial  phosphoric  acid 
is  a  25  per  cent,  watery  solution  having  a  specific  gravity  of  1.154. 

On  heating  H3PO4  it  loses  water  and  is  converted  into  pyrophos- 
phoric  acid  and  then  into  metaphosphoric  acid.  These  three  phos- 
phoric acids,  which  differ  from  each  other  very  markedly  in  composi- 
tion and  properties,  may  be  considered  as  combinations  of  PjOj 
with  3,  2,  and  1  molecule  water: 

P205+3H20  =  2H3P04,  orthophosphoric  acid; 
P2O5+  2H2O  =  H4P2O7,  pyrophosphoric  acid ; 
PPa-f  H20=2HP08,  metaphosphoric  acid. 


PHOSPHORUS.  169 

Phosphates.  Orthophosphoric  acid  forms  three  series  of  salts 
according  as  1,  2,  or  3  atoms  of  hydrogen  are  replaced  by  metals. 

The  phosphates  used  to  be  divided,  according  to  their  behavior  towards 
litmus,  into  acid  salts,  MH2PO4,  neutral  salts,  MgHPO^,  and  basic 
salts,  MgPO^.  According  to  the  present  view  of  salts,  the  compounds 
having  the  formula  MH2PO4  as  well  as  MjHPO^  may  be  considered  as 
acid  salts.  In  regard  to  the  nomenclature  of  such  salts  and  the  poly- 
basic  acids  see  p.   101. 

Detection.  1.  Orthophosphoric  acid  and  its  salts  give  a  yellow 
crystalline  precipitate  of  ammonium  phosphomolybdate,  I2M0O3+ 
(NH4)3P04+6H20,  when  their  solutions  are  treated  with  nitric  acid 
and  an  excess  of  ammonium  molybdate  solution. 

2.  Silver  nitrate  produces  a  yellow  precipitate  of  silver  phosphate, 
AggPOi,  in  neutral  phosphate  solutions. 

3.  A  solution  of  magnesium  salt  treated  with  ammonium  salts 
and  ammonia  (magnesia  mixture,  see  Magnesium,  c)  gives  a  white 
precipitate  of  ammonium  magnesium  phosphate,  Mg(NH4)P04+  6H2O, 
with  phosphate  solutions. 

Pyrophosphoric  Acid,  H4P2O7.  Preparation.  By  heating  orthopho^ 
phoric  acid  to  250'=-300°:    2E.^yO^=}i,^?^0^  +  E.^O. 

Properties.  White  crystalline  masses,  readily  soluble  in  water  and 
slowly  converted  into  orthophosphoric  acid  on  standing,  but  more  quickly 
on  heating. 

Detection.  Ammonium  molybdate  and  magpesia  mixture  give  a  pre- 
cipitate in  aqueous  solutions  only  when  a  transformation  into  H3PO4 
has  taken  place. 

Pyrophosphates  are  obtained  by  heating  the  secondary  phosphates 
to  a  red  heat:  2K2HP04=K4P207  +  H20-  They  are  stable  on  boiling 
their  watery  solution,  but  on  boiling  with  dilute  acids  they  are  trans- 
formed into  orthophosphates.  With  silver  nitrate  they  give  a  white 
precipitate  of  silver  pyrophosphate,  Ag4P207.  The  sodium  salt  readily 
dissolves  iron  salts  (removal  of  iron-stains  and  ink-spots  from  linen). 

Metaphosphoric  Acid,  HPO3.  Preparation.  1.  By  dissolving  phos- 
phoric acid  anhydride  in  cold  water. 

2.  By  continuously  heating  ortho-  or  pyrophosphoric  acid  until  no 
more  water  is  driven  off: 

H3P04=HP03  +  H20;  H4P207=2HP03  +  H20. 

Properties.  Colorless  transparent  masses  (glacial  phosphoric  acid) 
which  melt  on  heating,  volatilize  at  a  red  heat  (hence  free  phosphoric  acid 
is  not  used  in  the  preparation  of  phosphorus).  It  deliquesces  in  moist 
air,  dissolves  in  water,  and  on  standing  gradually  yields  orthophosphoric 
acid,  but  more  quickly  on  boiling. 

Detection.  It  differs  from  ortho-  and  pyrophosphoric  acid  by  its 
property  of  precipitating  proteid  solutions  (use  in  the  detection  of  proteids 


170  INORGANIC  CHEMISTRY, 

in  urine,  etc.)  and  by  being  precipitated  by  barium  chloride  solution. 
Magnesia  mixture  and  ammonium  molybdate  only  yield  a  precipitate 
in  aqueous  solution  when  a  transformation  into  orthophosphoric  acid 
has  taken  place. 

Metaphosphates  are  prepared  by  heating  the  primary  phosphates  to 
a  red  heat:  KH2P04=KP03  +  H20;  on  boiling  their  aqueous  solution 
they  are  converted  into  orthophosphates;  with  silver  nitrate  they  give 
a  white  precipitate  of  silver  metaphosphate,  AgPOg. 

d.  Compounds  with  Sulphur. 

Phosphorus  trisulphide,  PgSg,  and  phosphorus  pentasulphide,  PgSg, 
are  produced  by  carefully  melting  together  the  corresponding  weights 
of  sulphur  and  amorphous  phosphorus.  They  are  yellowish,  crystalline 
bodies  which  are  decomposed  by  water: 

P2S3  +  6HOH  =  2H3P03  +  3H2S; 
P2S5 + 8H0  H  =  2H3PO,  +  5H,S. 


3.  Arsenic. 

Atomic  weight  75  =As. 

Occurrence.  Arsenic  occurs  native  in  crystalline  masses  as  arsenic. 
Combined  it  occurs  as  orpiment,  AsgSg,  and  realgar,  As^S^,,  in  pyrargyrite 
and  tennanite  (p.  181)  as  arsenopyrite  or  mispickel,  FeSAs,  as  cobalt 
glance  or  cobaltite,  CoSAs,  as  smaltite,  C0AS2,  gersdorffite,  NiSAs, 
as  niccolite,  NiAs,  as  lollingite,  FeAsj,  and  as  arsenoUte,  AsjOg.  It 
occurs  in  small  quantities  in  many  ores,  coal,  shale,  in  sulphur,  etc. ; 
so  that  bodies  prepared  from  such  materials  contain  arsenic.  Arsenical 
mineral  springs  (Levico,  Roncegno)  are  also  known.  Many  alloys, 
such  as  speculum  metal,  brass,  lead  shot,  often  contain  arsenic. 

Preparation.  1.  By  heating  mispickel,  FeSAs,  in  earthenware 
tubes,  when  it  decomposes  into  iron  sulphide  and  arsenic;  this  latter 
vaporizes  and  is  passed  through  tubes,  where  it  condenses  in  crys- 
talline masses. 

2.  By  heating  arsenic  trioxide  (flowers  of  arsenic)  with  carbon: 
As203+3C  =  2As+3CO. 

Properties.  Grayish-white,  metallic-like,  shining,  opaque,  brittle, 
crystalline  masses,  sometimes  well  defined  rhombohedra,  having  a 
specific  gravity  of  5.7.  It  is  readily  oxidizable,  and  not  soluble  without 
change  in  any  solution,  is  extremely  poisonous,  as  well  as  its  com- 
pounds, and  on  heating  (in  the  absence  of  air  or  in  an  indifferent  gas) 


ARSENIC.  171 

it  volatilizes  at  about  450°  without  melting  and  forms  a  colorless  and 
odorless  vapor. 

The  molecular  weight  of  arsenic  vapors  at  450°  is  300.  As  the  atomic 
weight  of  arsenic  is  75,  it  follows  that  its  molecule  consists  of  4  atoms, 
analogous  to  that  of  phosphorus.  At  1700°,  on  the  contrary,  the  molecular 
weight  falls  to  150,  so  that  its  molecule  consists  of  only  2  atoms  at 
this  temperature  (dissociation,  p.  72). 

Arsenic  is  insoluble  in  hydrochloric  acid  and  dilute  sulphuric 
acid;  it  dissolves  in  dilute  nitric  acid  or  in  concentrated  sulphuric 
acid,  forming  arsenious  acid  (or  arsenic  trioxide,  process,  p.  174); 
in  concentrated  nitric  acid  or  in  aqua  regia  it  forms  arsenic  acid 
(p.  175).  On  heating  it  combines  directly  with  sulphur,  chlorine, 
bromine,  iodine,  and  most  of  the  metals,  and  when  finely  powdered  it 
burns  in  chlorine  gas  with  the  formation  of  arsenic  trichloride.  With 
the  exception  of  the  sulphur  and  haloid  compounds,  no  arsenic  salts 
are  known  (see  Antimony).  The  compounds  of  arsenic  with  the  metals 
(the  arsenides)  are  isomorphous  with  the  metaUic  sulphides  and  have 
an  analogous  constitution;  in  these  sulphur  and  arsenic  can  replace 
each  other  in  atomic  proportions. 

Arsenic  does  not  change  in  dry  air,  but  in  the  presence  of  water 
it  gradually  oxidizes  into  arsenic  trioxide  which  is  soluble  in  water. 
On  heating  in  the  air  it  burns  into  arsenic  trioxide  with  a  garlic- 
like  odor. 

Brown  arsenic  (corresponding  to  red  phosphorus)  is  produced  on 
heating  arseniureted  hydrogen  (p.  172)  or  ordinary  arsenic  in  a  current 
of  hydrogen.  It  forms  brownish-black,  metallic-like  masses,  and  in 
thin  layers  it  is  reddish  brown  and  transparent  and  consists  of  microscopic 
rhombohedra.  It  is  odorless  and  tasteless,  oxidizable  with  difficulty, 
insoluble  in  all  solvents,  has  a  specific  gravity  of  4.7,  and  vaporizes  above 
280°  without  melting,  and  m  then  transformed  into  the  white  modifica- 
tion. 

Yellow  arsenic  (corresponding  to  yellow  phosphorus)  is  produced 
by  subliming  ordinary  arsenic  in  carbon  dioxide  ;  it  condenses  on  the 
cold  part  of  the  apparatus  as  sulphur-like,  crystalline  masses,  readily 
oxidizable,  having  a  specific  gravity  of  3.9  and  an  odor  similar  to  garlic. 
It  dissolves  readily  in  carbon  disulphide  and  separates  from  this  solution 
on  evaporation  in  regular  rhombodecahedra.  At  ordinary  temperatures, 
even  in  the  dark,  it  is  quickly  transformed  into  ordinary  arsenic. 


172  INORGANIC  CHEMISTRY, 

a.  Compounds  with  Hydrogen. 

Gaseous  arseniureted  hydrogen,  AsHg. 
Solid  arseniureted  hydrogen,  As^Hj. 
Liquid  arseniureted  hydrogen,  AsgH^, 

is  not  known  free,  but  derivatives  of  the  same,  containing  hydrocarbon 
groups  such  as  cacodyl,  AsjCCHg)^  (see  Part  III),  are  known. 

Gaseous  Arseniureted  Hydrogen,  Arsenic HydrideorArsine,  AsHj. 

Preparation.  1.  It  is  obtained  pure  by  the  action  of  dilute 
sulphuric  acid  or  hydrochloric  acid  upon  an  alloy  of  arsenic  and  zinc: 
As2Zn3+  6HC1  =  2ASH3+  3ZnCl2. 

2.  Mixed  with  hydrogen  it  may  be  obtained  by  the  action  of 
nascent  hydrogen  upon  dissolved  arsenic  compounds.  If  a  solution 
containing  arsenic,  but  free  from  nitric  acid  (p.  173),  is  introduced 
into  a  flask  in  which  zinc  and  dilute  sulphuric  acid  are  present,  we 
obtain  the  gas  which  may  be  dried  by  passing  over  soHd  calcium 
chloride  (Marsh  apparatus). 

Properties.  Colorless,  very  poisonous  gas,  having  a  garlic-like 
odor,  liquefiable  at  —56°  and  solid  at  —114°  and  which  does  not 
combine  with  acids,  but  itself  shows  acid-like  characters  (p.  173). 
When  ignited  it  burns  into  arsenic  trioxide  and  water:  2AsH3+60=« 
AS2034-3H20;  if  a  cold  object,  for  instance  a  porcelain  dish,  is  held 
in  the  flame,  this  is  then  cooled  down  below  the  combustion  (oxida- 
tion) temperature  of  the  arsenic,  which  does  not  burn  into  its  oxide, 
but  deposits  as  brownish-black,  shining  spots,  so-called  "arsenic- 
stains,"  upon  the  porcelain. 

Arseniureted  hydrogen  is  decomposed  into  arsenic  and  hydrogen 
by  the  electric  spark  or  by  a  faint  white  heat;  hence  if  the  gas  is 
passed  through  a  heated  glass  tube,  the  arsenic  deposits  as  a  black, 
shining  coating,  so-called  "arsenic  mirror,"  after  having  passed  the 
heated  portion  of  the  tube. 

Arsenic  stains  and  arsenic  mirrors  consist  of  brown  arsenic  (p.  171)  ; 
they  volatiHze  on  heating  without  melting;  they  readily  dissolve  in 
sodium  hypochlorite  solution;  when  touched  with  nitric  acid  they 
dissolve,  forming  arsenic  acid  or  arsenious  acid;  if  this  solution  is 
neutralized  with  ammonia  and  treated  with  silver  nitrate  solution, 
brownish-red  silver  arsenate  or  yellow  silver  arsenite  are  produced 
(differing  from  antimony-stains,  p.  179). 


ARSENIC,  173 

Arseniureted  hydrogen  has  reducing  properties  and  precipitates 
various  metals  from  their  solution,  and  arsenious  acid,  which  is  pro- 
duced, remains  in  solution: 

ASH3+  6AgN03+  3H2O  =  6Ag+  H3ASO3+  6HNO3. 

Many  metals  are  precipitated  as  arsenides  by  AsHj: 

2ASH3+  3HgCl,  =  Hg3As2+  6HC1. 

If  AsHg  is  passed  over  paper  moistened  with  dilute  silver  nitrate  or 
mercuric  chloride  solution,  these  become  dark,  due  to  the  setting  free 
of  metallic  silver  or  the  formation  of  mercury  arsenide  (light  and  the 
presence  of  other  reducing  gases  being  excluded).  If  a  very  concentrated 
solution  of  silver  nitrate  is  used,  then  a  yellow  compound  of  AsAgg-H 
SAgNOg  is  produced  which,  when  moistened  with  water,  turns  black. 

Solid  arseniureted  hydrogen,  As^Hg,  is  obtained  as  a  reddish-brown 
powder  when  nascent  hydrogen  acts  upon  arsenic  compounds  in  the 
presence  of  nitric  acid.  (Hence  nitric  acid  must  be  absent  in  the  Marsh 
test  for  arsenic.) 

h.  Compounds  with  the  Halogens. 

These  are  obtained  by  the  direct  union  of  the  respective  elements 
and  have  similar  properties  to  the  corresponding  phosphorus  compounds. 
They  are  decomposed  by  water. 

Arsenic  trichloride,  AsCL,  is  also  produced  by  warming  AsgOg  or 
AS2O5  (which  see)  with  hydrochloric  acid.  It  forms  a  colorless,  thick 
liquid,  boiling  at  130°. 

Arsenic  penta-iodide,  Asl^,  the  only  arsenic  penta  compoimd  of  the 
halogens  known  in  the  free  state.     It  forms  red  crystals. 

Arsenic  tribromide,    AsBg,  forms  colorless  crystals. 

Arsenic  triiodide,    Aslg,  forms  reddish-yellow  crystals. 

c.  Compounds  with  Oxygen. 

A        .    x-«     -J         K    r\  \  (Arsenious  acid,       HoAsO,.) 

Arsemc  trioxide,      As,0,  ]  ^Metarsenious  acid,  HAsO;) 

fOrthoarsenic  acid,    H^AsC)^. 
Metarsenic  acid,       HAsOL 
Pyroarsenic  acid,     H^ASjOy. 
Arsenic  tetroxide,    ASgO^. 

Arsenic  Trioxide,  AsjOg  (white  arsenic?),  arsenious  anhydride,  or 
the  arsenious  acid  of  the  druggist. 

Occurrence.    In  the  mineral  kingdom  as  arsenolite. 

Preparation.  1.  By  burning  arsenical  ores  (as  a  by-product  in  the 
roasting  of  ores)  or  by  burning  arsenic  in  the  air.  The  arsenic  tri- 
oxide produced  vaporizes  and  is  passed  through  chambers  where  it 


174  INORGANIC  CHEMISTRY, 

condenses  as  a  white  crystalline  (octahedra)  powder  (white  arsenic  or 
arsenic  meal).  It  is  purified  by  sublimation,  and  is  obtained  as  a 
transparent  amorphous  colorless  mass  (vitreous  arsenic). 

2.  On  boihng  arsenic  with  sulphuric  acid  or  dilute  nitric  acid 
a  solution  of  arsenious  acid  is  obtained  which  on  evaporation  yields 
octahedral  crystals  of  arsenic  trioxide:  As+HN03+H20  =  H3As03+ 
NO;    2As+3H2S04  =  2H3As03+3S02;    2H3As03=As203+3H20. 

Properties.  It  volatilizes  at  220°  without  melting,  forming  colorless 
vapors  which  at  700°  have  a  density  corresponding  to  the  formula 
As^Oe,  and  at  1800°  to  the  formula  AsjO,  (dissociation,  p.  71).  On 
quickly  coohng  these  vapors  regular  octahedra  having  a  specific  gravity 
of  3.69  are  obtained,  while  on  slowly  cooling  monoclinic  prisms  having 
a  specific  gravity  of  4.0  are  obtained;  hence  it  is  dimorphous.  If 
AsjOg  is  heated  under  pressure  or  for  a  long  time  in  the  neighborhood 
of  220°,  it  becomes  amorphous  and  fusible  (formation  of  amorphous 
AsjOg  in  its  purification)  and  has  a  specific  gravity  of  3.74;  this  gradu- 
ally becomes  opaque,  white,  porcelain-Hke,  being  transformed  into 
octahedral  AsjOg.  Both  modifications  dissolve  in  hot  hydrochloric 
acid  without  forming  compounds,  and  separate  on  coohng  in  color- 
less, regular  octahedra. 

If  its  solution  in  hot  concentrated  hydrochloric  acid  is  boiled, 
then  AsClj,  which  volatihzes,  is  produced.  On  heating  AsPa  with 
carbon  (p.  170),  or  many  metals,  or  nascent  hydrogen,  it  is  reduced  to 
arsenic;  on  the  other  hand,  it  has  a  reducing  action  itself  (see  below) 
because  of  its  aptitude  to  be  converted  into  AsjOj.  It  dissolves  in 
water  with  difficulty,  the  amorphous  variety  somewhat  more  easily 
and  in  larger  quantities  than  the  crystaUine  form.  The  solutions 
have  a  faint  acid  reaction  and  may  be  considered  as  dissolved 

Arsenious  Acid,  H3As03(A,03+3H30=2H3As03).    This  acid  is 

not  known  free. 

Arsenites  are,  with  the  exception  of  the  alkali  salts,  insoluble  m 
water;  hence  freshly  prepared  ferric  hydroxide,  re(0H)3,  is  used  as 
an  antidote  in  arsenical  poisoning,  as  the  insoluble  ferric  arsenite, 
FeAs03,is  formed,  and  at  the  same  time  the  acid  of  the  gastric  juice, 
which  would  partly  dissolve  the  iron  arsenide,  is  neutrahzed.  Solu- 
ble arsenites  are  strong  reducing  agents,  as  they  are  readily  converted 
into  arsenates;  with  silver  nitrate  they  ^ve  a  yellow  precipitate  of 
silver  arsenite;  Ag3As03;    with  cupric  salts  a  green  precipitate  of 


ARSENIC,  175 

cupric  arsenite,  CuaCAsO^)^;    both  these  compounds  are  soluble  in 
nitric  acid  and  ammonia. 

Metarsenious  acid,  HAsOg  (behaves  towards  arsenious  acid  like  meta- 
phosphoric  acid  to  phosphoric  acid,  H3As03=HAs02  +  H20),  is  not 
known  free,  but  its  salts  are  known. 

Arsenic  pentoxide,  arsenic  anhydride,  AsjOs,  is  obtained  by 
gently  heating  (see  Arsenic  Tetroxide)  arsenic  acids  (which  see)  as  a 
white  porous  mass,  which  on  boiling  with  concentrated  hydrochloric 
acid  forms  volatile  arsenic  trichloride  and  free  chlorine,  as  the  arsenic 
pentachloride  formed  decomposes  immediately: 

AS2O5+  lOHCl  =  2ASCI5+  5H2O; 
2Asa  =  2AsCl3+4Cl. 

It  dissolves  in  water  and  is  slowly  converted  into  orthoarsenic  acid: 
AsA+3H20=2H3As04. 

Arsenic  Tetroxide,  AsgO^.  Arsenic  pentoxide  melts  on  strongly  heat- 
ing with  the  evolution  of  oxygen  and  forms  a  viscous,  yellow  liquid,  AsgO^, 
which  on  cooling  forms  an  amorphous,  vitreous  mass  that  decomposes 
into  AS2O3  +  O  on  stronger  heating. 

Orthoarsenic  acid,  H3ASO4,  arsenic  acid,  is  prepared  by  warming 
arsenic  or  arsenic  trioxide  with  aqua  regia  or  with  concentrated 
nitric  acid :  3As+  5HNO3+  SH^O  =  3H3 ASO4+  5N0 ; 

AS2O3+  2HNO3+  2H2O  =  2H3ASO4+  N0+  NOj. 

On  evaporating  the  solution,  colorless  rhombic  crystals   having  the 
composition  2H3ASO4+H2O  separate  out. 

Arsenates  are  analogous  to  the  salts  of  orthophosphoric  acid  and 
are  also  isomorphous  therewith.  Silver  nitrate  precipitates  reddish- 
brown  silver  arsenate,  AggAsO^,  from  their  solution,  and  this  precipi- 
tate is  soluble  in  ammonia  and  nitric  acid.  Precipitates  analogous 
to  the  phosphates  are  also  obtained  on  warming  with  ammonium 
molybdate  or  with  magnesia  mixture. 

Pyroarsenic  acid,  H^As^O;,  is  obtained  as  crvstals  by  heating  arsenic 
acid  to  180°:    2H3As04=H4As207  +  H20. 

Metarsenic  acid,  HAsOg,  is  produced  as  a  crystalline  mass  by  heating 
ortho-  or  pyroarsenic   acids   to   200°. 

On  dissolving  both  of  these  acids  in  water  they  yield  orthoarsessci 


176  INORGANIC  CHEMISTRY, 

acid.  The  salts  of  both  of  these  acids  are  produced  from  the  correspond- 
ing arsenates  in  a  manner  analogous  to  the  corresponding  phosphates 
(pp.  169,  170). 

d.  Compounds  with  Sulphur, 

The  following  three  compounds  are  known,  which,  like  the  sulphides 
of  phosphorus,  are  obtained  by  fusing  together  the  corresponding  quan- 
tities of  arsenic  and  sulphur. 

Arsenic  disulphide,  AsjSj,  is  found  native  as  realgar  in  readily 
fusible  ruby-red  crystals. 

Arsenic  trisulphide,  arsenious  sulphide,  AS2S3,  occurs  native  as 
orpiment  in  yellow  crystalline  masses.  It  is  obtained  as  a  yellow 
amorphous  powder  by  passing  HjS  into  a  solution  of  arsenious  acid 
containing  hydrochloric  acid,  or  into  a  solution  of  arsenite  or  of 
arsenic  acid  (see  below):   As203+3H2S=As2S3+3H20. 

Neutral  solutions  of  arsenious  acid  are  only  colored  yellow  by  H2S, 
as  colloidal  arsenic  trisulphide  (p.  53)  is  produced.  This  formation, 
which  is  analogous  to  the  formation  of  metallic  sulphides,  shows  the 
metallic  character  of  arsenic. 

AS2S3  is  insoluble  in  water  and  acids,  but  soluble  in  ammonia, 
caustic  and  fixed  alkalies. 

Arsenic  pentasulphide,  arsenic  sulphide,  AgSg,  is  prepared  by  passing 
HgS  into  potassium  arsenate  solution,  when  dissolved  potassium  sulpho- 
arsenate,  KgAsS^  (see  below),  is  produced,  from  which  hydrochloric  acid 
precipitates  arsenic  pentasulphide  as  a  pale-yellow  powder:  K3ASO4  + 
4H2S=K3AsS,  +  4H20;  2K3AsS,  +  6HCl=6KCl  +  3H2S  +  As2S5.  IfH^S  is 
passed  into  a  solution  containing  free  arsenic  acid  and  acidified  with  acid, 
sulphur  first  precipitates  out,  and  after  some  time  arsenic  trisulphide 
precipitates  because  the  H2S  first  reduces  the  arsenic  acid  into  arsenious 
acid:    AsA  +  2H,S=  AS2O3  +  2H2O  +  2S;  AsA  +  3H2S=  AS2S3  +  3H2O. 

If  HgS  is  rapidly  passed  into  a  warmed,  faintly  hydrochloric  acid 
solution  of  arsenic  acid  AsjSg  is  nevertheless  precipitated. 

Sulphoacids  and  sulphosalts  of  arsenic.  Just  as  we  have  sulphides 
which  are  analogous  to  the  oxides,  so  we  also  have  sulphur  arsenic 
salts  which  correspond  to  the  oxygen  arsenic  salts.  These  salts  are 
derived  from  the  following  unknown  acids: 

Sulphoarsenious  acid,  HgAsSg. 
Sulphoarsenic  acid,      H3ASS4. 

The  salts  of  these  acids  are  obtained  by  dissolving  the  correspond- 


ANTIMONY,  177 

ing   sulphide   in   potassium   or   ammonium   sulphide   solution    and 
evaporating,  etc.,  thus: 

AsjSj+SKjS  =2K3AsS3,  Potassium  sulphoarsenite. 
AsjSj+SKjS  =2K3AsS4,  Potassium  sulphoarsenate. 
As2S5+3(NH4)2S=2(NH4)2AsS4,  Ammonium  sulphoarsenate. 

Antimony,  tin,  gold,  platinum  form  similar  sulphosalts  (p.  181). 

e.  Detection  of  Arsenic  Compounds. 

1.  The  garhc-hke  odor  of  burning  arsenic,  which  is  produced 
when  all  its  compounds  are  heated  with  soda  upon  charcoal,  is  char- 
acteristic. 

2.  Sulphuretted  hydrogen  immediately  precipitates  yellow  arsenic 
trisulphide  from  acidified  solutions  of  arsenious  acid  or  arsenites, 
and  from  solutions  of  arsenic  acid  or  arsenates  only  after  passing 
the  gas  for  a  longer  time.  This  precipitate  is  soluble  in  alkali  and 
ammonium  sulphides  (see  above),  and  differs  from  all  other  yellow 
sulphides  (SbjSg,  SnSj,  CdS)  by  its  insolubility  in  hot  hydrochloric 
acid  and  its  solubihty  in  ammonia. 

3.  All  arsenic  compounds  when  heated  in  a  glass  tube  with  sodium 
carbonate  and  potassium  cyanide  yield  arsenic,  which  condenses  in 
the  upper  cold  portion  of  the  tube  as  an  arsenical  mirror  (p.  172). 

4.  Even  traces  of  arsenic  and  arsenic  compounds  (with  the  excep- 
tion of  arsenic  sulphide)  may  be  detected  by  converting  them  into 
ASH3  and  decomposing  this  by  heat  (Marsh  test  for  arsenic,  p.  172). 

5.  Stannous  chloride  dissolved  in  concentrated  hydrochloric 
acid  causes  a  precipitate  of  arsenic  from  the  HCl  solution  of  many 
arsenical  compounds,  even  when  they  contain  only  traces  of  arsenic 
(nitric  acid  being  absent).  This  takes  place  gradually  in  the  cold, 
and  is  shown  by  the  brown  coloration  in  the  previously  colorless 
solution  (Bettendorf's  arsenic  test) :  3SnCl2+ 6HCH- AS2O3  =  3SnCl4+ 
3H,0+2As. 

4.  Antimony  (Stibium). 

Atomic  weight  120.2=  Sb. 
Occurrence.     Seldom  free,  generally  as  antimony  glance  or  stib- 
nite,    SbiSa,    as    senarmontite,    Sb^Og,   and    as    kermesite,    Sb20S2. 
Also  in  many  nickel,  copper,  lead,  and  silver  ores,  combined  with 
sulphur  (p.  181). 


178  INORGANIC  CHEMISTRY. 

Preparation.  From  stibnite  by  heating  with  iron:  Sb2S3+3Fe  = 
3ireS+2Sb,  or  by  roasting  with  air,  when  sulphur  dioxide  is  devel- 
oped and  antimony  trioxide  remains:  Sb2S3+90  =  Sb203+3S02; 
the  antimony  oxide  is  then  reduced  to  metal  by  heating  with  carbon: 
Sb203+3C  =  2Sb+3CO. 

Properties.  Bluish-white,  metallic-like,  shining,  very  brittle 
masses  having  a  specific  gravity  of  6.7,  melting  at  630°,  and  on  solidi- 
fying forming  rhombohedral  crystals  similar  to  arsenic.  On  heating 
above  1450°  it  vaporizes,  and  does  not  change  in  the  air  at  ordinary 
temperatures,  but  burns  on  heating  in  the  air  into  white  odorless 
antimony  trioxide,  Sb203.  Like  phosphorus  and  arsenic,  it  com- 
bines directly  on  warming  with  the  halogens,  and  when  powdered 
it  inflames  in  chlorine  gas.  It  is  nearly  insoluble  in  hydrochloric 
acid  and  dilute  sulphuric  acid;  in  hot  concentrated  sulphuric  acid 
it  dissolves  with  the  formation  of  antimony  sulphate:  2Sb+  OHjSO^  = 
Sb2(S04)3+3S02+6H20;  nitric  acid  oxidizes  it  into  antimony  tri- 
oxide or  orthoantimonic  acid,  according  to  the  concentration.  Both 
of  these  bodies  are  insoluble  in  nitric  acid.  Aqua  regia  dissolves 
antimony,  forming  antimony  trichloride  or  antimony  pentachloride 
dependent  upon  the  length  of  action.  The  molecule  of  antimony 
consists  of  2  atoms  (p.  171). 

A  silver-white  modification  of  antimony,  having  a  specific  gravity  of 
5.8,  is  obtained  on  the  electrolysis  of  a  concentrated  solution  of  antimony 
trichloride  in  HCl. 

The  alloys  are  type-metal  (one  part  antimony,  four  parts  lead) 
and  Britannia  metal  (one  part  antimony  and  four  parts  tin). 

a.  Compounds  with  Hydrogen. 

Antimoniureted  hydrogen,  antimony  hydride  or  stibine,  SbH3, 
the  only  compound  of  antimony  with  hydrogen  (p.  172),  is  obtained  in 
the  same  manner  as  the  analogous  arsenic  compound. 

Properties.  It  is  a  colorless  gas  without  basic  properties,  has  a 
characteristic  odor,  and  becomes  liquid  at  low  temperatures  and  then 
solid.  It  burns  when  ignited  into  water  and  antimony  trioxide,  and 
is  more  readily  decomposable  by  heat  than  AsHg,  and  deposits 
in  spots  or  as  a  mirror,  similar  to  arsenic.  The  antimony  mirror  is 
produced  in  front  as  well  as  behind  the  portion  heated,  is  grayish 
black  and  less  volatile  than  the  arsenic  mirror,  and  melts  before  it 


ANTIMONY.  179 

volatilizes.  Antimony-stains  are,  contrary  to  the  arsenic-stains, 
dull  and  nearly  black,  insoluble  in  sodium  hypochlorite  solution, 
and  give  after  oxidation  with  nitric  acid  and  neutralization  with 
ammonia  a  black  stain  of  antimony  silver,  SbAgj,  with  silver  nitrate 
solution.  On  passing  SbH,  into  silver  nitrate  solution  all  the  anti- 
mony precipitates  as  SbAgj. 

h.  Compounds  with  the  Halogens 

are  prepared  like  the  corresponding  phosphorus  compounds.  They 
form  with  many  metallic  chlorides  readily  soluble,  crystalline  double  salts, 
which  are  used  as  mordants  in  dyeing:  thus,  NaCl  +  SbClg. 

Antimony  Trichloride,  Antimonous  Chloride,  SbClg.  Preparation. 
By  dissolving  antimony  oxide  or  antimony  sulphide  in  hydrochloric 
acid:  Sb2S3+6HCl  =  2SbCl3+3H2S.  This  is  then  distilled,  when 
first  HjS,  then  the  excess  of  hydrochloric  acid,  and  finally  the  antimony 
trichloride  pass  over. 

Properties.  Colorless,  fuming,  crystalline,  caustic,  soft  masses 
(hence  formerly  called  butter  of  antimony),  which  melt  at  73° 
and  boil  at  223°  and  which  absorb  water  from  the  air  and  deliquesce. 
Antimony  chloride  is  soluble  in  hydrochloric  acid;  if  this  solution 
or  solid  antimony  chloride  is  treated  with  considerable  water,  a 
white  crystalline  precipitate  of 

Antimony  oyxchloride,  SbOCl,  is  obtained.  This  was  formerly 
called  Algarot  powder.  It  contains  various  amounts  of  antimony 
trioxide  according  to  the  method  of  preparation: 

2Sba3+  3H2O  =  Sb^Oj  +  6Ha; 

Sba3+  H20=sboci+2Ha. 

Antimony  pentachloride,  antimonic  chloride,  SbClj,  is  a  yellowish 
fuming  liquid  which  crystallizes  at  —  6°  and  which  with  a  little  water 
sohdifies  into  crystals  having  the  composition  SbClj+HjO  or  SbCl5+ 
4H2O,  and  with  more  water  deposits  ortho-  or  pyroantimonic  acids 
(p.  180). 

c.  Compounds  with  Oxygen. 

Antimony  trioxide,     Sb.O,  { ^JSrorufacid,  gsl-'o^!" 

(Orthoantimonic  acid,  HgSbO^. 
Metantimonic  acid,      HSbOa- 
Pyroantimonic  acid,    H^SbjO;. 
Antimony  tetroxide,    SbjO^. 


180  INORGANIC  CHEMISTRY. 

Antimony  trioxide,  SbgOg  (according  to  vapor  density  Sb^Oj), 
antimonous  anhydride,  occurs  as  valentinite  in  rhombic  prisms, 
as  senarmontite  in  regular  octahedra  (isomorphous  with  both  forms 
of  arsenic  trioxide).  It  is  formed  on  the  burning  of  antimony  or  on 
treating  the  same  with  dilute  nitric  acid,  also  by  the  careful  heating 
of  antimonous  and  metantimonous  acids.  It  forms  a  white  crys- 
taUine  powder  which  fuses  and  sublimes  in  the  absence  of  air  (see 
Antimony  Tetroxide),  insoluble  in  water,  and  acts  like  metantimon- 
ous acid  towards  acids  and  alkalies. 

Antimonous  acid,  HgSbOg,  is  precipitated  as  a  white  precipitate  by 
treating  tartar  emetic  (see  below)  with  dilute  sulphuric  acid. 

Metantimonous  acid,  HSbOj,  is  obtained  from  HgSbOg  as  a  white  pow- 
der by  the  removal  of  water,  or  by  treating  antimony  trichloride  solution 
with  alkali  hydroxide  or  alkali  carbonate:  2SbCl3  +  3Na2C03  +  H20= 
2HSb02  +  6NaCl  +  3C02.  Both  acids  dissolve  in  an  excess  of  alkali  hy- 
drates, forming  metantimonites,  thus:  NaSb02;  the  solutions  decompose 
on  evaporation  with  the  setting  free  of  SbgOg.  They  act  like  bases 
towards  acids;  they  dissolve  in  hydrochloric  acid,  forming  antimony 
trichloride,  and  in  sulphuric  acid,  producing  antimony  sulphate,  Sb2(S04)3, 
and  are  insoluble  in  nitric  acid. 

The  monovalent  group  SbO,  called  antimonyl,  which •*is  contained  in 
the  metantimonous  acid,  SbO  (OH),  can  at  the  same  time  replace  the 
hydrogen  of  acids  with  the  formation  of  salts ;  for  instance,  in  antimonyl 
sulphate,  (SbO)2S04,  in  tartar  emetic,  C,H4K(SbO)Oe. 

Antimony  pentoxide,  antimonic  anhydride,  SbjOg,  is  obtained  by 
heating  the  antimonic  acids  to  400°.  It  forms  an  infusible,  amorphous, 
yellow  powder,  insoluble  in  water  and  nitric  acid,  but  soluble  in  hydro- 
chloric acid,  forming  SbCL,  and  soluble  in  alkalies,  forming  antimonales. 

Orthoantimonic  acid,  HgSbO^,  is  produced  on  warming  antimony  with 
concentrated  nitric  acid  or  on  mixing  antimony  pentachloride  with  cold 
water:  2SbCl5  +  8H2O=2H3SbO,  +  10HCl.  It  is  a  white  powder,  insolu- 
ble in  water,  ammonia,  nitric  acid,  but  soluble  in  hydrochloric  acid,  form- 
ing SbClg,  also  in  caustic  alkalies,  forming  antimonates  which  decompose 
even  on  evaporation. 

Pyroantimonic  acid,  H4Sb207,  is  produced  from  HgSbO^  on  heating  to 
200°,  as  well  as  by  mixing  SbClg  with  warm  water.  It  is  a  white  powder, 
soluble  in  large  quantities  of  pure  water,  in  caustic  alkalies,  ammonia, 
and  hydrochloric  acid:    2SbCl5  +  7H2O=H,Sb2O7+10HCl. 

The  most  important  salt  of  this  acid  is  the  secondary  sodium  pyroanti- 
monate,  NajHaSbgOy  +  eHgO,  as  it  is  the  only  sodium  salt  insoluble  in 
water. 

Metantimonic  acid,  HSbOg,  is  produced  from  ortho-  or  pyroantimonic 
acid  by  heating  to  300°,  and  forms  a  white  powder. 

Antimony  tetroxide,  Sb204,  also  considered  as  antimony  antimonate, 
(Sb^SbO^,  is  produced  when  any  oxygen  compound  of  antimony  is  heated 
in  the  air  (to  about  800°).  It' is  a  white  amorphous  powder  which  turns 
yellow  when  heated  and  which  does  not  melt  nor  volatilize.  It  is  insol- 
uble in  water,  but  soluble  in  caustic  alkalies  and  hydrochloric  acid. 


ANTIMONY.  181 

d.  Compounds  with  Sulphur. 

Antimony  trisulphide,  SbjSg,  occurs  in  gray,  brittle,  crystalline 
masses  as  stibnite.  It  is  a  constituent  of  many  minerals,  such  as 
tetrahedrite,  pyrargyrite,  bournonite,  etc.  (see  below).  It  is  readily 
fusible  and  volatile  at  higher  temperatures. 

It  may  be  obtained  as  an  amorphous  orange-red  powder  by  pass- 
ing sulphuretted  hydrogen  into  antimony  trichloride  solution :  2SbCl3+ 
3H2S=Sb2S3+6HCl.  It  is  soluble  in  alkaU  sulphides  (see  below) 
and  becomes  gray  and  crystalline  on  heating  in  the  absence  of  air. 

Antimony  oxy sulphide,  SbgOSg,  is  found  in  nature  as  kermesite,  and 
is  produced  on  melting  stibnite  with  an  insufficient  supply  of  air.  It 
forms  a  brownish-red  vitreous  mass  (antimony  vermilion).  A  mixture  of 
antimony  trisulphide  and  antimony  trioxide  is  called  kermes. 

Antimony  pentasulphide,  Sb2S5,  gold  sulphur,  is  obtained  by 
passing  sulphuretted  hydrogen  into  a  solution  of  antimony  penta- 
chloride:  2SbCl5+5H2S  =Sb2S5-f-10HCl,  or  by  decomposing  sodium 
sulphoantimonate,  Na3SbS4  (which  see),  with  acids.  It  is  an  orange- 
red  powder,  soluble  in  alkali  sulphides  (p.  182),  and  decomposes  on 
heating  into  SbaSg-l-Sj. 

Sulphoacids  and  Sulphosalts  of  Antimony.  Like  the  sulphides  of 
arsenic,  the  sulphides  of  antimony  form  compounds  with  metallic  sul- 
phides which  are  derivatives  of  the  following  acids  unknown  in  the  free 
state : 

Sulphantimonous  acid,  H3SbS3; 
Sulphantimonic  acid,      HgSbS^. 

The  salts  of  these  acids  are  obtained  in  a  manner  analogous  to  that  of 
arsenic  (p.  177) ;  these  salts  are  also  found  in  the  following  minerals; 

I  II   I 

Pyrargyrite,  AggSbSg,  Bournonite,  (PbCu)SbS3, 

II  II      II 

Tetrahedrite  group  or  Fahl  ores,  M3(SbS3)+MS=M4Sb2S7, 


where 


II      I  I      II    II     II  II 

M=Cu2,  in  part  Agg,  Fe,  Zn,  Hg;  thus,  (Cu2)3(Ag2)Sb2S7. 


e.  Detection  of  Antimony  Compounds. 

1.  By  the  obtainment  of  an  antimony  mirror  on  heating  the 
antimoniureted  hydrogen  gas  produced  (p.  178). 

2.  Soluble  antimony  salts  give  with  water  a  white  precipitate  of 
basic  antimony  salts,  which  are  soluble  in  tartaric  acid  (differing 
from  basic  bismuth  salts). 


182  INORGANIC  CHEMISTRY. 

3.  Solutions  of  antimony  compounds  acidified  with  hydrochloric 
acid  form  an  orange-red  precipitate  of  antimony  trisulphide  with 
sulphuretted  hydrogen.  This  precipitate  is  soluble  in  alkali  or 
ammonium  sulphide,  and  precipitable  from  this  solution  by  acids  as 
orange-red  antimony  pentasulphide. 

4.  If  the  substance  to  be  tested  is  placed  upon  a  piece  of  platinum- 
foil  with  a  small  piece  of  zinc  and  then  a  Httle  hydrochloric  acid  added, 
a  black  spot  of  metallic  antimony  will  be  obtained  upon  the  platinum. 
This  spot  cannot  be  washed  off  with  water. 

ARGON  GROUP. 

Argon.     Helium.     Neon.     Krypton.     Xenon. 

These  elements  seem  to  belong  to  the  nitrogen  group,  as  they  always 
accompany  the  free-occurring  nitrogen  and  replace  nitrogen  in  many 
minerals.  These  minerals  are  of  such  a  complicated  composition  that 
the  valence  of  argon,  etc.,  has  not  been  determined,  and  up  to  the  present 
time  no  compound  of  argon,  etc.,  has  been  obtained,  as  these  elements 
chemically  are  still  more  indifferent  than  nitrogen  (a  and  epyoi,  carrier). 
From  certain  physical  properties  it  follows  that  their  molecule  consists 
only  of  one  atom.  They  possess  characteristic  spectra  and  may  be  ob- 
tained on  the  fractional  distillation  of  liquid  air. 

I.  Argon. 

Atomic  weight  39.9=  A. 

Occurrence.  Free  in  the  air  (0.9  volumes  per  cent.)  and  to  a  less  extent 
in  the  gases  of  many  mineral  springs,  combined  to  a  somewhat  greater 
extent  in  rare  minerals,  such  as  clevite,  broggerite,  and  uranite,  nearly 
always  accompanied  with  helium. 

Preparation.  The  nitrogen  prepared  from  the  air  is  passed  over  heated 
magnesium  or  lithium,  which  combines  only  with  the  nitrogen.  The 
small  quantities  of  helium  which  are  nearly  always  present  cannot  at  the 
present  time  be  separated. 

Properties.  Colorless,  odorless,  and  tasteless  gas,  liquefiable  at  —185° 
and  crystalline  at  — 190°,  soluble  in  25  parts  water.  It  is  1.4  times  heavier 
than  air,  20  times  heavier  than  hydrogen;  1  liter  weighs  1.78  grams  (p. 
44).  The  characteristic  spectrum  consists  of  numerous  blue,  red,  and 
green  lines. 

2.  Helium. 

Atomic  weight  4= He. 

Occurrence.  It  occurs  free  as  traces  in  the  air  and  in  the  gases  of  cer- 
tain mineral  springs;  it  is  found  combined  to  a  greater  extent  in  certain 
rare  earths  which  contain  vanadium,  tantalum,  niobium,  thorium, 
yttrium,  uranium,  especially  in  cleveite,  euxenite  fergusonite,'  monazite] 


BORON.  183 

Hschynite,  and  to  an  enormous  extent  free  in  the  atmosphere  of  the  sun 
(hence  its  name)  and  of  the  fixed  stars. 

Preparation.  The  powdered  minerals  are  heated  in  order  to  remove 
water  and  gases,  which  are  less  firmly  combined  than  the  helium.      This 

Eroduct  is  then  heated  with  potassium  dichromate  in  a  vacuum,  when 
ehum  and  argon  are  evolved;  in  oider  to  separate  these  two  gases,  they 
are  exposed  in  a  Geissler  tube  with  magnesium  electrodes  to  a  strong 
electric  current,  when  the  argon  is  absorbed  by  the  magnesium. 

Properties.  Colorless,  odorless,  and  tasteless  gas,  liquefiable  at  —  250° 
and  nearly  insoluble  in  water.  Helium  is  0.14  times  lighter  than  the 
air  and  twice  as  heavy  as  hydrogen.  Its  characteristic  spectrum  consists 
of  bright  hnes  of  which  six  lie  in  the  red,  green,  blue,  and  violet;  the 
seventh,  which  is  especially  characterized,  occurring  in  the  yellow,  and 
indeed  to  the  right  of  the  yellow  sodium  lines. 


BORON. 

Atomic  weight  11  =  B. 

Boron  occurs  only  trivalent  and  belongs,  from  the  constitution 
of  its  compounds,  to  the  nitrogen  group,  and  from  its  position  in  the 
periodic  system,  as  well  as  the  behavior  of  certain  of  its  compounds, 
it  belongs  to  aluminum.  Most  of  the  boron  compounds  show  great 
similarity  to  the  corresponding  silicon  compounds.  When  free  it 
has  great  similarity  to  carbon  and  to  silicon. 

Occurrence.  Only  combined  as  boric  acid,  H3BO,  (which  see), 
and  in  the  tetraborates,  such  as  tinkal  or  borax,  Na2B407+  lOHjO,  in 
India.  Boracite,  4MgB407+2MgO+MgCl2  and  borocalcite,  CaB407+ 
6H2O,  occur  in  Stassfurt  salt.  Boron  is  also  found  to  a  trivial  extent 
in  many  plants. 

Preparation.  1.  By  heating  boron  trioxide  with  magnesium  when 
amorphous  boron  is  obtained:  B203  +  3Mg=3MgO  +  2B;  the  magnesium 
oxide  produced  is  dissolved  by  hydrochloric  acid. 

2.  Crystalline  boron  is  obtained  by  heating  amorphous  boron  or  boron 
trioxide  with  aluminium:  B,03  +  2A1=  A1A  +  2B.  The  boron  dissolves 
in  the  aluminium  and  crystallizes  out  on  cooling;  the  alummmm  is  dis- 
solved bv  hydrochloric  acid. 

Properties.  Amorphous  boron  is  a  brown  powder  having  a  specific 
gravity  of  2.45,  burns  on  heating  into  boron  trioxide,  combines  at  higher 
temperatures  with  chlorine,  bromine,  sulphur,  nitrogen,  also  with  plati- 
num and  silver  with  the  production  of  so-called  borides.  It  has  a  reduc- 
ing action,  hence  explodes  when  rubbed  with  lead  peroxides,  decolorizes 
potassium  permanganate  solution,  precipitates  metallic  silver  from  silver 
salt  solutions,  etc.  It  is  oxidized  into  boric  acid  by  boiling  with  nitric 
or  sulphuric  acid:  2B  +  3H2SO,=  2H3B03  +  3S02;  on  boiling  with  caustic 
potash  solutions  it  dissolves  with  the  formation  of  potassium  metaborate: 
2K0H  +  2B  +  2H2O  =  2KBO2  +  6H. 


184  INORGANIC  CHEMISTRY. 

Crystalline  boron  forms  colorless,  transparent  quadratic  crystals  hav- 
ing a  specific  gravity  of  2.63,  and  being  next  to  the  diamond  in  refrac- 
tive power  and  in  hardness.  It  is  not  oxidized  on  heating  and  is  not 
attacked  by  acids  and  caustic  potash  solutions.  When  fused  with  potas- 
sium hydroxide  both  modifications  yield  potassium  metaborate. 


Compounds  of  Boron. 

Gaseous  boron  hydride,  BH3,  is  produced  on  decomposing  a  fused 
mixture  of  boron  and  magnesium  with  hydrochloric  acid.  It  is  colorless, 
has  a  disagreeable  odor,  burns  with  a  green  flame  into  BgOg+SHgO;    it 

Erecipitates  black  silver  boride,  AggB,  from  silver  salt  solutions,  and  on 
eating  decomposes  into  its  constituents. 

Solid  boron  hydride  has  probably  the  formula  B4H2. 

Boron  trichloride,  BCI3,  and  also  boron  trifluoride,  BFg,  are  obtained 
in  the  same  way  as  the  similar  si  icon  compounds. 

Boron  nitride,  BN",  is  obtained  on  heating  amorphous  boron  in  nitrogen, 
as  a  white  amorphous  powder  which  is  insoluble  and  infusible.  If  steam 
is  passed  over  boron  nitride  at  200°,  boric  acid  and  ammonia  are  formed: 
BN  +  3H20=H3B03  +  NH3. 

Boron  carbide,  BeC,  produced  on  heating  boron  with  carbon  in  the 
electric  furnace,  forms  black  crystals  which  are  very  stable  and  next  to 
the  diamond  in  hardness. 

Boron  trioxide,  boric  anhydride,  B2O3,  is  obtained  by  heating  the 
boric  acids.  It  forms  colorless,  fusible,  vitreous  masses  which  are  only 
slightly  volatile  at  a  high  white  heat  and  which  dissolve  in  water,  form- 
ing boric  acid. 

Orthoboric  Acid,  H3BO3  or  B(0H)3,  Boracic  Acid.  Occurrence. 
Free  as  the  mineral  sassolite,  and  to  a  slight  extent  in  many  mineral 
waters  (Wiesbaden,  Aachen),  and  in  the  steam  which  is  evolved  in 
the  fumaroles  of  Tuscany  and  in  California,  and  streaming  from  the 
earth  in  the  Volcano  Islands.  Salts  of  this  are  not  found  in  nature 
(see  below). 

Preparation.  1.  In  Tuscany  the  vapors  from  the  "fumaroles" 
or  "  soffioni "  are  condensed  in  water  placed  in  basins.  These  solutions 
are  evaporated  in  flat  pans,  which  are  heated  by  the  vapors,  until  the 
boric  acid  crystallizes  out  and  which  is  then  purified  by  recrystal- 
Hzation. 

2.  In  Stassfurt  boracite  or  borocalcite  are  treated  with  hydro- 
chloric acid :    CaB,07+  2HC1+  5H,0  =  CaCl^^- 4H3BO3. 

3.  Chemically  pure  boric  acid  is  obtained  by  treating  a  hot, 
saturated  solution  of  borax  with  hydrochloric  acid  gas:  Na2B4074- 
2HCl+5H20  =  2NaCl+4H3B03;  the  boric  acid  which  separates  from 
the  solution  on  cooling  is  purified  by  recrystaUization. 


CARBON  GROUP.  185 

Properties.  Colorless,  shining  laminae  having  a  specific  gravity  of 
1.43,  possessing  a  fatty  touch,  and  which  are  soluble  in  3  parts  boil- 
ing and  25  parts  cold  water,  as  well  as  in  alcohol.  Boric  acid  is  a 
very  weak  acid,  but  on  account  of  the  slight  volatility  of  its  anhy- 
dride it  drives  out  most  acids  from  their  salts  on  heating  therewith. 

Detection.  The  lighted  alcoholic  solution  burns  with  a  green 
flame,  and  on  boiling  the  aqueous  solution  the  boric  acid  volatilizes 
with  the  steam.  Boric  acid  solutions  color  blue  litmus  paper  faint 
red,  turmeric  paper  reddish  brown  on  drying.  (Alkalies  turn  turmeric 
paper  brown  immediately,  and  acids  change  this  brown  into  yellow 
again.  Boric  acid  only  produces  a  brown  stain  after  drying,  which 
is  not  changed  by  acids  and  becomes  greenish  black  with  alkalies). 

Borates.  These  are  all  derived  from  tetraboric  acid;  only  organic 
salts  of  orthoboric  acid  are  known.  The  salts  of  metaboric  acid  are 
very  unstable.  All  borates  give  the  reactions  mentioned  for  boric 
acid  if  they  are  treated  with  hydrochloric  acid  for  the  turmeric  reac- 
tion and  with  sulphuric  acid  for  the  flame  reaction. 

Metaboric  acid,  HBO^,  is  obtained  by  heating  orthoboric  acid  to 
100°:    HgBOj^HBO^+H.O. 

Pyro=  or  Tetraboric  Acid,  H2B4O7,  is  produced  on  heating  ortho- 
or  metaboric  acids  to  140°:   4H3B03=H,B407+5H20; 

4HB02  =  H2B,07+  B,0. 

Perboric  acid,  HBO3,  is  known  only  in  the  form  of  salts,  which  are 
obtained  from  solutions  of  the  tetraborates  by  H2O2.  They  are  energetic 
oxidizing  agents. 

CARBON  GROUP. 

Carbon.     Silicon. 

Germanium.     Tin.     Lead. 

Titanium.     Zirconium.     Cerium.     Thorium. 

The  elements  of  the  first  two  series  are  di-  and  tetravalent;  lead  gen- 
erally occurs  divalent;  the  elements  of  the  last  series  are  tetravalent  only. 
Germanium,  tin,  lead,  bear  the  same  relationship  to  carbon  and  silicon 
that  arsenic,  antimony  and  bismuth  do  to  nitrogen  and  phosphorus.  As 
the  atomic  weight  increases,  the  character  of  the  elements  becomes  more 
metallic : 

+  17  +44  +45  +88 

N=14  P=31  As=75        Sb=120         Bi=208 

+  16  +44  +46  +89 

C=12         Si=28         Ge=72         Sn=118        Pb=207 

The  elements  of  the  second  and  third  series  show  even  more  metallic 
character  than  arsenic  and  antimony,   and  will  be  discussed  with  the 


186  INORGANIC  CHEMISTRY. 

metals.  They  do  not  combine  with  hydrogen,  but,  on  the  contrary, 
combine  with  the  halogens,  forming  volatile  compounds.  Their  mon- 
oxides are  bases,  while  their  dioxides  are  acid  anhydrides. 

I.  Carbon. 

Atomic  weight  12  =  C. 

Occurrence.  Free  in  three  allotropic  modifications  as  diamond, 
graphite,  and  amorphous  carbon,  which  in  their  properties  show  the 
greatest  differences  and  are  only  correspondent  with  each  other  through 
the  fact  that  they  all  yield  carbon  dioxide,  COj,  on  burning.  It  occurs 
combined  as  the  chief  constituent  of  all  animal  and  plant  substances 
and  the  products,  such  as  peat  and  various  coals,  produced  by  the 
slow  decomposition  of  plant  substances.  Combined  with  hydrogen  it 
forms  rock-oil  (petroleum)  and  asphalt;  as  carbon  dioxide  it  occurs 
combined  with  oxygen  in  the  air  and  in  the  carbonates,  such  as  marble, 
limestone,  chalk,  dolomite,  often  forming  entire  mountains. 

Preparation.     See  the  individual  modifications. 

Properties.  Solid,  odorless,  and  tasteless,  soluble  only  in  molten 
iron,  not  fusible,  only  volatile  at  about  3500°  in  the  electric  arc. 
At  ordinary  temperatures  it  remains  unchanged ;  at  higher  tempera- 
tures it  burns  into  carbon  dioxide  with  the  development  of  light 
and  heat  and  leaves  an  ash  which  consists  of  admixed  inorganic  sub- 
stances. At  a  white  heat  amorphous  carbon  abstracts  the  oxygen 
from  most  bodies  and  is,  therefore,  a  powerful  reducing  agent. 

Carbon  combines  with  fluorine  even  at  ordinary  temperatures; 
with  oxygen,  sulphur,  and  iron  at  a  red  heat;  and  with  hydrogen, 
boron,  silicon,  and  most  metals,  on  the  contrary,  at  about  3000°. 
Its  compounds  with  silicon,  boron,  and  the  metals  are  called  carbides 
and  are  characterized  by  their  stability  and  non-fusibility  at  the 
highest  temperatures  which  have  been  obtained  up  to  the  present 
time.  These  carbides  generally  form  beautiful  crystalline  masses  which 
are  decomposed  by  acids  and,  with  the  exception  of  iron  carbide, 
chromium  carbide,  and  titanium  carbide,  are  decomposed  by  water. 

Diamond  occurs  in  regular  rhombodecahedra,  seldom  as  octa- 
hedra,  generally  with  curved  surfaces  and  edges.  It  has  a  specific  gravity 
of  3.5,  is  transparent,  generally  colorless,  sometimes  red,  green,  blue, 
and  black,  readily  pulverizable,  is  a  non-conductor  of  electricity  and  a 
poor  conductor  of  heat.     The  diamond  possesses  the  greatest  brilliancy 


CARBON,  187 

and  of  all  bodies  has  the  highest  refractive  power,  as  well  as  the 
greatest  hardness,  as  it  can  only  be  pohshed  with  its  own  powder 
(bort).  When  heated  in  oxygen  it  burns  into  carbon  dioxide; 
when  strongly  heated  in  the  absence  of  oxygen  it  is  converted  into 
graphite;  even  the  strongest  oxidizing  agents  do  not  attack  it.  Dia- 
monds may  be  obtained  in  microscopic  crystals  by  dissolving  car- 
bon in  molten  iron  and  coohng  the  mixture  under  great  pressure. 

Graphite,  plumbago,  black  lead,  occurs  chiefly  as  amorphous,  scaly 
grayish-black  masses  which,  when  rubbed  on  paper,  leave  a  mark, 
and  is  used  in  the  lead-pencil  manufacture  and  as  iron  paint  (stove- 
polish).  It  seldom  occurs  in  the  crystalline  state  except  as  gray 
hexagonal  plates.  It  has  a  specific  gravity  of  2.25,  conducts  heat 
and  electricity  well,  is  more  difficult  of  combustion  in  an  oxygen 
current  than  the  diamond,  but  is  oxidized  by  strong  oxidizing  agents 
into  graphitic  acid,  C11H4O5,  or  meUitic  acid,  Q^^jR^fd^^' 

It  is  artificially  obtained  by  melting  amorphous  carbon  with  iron, 
when  the  carbon  dissolves  and  separates  out  in  black  plates  on 
cooling  the  iron. 

Amorphous  carbon  is  obtained  by  heating  many  organic  sub- 
stances (p.  4)  in  the  absence  of  air,  when  the  volatile  carbon  com- 
pounds are  driven  off  and  a  part  of  the  carbon  mixed  with  the  inorganic 
constituents  remains  behind.  It  forms  a  black,  voluminous  powder,  or 
gray  to  black  opaque  compact  masses  which  have  differing  specific 
gravities. 

a.  Lampblack  is  obtained  by  burning  substances  such  as  turpentine, 
rosin,  etc.,  which  are  very  rich  in  carbon  with  an  insufficient  supply  of 
air.  It  is  the  purest  form  of  amorphous  carbon  and  is  used  in  the  prepara- 
tion of  India  ink  and  printing-inks. 

h.  Wood  charcoal  is  obtained  by  the  carbonization  of  wood  in  heaps 
or  closed  vessels  (in  the  dry  distillation  of  wood).  It  shows  the  structure 
of  the  wood  and  is  porous,  hence  a  poor  conductor  of  heat  and  electricity. 
It  absorbs  gases,  pigments,  bitter  principles,  alkaloids,  and  many  metallic 
salts  from  their  solutions.  One  volume  of  wood  charcoal  absorbs  90 
volumes  of  ammonia  or  9  volumes  of  oxygen.  Because  of  this  property 
it  is  used  in  the  filtration  of  water,  in  the  absorption  of  putrefactive  gases, 
and  in  the  def  usilization  of  alcohol.  Freshly  heated  wood  charcoal  inflames 
in  the  air  spontaneously,  as  in  the  absorption  of  oxygen  heat  is  set  free. 

c.  Animal  charcoal,  bone-black,  ivory-black,  is  obtained  on  the  car- 
bonization of  animal  bodies  (blood-carbon,  bone-carbon).  It  absorbs 
gases,  coloring  matter,  etc.,  with  greater  activity  than  wood  charcoal,  as 
the  carbon  is  mixed  with  considerable  mineral  matter  and  hence  is  very 
finely  divided. 

d.  Gas-carbon,  retort  graphite,  deposits,  in  the  manufacture  of  illumi- 


188  INORGANIC  CHEMISTRY, 

nating  gas,  on  the  walls  of  the  retorts.  It  is  very  hard  and  dense,  a  good 
conductor  of  electricity,  and  is  used  in  galvanic  batteries. 

e.  Coke  remains  in  the  retorts  in  the  manufacture  of  illuminating-gas. 
It  conducts  heat  and  electricity. 

/.  Fossil  carbon  has  been  produced  from  prehistoric  plants  by  a 
form  of  decay  similar  to  carbonization,  where  the  hydrogen  and  oxygen  go 
off  in  great  part  as  water,  and  the  longer  the  process  goes  on  the  greater 
the  amount  of  carbon  is  left,  until  fuially  the  plant  structure  disappears 
completely.  Peat  contains  60  per  cent,  carbon,  brown  coal  70  per  cent., 
soft  coal  75-90  per  cent.,  and  anthracite  coal  95-98  per  cent,  carbon. 

a.  Compounds  with  Hydrogen. 

Carbon  and  hydrogen  unite  directly  and  indeed  at  high  tem- 
peratures, forming  only  acetylene,  CjHj,  methane,  CH4,  ethane,  CjHj; 
still  the  number  of  known  compounds  of  carbon  and  hydrogen  is 
very  great,  as  will  be  seen  later  in  Part  III. 

AH  compounds  of  carbon  may  be  derived  from  the  hydrocarbons,  as 
their  hydrogen  can  be  replaced  completely  or  in  part  by  other  atoms  or 
by  atomic  groups.  For  these  reasons  the  chemistry  of  the  hydrocarbons 
and  their  derivatives  is  treated  of  in  a  special  part,  and  the  old  term 
"organic  chemistry"  has  been  retained  for  this  part. 

h.  Compounds  with  the  Halogens 
are  obtained  indirectly  by  the  action  of  the  halogens  upon  the  hydro- 
carbons and  will  be  considered  in  this  connection. 

c.  Compounds  with  Oxygen. 
Carbon  monoxide,  CO. 
Carbon  dioxide,       COg.  Carbonic  acid,  HgCOg. 

Carbon  Monoxide,  CO.  Formation.  1.  In  the  combustion  of 
carbon  with  an  insufficient  supply  of  air,  as  in  furnaces  or  stoves 
with  closed  dampers,  or  by  burning  charcoal  in  braziers,  in  illuminat- 
ing-gas and  also  in  the  so-called  generator  gases. 

These  latter  are  produced  for  technical  purposes  in  specially  con- 
structed furnaces  (generators)  by  the  insufficient  combustion  of  deep 
layers  of  carbon  with  air,  and  consist  chiefly  of  carbon  monoxide  and 
nitrogen.  Dowson's  gas  is  a  mixture  of  generator-gas  and  water-gas 
(see  189). 

Preparation.  1.  By  passing  carbon  dioxide  over  heated  carbon 
when  the  volume  of  the  gas  is  doubled : 

1  mol.  =2  vol.  2  mol.  =4  vol. 

CO2  +C=  ^CO 


CARBON,  189 

By  passing  COj  over  red-hot  zinc-dust  or  by  heating  zinc-dust 
with  magnesium  or  calcium  carbonate,  when  the  latter  decomposes 
into  calcium  or  magnesium  oxide  and  carbon  dioxide  and  the  COj  is 
reduced  by  the  zinc  powder,  thus:   Zn-f-CaC03  =  ZnO+CaO+CO. 

2.  Ordinarily  by  heating  oxalic  acid  (C2H2O4)  with  sulphuric 
acid:  C2H204  =  H20-f  CO2+CO.  The  gaseous  mixture  obtained  is 
passed  through  a  watery  solution  of  potassium  hydroxide  which 
absorbs  all  the  CO2,  while  the  CO  passes  through  unchanged. 

Carbon  monoxide  may  also  be  obtained  by  warming  many  other  car- 
bon compounds,  such  as  citric  acid,  malic  acid,  formic  acid,  potassium 
ferrocyanide  (which  see)  with  sulphuric  acid.  Carbon  dioxide  is  also  pro- 
duced in  these  changes. 

3.  By  heating  an  excess  of  carbon  with  various  metallic  oxides, 
thus:  CuO-l-C  =  Cu+CO. 

4.  By  passing  steam  over  heated  carbon  a  mixture  of  carbon  monoxide 
and  hydrogen  (water-gas)  is  obtained:  C  +  H20=CO  +  2H.  This  mixture 
is  also  obtained  when  the  electric  arc  passes  between  carbon  poles  under 
water. 

Properties.  Colorless  and  odorless,  neutral  gas  0.967  times  lighter 
than  the  air  and  which  Hquefies  at  —190°.  It  is  nearly  insoluble  in 
water,  but  is  quickly  absorbed  by  a  solution  of  cuprous  chloride  in 
hydrochloric  acid  or  ammonia.  When  Ugh  ted  it  burns  in  the  air  with 
a  blue  flame  (characteristic)  into  carbon  dioxide;  it  does  not  support 
the  combustion  of  bodies,  but  on  account  of  its  tendency  to  form 
CO2  it  is  a  strong  reducing  agent,  especially  at  higher  temperatures. 
When  inspired  even  in  small  quantities  it  is  poisonous,  as  it  forms 
carbon  monoxide  haemoglobin  with  the  blood.  When  mixed  with 
oxygen  it  explodes  on  ignition;  it  combines  in  the  sunlight  with 
chlorine  and  bromine,  forming  COCI2  or  COBrg. 

It  combines  with  finely  divided  iron  and  nickel  at  38°  to  40°,  forming 
iron  or  nickel  carbonyl,  Fe(C0)4  or  Ni(C0)4,  both  colorless  refractive 
liquids,  and  with  potassium  (which  see)  it  forms  at  80°  solid  carbon  mon- 
oxide potassium  (C0K)6,  all  of  which  explode  on  heating.  Fe(C0)5  and 
Fe2(CO)7  are  also  known. 

When  exposed  with  H  to  the  dark  electric  discharge  it  forms  form- 
aldehyde: CO  +  H2=CH20;  and  with  water  it  forms  formic  acid: 
CO  +  H20=CH202.     With  fused  caustic  alkali  it  forms  alkali  formates. 

Detection.  1.  Because  of  its  reducing  powers  CO  darkens  paper 
moistened  with  palladium  chloride,  when  metallic  palladium  separates 
out :  PdCla  +  CO  +  H2O = Pd  +  2HC1  +  CO2.  In  order  to  test  for  CO  in  air 
it  is  passed  through  a  palladium  chloride  solution. 


190  INORGANIC  CHEMISTRY. 

^  2.  Carbon  monoxide  haemoglobin  possesses  a  characteristic  absorption 
spectrum  consisting  of  two  dark  bands  which  are  not  changed  by  reducing 
agents  (differing  from  oxyhsemoglobin  spectrum).  The  merest  traces  of 
carbon  monoxide  can  be  detected  by  passing  the  gas  to  be  tested  through 
dilute  blood,  and  investigating  this  with  a  spectroscope. 

3.  If  blood  containing  CO  is  treated  with  a  solution  of  potassium  ferro- 
cyanide  and  some  dilute  acetic  acid,  a  cherry-red  coagulum  is  produced, 
while  normal  blood  with  the  same  treatment  gives  a  dark-brown  coagulum. 

Carbon  oxychloride,  carbonyl  chloride,  phosgene  gas,  COClg,  is  ob- 
tained as  a  colorless  irritating  gas  by  mixing  equal  volumes  of  carbon 
monoxide  and  chlorine  in  the  sunlight  (hence  the  name).  This  gas  on 
cooling  condenses  to  a  colorless  liquid  which  boils  at  8°  and  is  characterized 
by  great  chemical  activity.  Water  decomposes  it  into  hydrochloric  acid 
and  carbon  dioxide:   COCl2  +  H20=C02  +  2HCl. 

Carbon  dioxide,  carbonic  anhydride  (erroneously  called  car- 
bonic acid),  CO2.  Occurrence.  It  is  produced  on  the  complete  oxida- 
tion of  all  carbon  compounds,  also  in  their  combustion,  in  respiration, 
in  decay,  and  is  hence  found  to  a  slight  extent  in  the  air  (p.  152) 
and  in  every  natural  water  (p.  116),  in  greater  quantities  in  the 
so-called  acid  waters.  It  streams  up  from  the  earth  in  large  quanti- 
ties in  volcanic  regions,  such  as  in  the  poisonous  valley  of  Java, 
in  the  dog-grotto  of  Naples,  in  Pyrmont,  and  in  the  crater  of  Eifel. 
It  is  often  found  in  deep  wells  and  mines  (choke-damp),  as  well  as 
absorbed  by  many  eruptive  rocks.  Carbon  dioxide  is  found  com- 
bined in  the  carbonates,  such  as  limestone,  CaCOj,  and  dolomite, 
CaCOg+MgCOg,  forming  entire  mountain  ranges.  It  occurs  enclosed 
in  certain  minerals  in  the  liquid  state. 

Formation.  1.  In  alcoholic  fermentation  (cause  of  accidents  in 
fermentation-vats) . 

2.  By  burning  carbon  with  an  excess  of  air  or  oxygen :  C+  20  =  CO2. 

3.  By  heating  carbon  witH  an  excess  of  metallic  oxides  (p.  189): 
2CuO+C  =  2Cu+C02. 

Preparation.  1.  Ordinarily  by  pouring  acids  upon  carbonates. 
Marble  and  hydrochloric  acid  are  generally  used:  CaC03-|-2HCl  = 
CaCl^+H^O+CO^. 

2.  By  heating  carbonates,  such  as  calcium  carbonate  (limestone) 
or  magnesium  carbonate:    CaC03  =  CaO-l-C02. 

Properties.  Colorless  and  odorless  gas  having  an  acid  taste, 
1.5  times  heavier  than  air,  and  as  a  product  of  complete  combustion 
is  not  combustible  nor  does  it  support  combustion.  The  presence 
of  a  few  per  cent,  of  carbon  dioxide  in  the  air  has  an  asphyxiating 


CARBON.  191 

action  since  the  elimination  of  carbon  dioxide  from  the  lungs  is 
very  much  slower  because  of  the  diminished  diffusion.  If  potassium 
or  magnesium  is  heated  in  CO2,  they  are  oxidized  and  the  carbon 
separates  as  amorphous  carbon.  At  —80°  or  at  0°  and  a  pressure 
of  39  atmospheres  (p.  41)  it  is  converted  into  a  colorless  neutral 
liquid  which  is  not  miscible  with  water  and  has  a  specific  gravity 
0.92  and  occurs  in  commerce  in  wrought-iron  cylinders. 

If  liquid  carbon  dioxide  is  allowed  to  flow  out  in  a  thin  stream, 
a  part  becomes  gaseous  immediately  and  takes  up  so  much  heat 
that  another  part  solidifies  into  snow-like  flakes  which  melt  at  —  65° 
under  a  pressure  of  3.5  atmospheres;  hence  solid  CO2  passes  immedi- 
ately into  the  gaseous  state  at  ordinary  temperatures  (p.  35). 

Solid  carbon  dioxide  volatilizes  only  slowly  on  lying  in  the  air,  when 
its  temperature  sinks  to  —  7S°.  A  mixture  of  the  same  with  ether  pro- 
duces, on  evaporation,  a  temperature  of  about  —90°;  if  this  mixture  is 
evaporated  under  the  air-pump  receiver,  its  temperature  falls  to  — 140°. 

One  volume  of  water  dissolves  at  15°  1  volume  carbon  dioxide. 
The  watery  solution  has  a  faint  acid  reaction,  the  dry  gas  itself  being 
neutral.  Carbon  dioxide  is  readily  absorbed  by  caustic  alkahes,  form- 
ing carbonates :    CO,-h  2K0H  =  K2CO3+  H,0. 

With  the  dark  electric  discharge  in  the  presence  of  water  or  hydro- 
gen CO2  is  converted  into  formic  acid:  002+211  =CH202;  CO2+ 
H20  =  CH202+0. 

Its  constitution  can  be  determined  by  burning  pure  carbon  in  a  known 
volume  of  oxygen,  when  on  cooling,  in  place  of  the  oxygen  used,  an  equal 
volume  of  carbon  dioxide  is  found.  Two  volumes  of  carbon  dioxide,  which 
weigh  44  parts,  contain  2  volumes  or  32  parts  by  weight  of  oxygen,  and 
hence  44  —  32=12  parts  by  weight  of  carbon. 

Carbonic  acid,  H2CO3  or  0=C  =  (0H)2,  is  not  known  free,  but  the 
aqueous  solution  of  carbon  dioxide  may  be  considered  as  a  solution 
of  carbonic  acid:  C02+H20=H2C03.  As  H2CO3  is  a  weak  aoid,  hence 
neutral  salts  formed  with  strong  bases  still  have  a  basic  reaction. 

Carbonates  may  be  obtained  by  saturating  bases  with  carbon 
dioxide:  2KOH+C02=K2C03+H20;  K2C03+H20+C02=2KHC03. 
They  are  decomposed,  with  effervescence,  by  every  stronger  acid, 
as  the  carbonic  acid  formed  immediately  decomposes:  K2CO3+ 
H2SO4  =  K2SO4+  H2CO3 ;  H2CO3  =  H2O+  CO2. 

Detection  of  Carbon  Dioxide  and  Carbonates.  If  a  glass  rod 
moistened  with  a  clear  solution   of  barium   or  calcium  hydrate  is 


192  INORGANIC  CHEMISTRY, 

introduced  into  a  vessel  containing  carbon  dioxide,  the  solution  be- 
comes cloudy  with  the  formation  of  insoluble  barium  or  calcium 
carbonate. 

The  carbon  dioxide  is  set  free  from  the  carbonates  by  the  addition 
of  an  acid  and  the  moistened  glass  rod  held  above  the  liquid.  Smaller 
quantities  are  detected  by  the  cloudiness  produced  in  the  above 
solutions,  when  the  gas  to  be  tested  is  passed  through  these  solu- 
tions for  a  longer  time. 

Percarbonic  acid,  UJO^O^  or  HO-COO-OOC-OH,  is  known  only  in  the 
form  of  salts,  the  percarbonates.  These  are  produced  when  an  aqueous 
solution  of  a  carbonate  is  exposed  to  electrolysis  below  — 10°.  In  aqueous 
solution  they  have  an  oxidizing  action  like  HgOg,  which  is  also  generated 
by  dilute  acids .  KAOe  +  2H2S04=  2KHSO4  +  H^O^  +  2CO2.  Water  or  bases 
at  ordinary  temperatures  develop  oxygen  from  these: 

H^Oe  +  2K0H  =  2KHCO3  +  H2O  +  O. 

d.  Compounds  with  Sulphur. 

Carbon  monosulphide,  CS. 

Carbon  disulphide,        CSg.  Sulphocarbonic  acid,  H2CS3. 

Carbon  monosulphide,  CS,  is  produced  as  dark  yellow  masses  when 
carbon  disulphide  and  hydrogen  or  carbon  disulphide  and  carbon  mon- 
oxide are  exposed  to  the  dark  electric  discharge: 

CS2  +  H2=CS  +  H2S;  CS2  +  C0=CS+C0S. 

Carbon  Disulphide,  CSj.  Preparation.  By  passing  sulphur 
vapors  over  heated  carbon  and  condensing  the  carbon  disulphide 
vapors. 

Properties.  Colorless,  highly  refracting  liquid,  having  a  specific 
gravity  of  1.27,  boiling  at  46°,  very  easily  inflamed,  and  burning  with 
a  bluish  flame :  CS2+  60  =  CO2+  2SO2.  When  pure  it  has  an  ethereal 
odor,  but  the  commercial  carbon  disulphide  has  a  very  unpleasant 
odor.  If  a  strong  current  of  air  is  blown  over  CSj,  it  rapidly  evapo- 
rates and  absorbs  so  much  heat  that  a  part  solidifies  into  a  white 
crystalline  mass.  When  the  vapor  is  inhaled  it  produces  poisonous 
symptoms;  when  mixed  with  oxygen  it  explodes  even  by  a  spark. 
It  readily  dissolves  sulphur,  phosphorus,  bromine,  iodine,  resins, 
rubber,  and  fatty  oils,  and  mixes  with  alcohol  and  ether  in  all  pro- 
portions, but  not  with  water. 

Sulphocarbonic  acid,  HjCSg,  is  prepared  from  the  sulphocarbonates  by 
acids  as  a  thick,  nauseating,  reddish-brown,  very  unstable  liquid. 


SILICON,  193 

Sulphocarbonates.  As  carbon  dioxide  unites  with  oxides,  forming  car- 
bonates, so  carbon  disulphide  combines  with  sulphides,  forming  sulpho- 
carbonates; thus  sodium  sulphocarbonate  is  produced  by  dissolving  carbon 
disulphide  in  sodium  sulphide  solution:    CSa  +  NaaS^NagCSy. 

Carbon  oxysulphide,  COS,  is  found  in  mineral  springs  and  is  produced 
by  passing  sulphur  vapors  and  carbon  monoxide  through  a  red-hot  tube, 
or,  better,  by  pouring  sulphuric  acid  upon  potassium  sulphocyanide 
(KCNS) ,  when  sulphocyanic  acid  is  set  free  which  takes  up  water,  forming 
carbon  oxysulphide  and  ammonia:  HCNS  +  H20=COS  +  NH3.  It  is  a 
colorless  gas  having  an  odor  similar  to  sulphuretted  hydrogen,  readily 
inflammable,  and  burns  into  carbon  dioxide  and  sulphur  dioxide. 

Monosulphocarbonic  acid,  HgCOgS  (=H20  +  C0S)  and 

Disulphocarbonic  acid,  HgCOSg  (=H2S  +  C0S)  are  known  only  as  salts. 

e.  Compounds  with  Nitrogen. 

One  compound  called  di cyanogen,  NC~CN,  is  known  which  forms 
numerous  other  compounds.  Dicyanogen  cannot  be  obtained  by 
direct  union  of  the  elements.  Dicyanogen  and  its  compounds  will  be 
treated  of  in  organic  chemistry. 

2.  Silicon,  or  Silicium. 

Atomic  weight  28.4=  Si. 

Occurrence.  Silicon  is,  next  to  oxygen,  the  most  widely  diffused 
of  the  elements,  but  does  not  occur  free.  Combined  with  oxygen, 
it  is  found  as  silicon  dioxide  or  silica  in  the  three  natural  kingdoms; 
silicates  form  many  minerals  and  nearly  all  crystalline  varieties  of 
rocks  (see  Silicon  Dioxide  and  Silicates). 

Preparation.  1.  By  heating  sodium  fluosilicate  with  metallic 
sodium:  Na2SiFe+4Na  =  6NaF+Si;  this  product  is  treated  with 
water,  which  dissolves  the  sodium  fluoride  and  leaves  the  amorphous 
silicon. 

2.  Alloyed  with  some  magnesium  it  may  be  obtained  by  fusing 
sand  (SiOg)  and  magnesium  powder  together. 

3.  If  zinc  be  added  in  this  method  of  preparation,  then  the 
silicon  dissolves  in  the  molten  zinc  and  separates  on  cooling  as  crys- 
taUine  silicon,  which  remains  on  dissolving  the  zinc  in  hydrochloric 
acid. 

Properties.  Crystalline  silicon  forms  black  octahedra  of  a  specific 
gravity  2.5,  which  scratch  glass;  it  is  not  oxidized  on  heating  in  the 
air,  and  melts  at  about  1500°. 

Amorphous  sihcon  is  a  reddish-brown  powder  with  the  specific 


194  INORGANIC  CHEMISTRY. 

gravity  2.35  and  burning  in  the  air,  forming  SiOj.  Both  modifications 
are  insoluble  in  acids;  on  heating  in  chlorine  gas  they  burn  into 
sihcon  chloride;  on  boiUng  with  caustic  potash  solution  they  dis- 
solve, forming  alkali  silicates:  Si+4KOH=K4Si04+4H. 

The  compounds  of  silicon  with  the  metals  are  called  silicides — for 
example,  barium  silicide,  BaSig — and  are  obtained  by  heating  the  respective 
metallic  oxide  wth  carbon  and  silicic  acid  to  about  3000°.  They  form 
white  crystalline  masses  which  are  decomposed  by  water. 

a.  Compounds  of  Silicon. 

Silicon  hydride,  SiH^,  is  prepared  in  a  similar  manner  to  arsenic  hydride 
by  dissolving  an  alloy  of  silicon  and  magnesium  in  dilute  hydrochloric 
acid,  SiMg2  +  4HCl=SiH4  +  2MgCl2,  as  a  colorless  gas.  Even  on  gently 
warming,  it  inflames  and  burns  into  water  and  silicon  dioxide,  the  latter 
forming  a  ring-like  cloud.  If  the  gas  is  diluted  with  hydrogen,  it  is  spon- 
taneously inflammable. 

Silicon  chloride,  SiCl^,  is  produced  on  heating  silicon  or  a  mixture  of 
sihcon  dioxide  and  carbon  in  chlorine  gas:  Si02  +  2C  +  4Cl=SiCl4  +  2CO. 
It  is  a  colorless,  fuming,  irritating  liquid  which  boils  at  75°  and  which 
decomposes  with  water,  forming  siHcic  acid :  SiCl^  +  4H2O  =  H^SiO^  +  4HC1. 

Silicon  chloroform,  SiHClg,  so  called  because  it  is  similarly  constituted 
to  chloroform,  CHCI3,  is  obtained  with  silicon  chloride  on  heating  sihcon 
in  hydrochloric  gas.  It  is  a  colorless,  fuming  Hquid  which  boils  at  36°, 
and  which  is  readily  inflammable. 

Besides  these  compounds,  other  silicon  compounds  having  an  analogous 
constitution  to  the  corresponding  carbon  compounds  are  known  (see 
compounds  of  the  alcohol  radicals  with  metalloids  in  Part  III). 

Silicon  carbide,  SiC,  which  is  next  to  the  diamond  and  boron  carbide  in 
hardness,  is  not  attacked  by  any  acid,  and  is  more  stable  with  heat  than 
the  diamond.  It  forms  colorless  needles  which  are  prepared  by  the 
reduction  of  sand  (SiOj)  with  carbon  in  the  electric  furnace.  It  is  used 
under  the  name  of  carborundum  as  a  substitute  for  emery  and  diamond- 
powder. 

Silicon  Fluoride,  SiF^.  Preparation.  By  the  action  of  hydro- 
fluoric acid  upon  sihcon  dioxide  or  a  silicate. 

Calcium  fluoride  and  sand  (SiO^)  or  glass  powder  is  warmed  with  sul- 
J3huric  acid.  First  hvdrofluoric  acid  is  formed,  which  then  acts  upon  the 
silicon  dioxide:  2CaF2  +  H,S04=CaSO,  +  4HF;  4HF+Si02=2H.O  +  SiF4. 
The  water  formed  unites  with  the  sulphuric  acid,  and  silicon  fluoride  is 
evolved. 

Properties.  Colorless,  irritating,  fuming  gas  which  is  neither 
combustible  nor  supports  combustion,  and  is  liquefiable  at  -160°. 
It  is  decomposed  by  water  into  silicic  acid  and  hydrofluosilicic 
acid:  3SiF4+4H20=2H2SiF6+H,Si04;  the  gelatinous  sihcic  acid 
is  removed  by  filtration,  and  the  watery  solution  of 


SILICON.  195 

Hydrofluosilicic  acid,  HjSiFg,  is  obtained.  This  is  an  acid,  fum- 
ing, colorless  liquid;  it  is  not  known  in  the  anhydrous  state;  on 
evaporation  in  a  platinum  vessel  it  leaves  no  residue,  as  it  decom- 
poses into  volatile  SiF^  and  2HF.  It  forms  salts,  the  silicofluorides, 
with  bases.  KaSiFg  and  BaSiFg  are  insoluble  in  water,  hence  they 
are  used  in  the  quantitative  estimation  of  potassium  and  barium. 

Silicon  sulphide,  SiSg,  is  obtained  by  heating  amorphous  silicon  with 
sulphur,  and  forms  silky  prisms  which  are  decomposed  by  water: 
SiSa  +  4H2O  =  H.SiO,  +  2H2S. 

Silicon  Dioxide,  Silica,  Sihcic  Anhydride,  SiOa-  Occurrence.  It 
forms  as  silicates  the  chief  constituent  of  the  earth's  crust  and  is  a 
constituent  of  all  plants  and  animals  (see  Sihcic  Acids).  It  occurs 
free  in  the  crystalline  as  well  as  in  the  amorphous  state. 

Crystalline  siUcon  dioxide  occurs  as  rock  crystals  in  transparent, 
colorless,  hexagonal  columns,  and  as  quartz  as  colorless,  opaque, 
granular  masses.  Both  of  these  occur  in  many  modifications,  espe- 
cially as 

Citrine,  gold  topaz,  when  transparent  and  pale  yellow. 

Amethyst  when  transparent  and  violet  by  manganese. 

Smoky  topaz  when  transparent  and  colored  brown  or  black  by  bitu- 
minous matter. 

Tridymite,  in  hexagonal  twin  crystals. 

Common  quartz  when  opaque,  gray,  or  yellowish. 

Milky  quartz  when  opaque,  milky  white. 

Rose-quartz  when  opaque,  rose-color. 

Agate,  aventurine,  chalcedony,  chrysoprase,  flint,  heliotrope,  jasper, 
camelian,  cat's-eye,  onyx,  tiger-eye,  are  mixtures  of  amorphous  and  crys- 
talline silicon  dioxide  having  various  colors  and  occurring  as  minerals. 

Quartz  is  the  chief  constituent  of  granite,  syenite,  and  gneiss.  In 
boulders  and  grains  (sand)  quartz  covers  a  great  part  of  the  earth's  sur- 
face; sandstone  consists  of  individual  quartz  granules  which  are  united 
together  by  some  other  substance. 

Amorphous  silicon  dioxide  is  found  as  opal  in  colorless  or  colored 
vitreous  masses,  and  also  in  many  vitrifications;  tripoHte  or  infusorial 
earth  consists  of  the  siliceous  shells  of  infusoria. 

Preparation.  Amorphous  sihcon  dioxide  is  obtained  by  burning 
amorphous  silicon  or  by  heating  silicic  acid.  It  forms  white,  soft 
powder.  Crystalhne  silicon  dioxide  is  obtained  by  heating  dialyzed 
sihcic  acid  (see  below)  under  pressure  for  a  long  time  or  by  strongly 
heating  amorphous  silicon  dioxide  for  a  long  time. 


196  INORGANIC  CHEMISTRY. 

Properties.  It  is  only  soluble  in  hydrofluoric  acid.  When  boiled 
with  alkali  hydroxide  solution  the  amorphous  SiOj  dissolves,  forming 
the  corresponding  sihcate  (p.  197).  The  amorphous  form  has  a  spe- 
cific gravity  of  2.2,  the  crystallized  a  specific  gravity  of  2.6.  It 
melts  in  the  oxyhydrogen  blowpipe-flame. 

Detection.     Similar  to  the  sihcates  (p.  197). 

Silicic  Acids.  Occurrence.  The  sihcates  form  the  chief  constitu- 
ent of  most  rocks  (see  Aluminium)  and  many  minerals  and  are  found  in 
the  animal  kingdom,  especially  in  the  sheU  of  infusoria,  in  feathers, 
hair,  and  quills.  They  occur  in  the  plant  kingdom,  especially  in  many 
grasses,  in  straw,  and  in  rattan.  Dissolved  silicic  acid  occurs  free  in 
many  mineral  waters,  especially  in  the  hot  springs  of  Iceland  and 
New  Zealand,  which  deposit  in  the  air  as  compact  masses  (sihceous 
sinter). 

1.  Orthosilicic  Acid,  H4Si04.  If  fine  sand  is  fused  with  sodium 
carbonate,  it  forms  a  vitreous  mass,  soluble  in  hot  water,  consisting 
of  sodium  silicate  (sodium  water-glass):  2Na2C03+Si02  =  Na4Si04+ 
2CO2.  If  hydrochloric  acid  is  added  to  this  solution,  orthosihcic 
acid  is  set  free :  Na4Si04+  4HC1  =  4NaCl+  H4Si04,  which  separates  in 
part  as  a  gelatinous  mass  containing  water,  while  another  part  remains 
in  solution,  as  it  is  somewhat  soluble  in  water,  but  more  soluble  in 
dilute  HCl. 

A  solution  of  pure  sihcic  acid  can  be  obtained  from  the  above 
solution,  containing  NaCl  and  HCl,  by  means  of  dialysis,  as  silicic 
acid  is  a  colloid,  while  the  impurities  are  crystalloid  and  diffuse  through 
the  membrane  of  the  dialyzer  (p.  47). 

The  sihcic  acid  solution  obtained  by  dialysis  is  colorless,  faintly 
acid,  and  may  be  concentrated  by  evaporation,  but  soon  sohdifies 
into  a  transparent  jelly  (sihcic  acid  gele,  p.  54)  of  sihcic  acid,  which  can 
be  precipitated  from  the  silicic  acid  solution  by  very  small  amounts 
of  sodium  carbonate  or  other  salts.  If  the  evaporation  is  continued 
to  dryness,  we  obtain  a  fine  white  amorphous  powder  having  the 
composition  HjSiOg+xSiOj. 

Orthosilicic  acid  has  not  been  obtained  pure  because  on  drying 
it  gives  off  water  and  is  then  mixed  with  metasilicic  acid  or  polysiHcic 
acids: 

H4Si04  =  H2Si03+H20; 
2H4Si04  =  HeSi07+H20. 


SILICON.     '  197 

2.  MetasUicic  acid,  H2Si03,  corresponding  approximately  to  the 
preceding  formula,  is  obtained  when  orthosilicic  acid  solution  is  evapo- 
rated under  the  air-pump  receiver  at  15°  and  the  glass-hke  residue 
dried  over  sulphuric  acid. 

3.  Polysilicic  Acids.  As  the  polybasic  sulphuric  acid,  phosphoric 
acid,  and  arsenic  acid  may,  by  condensation  of  several  molecules 
with  the  elimination  of  water,  form  anhydro-  or  poly-acids,  so  also 
does  sihcic  acid,  and  in  fact  to  a  much  greater  extent.  There  are  a 
great  number  of  polysilicic  acids  which  are  only  known  mixed  with 
each  other.  According  to  the  number  of  silicon  atoms  contained 
in  the  molecule,  we  call  the  respective  acids  di-,  tri-,  tetra-,  pentasilicic 
acid,  etc.,  and  the  corresponding  salts  di-,  tri-,  tetra-,  pentasiUcates, 
etc. 

H2SiA  =  H2Si03+Si02  or  =2H,Si04-3H20. 

HeSi207  =  H,Si04+H2Si03  "  =2H,Si04-  H^O. 

H2Si307=H2Si03+2SiQ2  "  =3H,Si04-5H20. 

H4Si308=2H2Si03+Si02  "  =  SH^SiO^  -  4H2O. 

On  heating,  all  sihcic  acids  yield  Si02. 

Silicates.  The  silicates  occurring  in  nature  are  nearly  all  derived 
from  the  polysilicic  acids  and  only  a  few  are  derived  from  ortho- 
or  metasilicic  acid.  Artificially  silicates  are  obtained  as  amor- 
phous, vitreous  masses  by  fusing  sihcic  anhydride  (p.  195)  with 
bases  or  metaUic  carbonates.  They  are  insoluble  in  water  (with  the 
exception  of  the  alkali  silicates)  and  are  decomposed  by  acids  with 
the  separation  of  silicic  acid. 

Of  the  natural  silicates,  only  a  few  are  decomposed  by  acids, 
most  of  them  not  being  attacked  at  all.  Such  silicates,  in  order 
to  be  able  to  determine  the  metals  contained  therein,  must  be  first 
made  decomposable  by  acids,  which  is  done  by  fusing  the  finely 
powdered  substance  with  dried  sodium  carbonate. 

Detection.  If  silicic  anhydride,  silicic  acid,  or  a  silicate  is  melted 
on  a  platinum  loop  with  phosphorus  salt  (which  see),  then  the 
bases  dissolve  in  the  metaphosphate  produced,  while  sihcic  acid 
separates  and  causes  the  otherwise  clear  bead  to  become  opaque, 
forming  the  so-called  silica  skeleton. 


II.  METALS. 

For  reasons  given  on  page  95  the  elements  which  are  called  metals 
are  divided  into  the  following  groups: 

1.  Potassium,  sodium,  caesium,  rubidium,  lithium  (ammonium). 

2.  Calcium,  barium,  strontium. 

3.  Beryllium,  magnesium,  zinc,  cadmium. 

4.  Copper,  silver,  mercury. 

5.  Aluminium,  gaUium,  indium,  thaUium,  scandiiun,  yttrium, 
lanthanum,  cerium,  praseodymium,  neodymium,  samarium,  gado- 
linium, erbium,  thulium,  ytterbium. 

6.  Tin,  zirconium,  titanium,  thorium. 

7.  Bismuth,  vanadium,  tantalum,  niobium. 

8.  Chromium,  molybdenum,  tungsten,  uranium. 

9.  Iron,  manganese,  cobalt,  nickel. 

10.  Gold,  platinum,  osmium,  iridium,  ruthenium,  rhodium, 
palladium. 

Properties.  The  metals  have  more  properties  in  common  than 
the  non-metals.  The  metals  are  non-transparent,  and  only  certain 
of  them  are  transparent  in  very  thin  layers.  With  the  exception  of 
mercury  they  are  all  solids  at  ordinary  temperatures. 

When  compact,  especially  when  the  surface  is  pohshed,  they 
have  a  pecuUar  shine,  which  has  been  called  metaUic  lustre.  When 
finely  divided  they  form  dark  powders.  They  are  good  conductors 
of  heat  and  electricity.  The  color  of  most  metals  is  white  to  bluish 
gray.  Copper  is  red;  gold,  barium,  and  strontium  are  yellow.  Most 
metals  are  crystalline  in  regular  systems.  Only  a  few,  having  a 
metalloid  character,  are  not  regular  in  their  crystallization;  thus  bis- 
muth crystallizes  in  the  hexagonal  system,  and  tin  in  the  quadratic 
system. 

The  specific  gravity  of  the  metals  is  very  different  and  variable, 
from  0.59,  the  specific  gravity  of  hthium,  to  22.5,  the  specific  gravity  of 
osmium.      Metals  whose  specific  gravity  is  below  5  are  called  light 

198 


METALS.  199 

metals,  and  those  above  are  called  heavy  metals.  Most  metals  are 
malleable  and  tough  and  may  be  converted  into  foil  and  wire.  Only 
bismuth  and  tin,  which  have  metalloid  character,  are  brittle. 

All  metals  are  fusible.  Mercury  has  the  lowest  melting-point, 
namely,  —40°;  potassium  melts  at  63°,  zinc  at  243°,  copper  at  1100°, 
platinum  at  1770°,  iridium  at  1950°,  chromium  at  2100°,  osmium 
at  2500°.  All  metals  can  be  converted  into  a  vaporous  state;  their 
volatility  corresponds  to  their  fusibility.  Mercury  vaporizes  at  360°, 
zinc  at  about  1000°;  platinum  and  the  other  difficultly  fusible  metals 
can  be  vaporized  in  the  electric  furnace. 

No  metal  in  the  compact  condition  is  soluble  as  such.  If  the  sol- 
tion  of  a  metal  in  acids  or  bases  is  evaporated,  we  obtain  a  salt  or 
oxide.  On  the  contrary,  numerous  metals  are  soluble  in  water  at 
the  moment  when  they  are  precipitated  from  the  solution  of  their  salts 
in  a  very  finely  divided  state  (see  Colloidal  Solution,  p.  53). 

The  metals  are  as  a  rule  more  active  chemically  than  the  metalloids, 
as  the  molecule  of  the  metals  consists  only  of  an  atom,  while  in  the 
metalloids  the  molecule  must  be  first  split  into  atoms.  The  metalloids 
are  therefore  more  active  in  the  nascent  state  than  in  the  ordinary 
condition,  where  the  atoms  have  already  united  to  form  molecules 
(p.  16). 

The  combinations  of  the  metals  between  themselves  according 
to  no  certain  proportion  by  weight  are  called  alloys  (p.  49).  These 
generally  have  the  average  properties  of  the  metals  of  which  they  are 
composed,  so  that  it  is  possible  to  obtain  alloys  by  the  selection  of 
suitable  metals  which  have  properties  of  technical  importance.  The 
alloys  with  mercury  are  called  amalgams. 

The  color  of  the  alloys  is  different  according  to  the  constituents;  still 
it  is  independent  of  the  proportion  of  the  metals;  thus  an  alloy  of  copper 
with  30  per  cent,  of  tin  is  white,  while  with  30  per  cent,  zinc  it  is  yellow. 
The  hardness  and  toughness  are  generally  greater  than  those  of  the  individ- 
ual metals,  while  the  melting-point  is  lower,  and  often  lower  than  that  of 
the  metal  having  the  lowest  melting-point;  thus  a  mixture  of  2  parts 
bismuth,  1  part  tin,  and  1  part  lead  (Wood's  metal)  melts  at  94°,  while 
pure  bismuth  melts  at  270°,  tin  at  235°,  and  lead  at  334°.  The  melting- 
point  of  amalgams  lies  always  above  that  of  mercury.  Acids  often  attack 
alloys  with  greater  difficulty  than  the  constituents  alone ;  still  many  alloys 
are  dissolved  by  acids  which  would  not  dissolve  the  metals  contained  in 
the  mixture. 

The  compounds  of  the  metals  with  the  non-metals  do  not  have 
the  properties  of  the  metals.     While  the  oxides  of  the  non-metals 


200  INORGANIC  CHEMISTRY. 

are  nearly  all  acid-forming,  only  a  few  of  the  higher  oxides  of  the 
metals  are  acid,  while  most  of  the  metallic  oxides  are  basic  in  character. 
The  compounds  with  hydrogen  are  colorless  powders  with  the  excep- 
tion of  palladium,  sodium,  and  potassium,  which  are  metallic  in 
appearance;  gaseous  combinations  of  hydrogen  with  the  metals  are 
not  known.  The  halogen  compounds  of  the  metals  are  mostly  very 
stable,  while  those  of  the  metalloids,  with  the  exception  of  those 
with  carbon,  are  readily  decomposed  by  water. 

The  combinations  with  boron,  silicon,  and  carbon  (borides,  sili- 
cides,  carbides)  are  not  volatile  even  at  the  temperature  of  the  electric 
furnace.  The  carbides  (p.  186)  have  great  technical  importance. 
We  differentiate  between  the  metals  according  to  their  chemical 
behavior  into — 

1.  Non-nohle  Metals.  Certain  of  these  oxidize  even  on  being 
exposed  to  the  air,  but  all  oxidize  on  being  heated.  They  decom- 
pose water  either  at  ordinary  temperatures  (alkali  metals,  alkaline 
earths)  or  at  higher  temperatures  (with  the  exception  of  lead,  bismuth, 
and  copper). 

2.  Noble  Metals.  These  show  slight  affinity  for  oxygen  and  do 
not  change  in  the  air.  They  do  not  decompose  water  even  at  high 
temperatures,  and  their  indirectly  obtained  oxides  decompose  on 
heating  into  the  metal  and  oxygen.  To  this  group  belong  silver, 
gold,  platinum,  also  mercury  and  certain  rare  platinum  metals  which 
indeed  oxidize  when  heated  in  the  air,  but  decompose  again  into 
metal  and  oxygen  when  heated  to  a  higher  degree. 

Occurrence.  1.  Mercury,  silver,  copper,  arsenic,  antimony,  bis- 
muth, lead,  rarely  iron  are  found  combined  as  well  as  free  (native). 
Gold  and  the  platinum  metals  occur  nearly  entirely  free,  as  they  only 
have  a  slight  affinity  for  oxygen  and  are  not  at  all  or  only  slightly 
changed  by  atmospheric  influences. 

2.  Most  of  the  heavy  metals  do  not  exist  in  a  free  state.  The 
naturally  occurring  compounds  of  the  heavy  metals  are  called 
ores. 

3.  The  fight  metals  to  which  the  elements  of  the  potassium,  cal- 
cium, and  aluminium  groups,  and  magnesium  and  certain  rare  metals 
belong  do  not  occur  native,  but  are  found  chiefly  as  silicates,  these 
forming  the  chief  mass  of  the  rocks  of  the  earth's  crust  (p.  6).  As 
the  metals  can  be  obtained  from  these  sificates  only  with  difficulty, 


POTASSIUM.  201 

they  are  not  used  for  the  preparation  of  the  metals,  but  other  com- 
pounds, occurring  to  a  less  extent,  are  used  for  this  purpose. 

Preparation.  1.  The  native  metals  are  separated  from  the  accom- 
panying rock  formation  by  fusion  (bismuth),  by  washing  (gold),  or 
by  distillation  (mercury). 

2.  The  metals  are  obtained  from  their  ores  by  various  compHcated 
methods. 

The  metallic  oxides  are  mostly  reduced  by  heating  with  carbon. 
This  can  be  done  in  the  case  of  the  oxides  of  the  rare  metals  by  the 
action  of  the  electric  arc  or  by  aluminium  (which  see). 

Metallic  sulphides  are  either  converted  into  oxygen  compounds 
by  heating  them  in  the  air  (roasting)  and  then  reduced  by  carbon,  or 
they  are  heated  with  some  cheaper  metal  which  sets  the  contained 
metal  free  (precipitation). 

Many  ores  are  dissolved  and  then  precipitated  from  their  solution 
by  cheaper  metals  or  by  the  electric  current.  Thus  metallic  copper  Is 
precipitated  from  a  solution  of  copper  sulphate  by  iron,  while  the  iron 
is  dissolved  as  ferrous  sulphate. 

3.  The  hght  metals  (see  above),  as  they  can  only  be  separated 
from  their  widely  distributed  sihcates  with  difficulty,  are  obtained  on 
a  large  scale  from  their  chlorides  by  electrolysis,  or  to  a  less  extent 
by  heating  the  chlorides  with  sodium,  or  from  their  oxides  by  heating 
with  aluminium. 

ALKALI  METAL  GROUP. 

Lithium.     Sodium.     Potassium.     Rubidium.     Caesium  (Ammonium), 

Monovalent  metals,  soft  at  ordinary  temperatures,  readily  fusible  and 
volatile  on  heating  strongly.  They  oxidize  even  at  ordinary  temperatures, 
decompose  water  rapidly  in  the  cold,  and  then  form  hydroxides  (the  alka- 
lies) which  are  very  soluble  in  water  and  volatile  without  decomposition 
at  high  temperatures  and  are  the  strongest  bases.  Their  carbonates, 
sulphates,  phosphates,  and  sulphides  are  soluble  in  water,  while  the  car- 
bonates and  phosphates  of  all  other  metals  are  insoluble  in  water. 

I.  Potassium  (Kalium). 

Atomic  weight  39.15==K. 

Occurrence.  Only  combined.  Potassium  chloride  and  potassium 
sulphate  occur  in  sea-water,  and  besides  this  they  form  large  deposits, 
generally  above  rock  salt,  in  North  Germany  and  Galicia.     These 


202  INORGANIC  CHEMISTRY. 

"abraum  salts"  (so  called  from  the  German  word  ahraumen,  to 
remove,  because  it  must  first  be  removed  to  get  at  the  rock  salt), 
which  were  formerly  obtained  only  at  Stassfurt  (Germany),  contain 
especially  the  potassium  salts  carnallite  and  sylvine  (p.  204)  and 
kainite  and  schonite  (p.  206),  which  are  valuable  fertilizers  (potash 
fertilizers),  and  form  the  original  substance  from  which  many  other 
potassium  salts  are  prepared. 

Potassium  is  also  widely  distributed  as  a  constituent  of  many 
varieties  of  rock,  especially  as  potassium-aluminium  silicate;  thus 
as  feldspar,  leucite,  and  mica,  which  undergo  weathering  and  supply 
potassium  compounds  to  the  soil,  these  being  taken  up  by  the  plants 
and  remain  in  the  ash,  after  burning  of  the  plants.  The  potassium 
compounds  are  introduced  into  the  animal  organism  by  means  of 
the  plants  and  are  found  especially  in  the  muscles,  blood  corpuscles, 
eggs,  and  in  milk. 

*  Preparation.  1.  By  the  electrolysis  of  fused  potassium  hydroxide, 
potassium  chloride,  or  potassium  cyanide,  when  the  potassium  sepa- 
rates at  the  negative  pole,  or  by  the  electrolysis  of  an  aqueous  solu- 
tion of  potassium  chloride,  using  mercury  as  the  negative  pole,  when 
the  potassium  which  is  set  free  does  not  decompose  the  water  but 
forms  an  amalgam  with  the  mercury  from  which  it  is  separated  by 
heating  to  360°. 

2.  By  heating  an  intimate  mixture  of  potassium  carbonate  with 
carbon:  K2C03+2C=2K4-3CO.  The  potassium  volatilizes  and  the 
vapors  are  condensed  in  flat  iron  boxes,  which  when  filled  are  cooled 
in  petroleum. 

The  potassium  vapors  used  to  be  condensed  by  conducting  the  vapors 
directly  into  petroleum.  In  this  case  a  part  of  the  potassium  combined 
with  the  carbon  monoxide,  forming  a  black  and  very  explosive  compound 
(COK)e  (p.  189). 

Properties.  Shining,  siiver-white  metal  which  is  as  soft  as  wax 
and  brittle  at  0°.  It  has  a  specific  gravity  0.86,  melts  at  62.5°  and 
distils  as  a  greenish-blue  vapor  at  about  670°.  It  quickly  oxidizes  in 
moist  air,  the  surface  being  covered  with  potassium  hydroxide;  hence 
it  is  kept  in  petroleum.  When  fused  in  the  air  it  inflames  and  burns 
with  a  violet  flame  into  not  well-known  oxides.  It  decomposes  water 
with  the  formation  of  potassium  hydroxide  and  hydrogen,  whereby 
considerable  heat  is  evolved  so  that  it  inflames  the  hydrogen  which 


POTASSIUM.  203 

burns  with  a  violet  flame  due  to  the  volatiHzed  potassium,  2K  + 
2H20=2KOH+2H;  when  alloyed  with  mercury  it  decomposes  water 
without  the  production  of  flame.  It  combines  directly  with  the  halo- 
gens, sulphur,  and  phosphorus,  with  the  productionof  flame,  and  when 
heated  with  hydrogen  to  400°  it  combines,  forming  silver-hke  brittle 
potassium  hydride,  KjH,  which  spontaneously  inflames  in  the  air  and 
which  decomposes  at  about  420°.  On  account  of  its  relationship  to 
oxygen  and  chlorine  potassium  is  used  in  the  setting  free  of  metals 
from  their  oxygen  and  chlorine  compounds. 

a.  Compounds  of  Potassium. 

Potassium  oxide,  K2O,  is  not  known  with  certainty. 

Potassium  Hydroxide,  Caustic  Potash,  KOH. 

Formation.     1.  By  the  action  of  potassium  on  water  (see  above). 

Preparation.  1.  On  a  large  scale  by  the  electrolysis  of  an  aque- 
ous solution  of  potassium  chloride:  KC1+H20  =  K0H+H+C1. 

2.  In  smafl  quantities  by  boiling  a  solution  of  potassium  car- 
bonate with  slaked  lime  (calcium  hydroxide);  insoluble  calcium 
carbonate  settles  out  and  the  solution  contains  potassium  hydroxide: 
K2C03+Ca(OH)2  =  CaC03+2KOH.  The  solutions  obtained  in  1  and 
2  are  evaporated  in  silver  dishes,  as  the  KOH  acts  upon  iron  and 
porcelain. 

Properties.  White,  crystalline  substance,  the  strongest  of  all 
bases,  fusible  at  a  red  heat,  and  volatile  without  decomposition  at 
higher  temperatures.  When  exposed  to  the  air  it  absorbs  moisture 
and  deUquesces  and  at  the  same  time  absorbing  carbon  dioxide. 
It  destroys  most  plant  and  animal  substances  and  is  therefore  used 
as  a  caustic  agent.  It  is  very  soluble  in  water  and  alcohol;  the  alco- 
holic solution  is  called  alcoholic  potash.  As  these  solutions  contain 
one  of  the  strongest  bases  they  precipitate  most  metals  as  hydroxides 
or  oxides  from  their  solution;  thus,  FeS04+2KOH  =  Fe(OH)2+K2S04. 

'  Potassium  sulphide,  potassium  sulphuret,  KgS,  is  obtained  by  fusing 
potassium  sulphate  with  carbon,  as  an  anhydrous,  dark -red,  crystalline 
mass:  K2S04  +  2C=K2S  +  2C02.  It  is  very  hygroscopic,  has  an  alkaline 
reaction,  absorbs  oxygen  and  water  from  the  air,  and  is  converted  into 
potassium  thiosulphate  and  potassium  hydroxide: 

2K2S  +  H2O  +  40 = K2S2O3 + 2K0H. 


204  INORGANIC  CHEMISTRY. 

On  mixing  a  watery  solution  of  potassium  hydrosulphide  with  a  so- 
lution of  potassium  hydroxide  we  obtain  a  solution  of  the  sulphide 
from  which  colorless  crystals  of  KgS  +  SHgO  separate  on  evaporation: 
KSH  +  KOH  =  KgS  +  H2O.     With  acids  it  develops  HgS : 

KgS  +  H2S0,=  K2SO,  +  H^S. 

Potassium  hydrosulphide,  potassium  sulphydrate,  KSH,  is  obtained  in 
solution  by  saturating  caustic  potash  with  HgS :  KOH  +  H2S=  KSH  +  HgO. 
On  carefully  evaporating  this  solution  we  obtain  alkaUne,  colorless  crystals 
having  the  formula  2KSH  +  H2O,  which  on  heating  lose  their  water  and 
anhydrous  KSH  is  obtained  as  a  yellow  mass.  With  acids  it  generates 
HoS,  with  sulphoacids  or  their  anhydrides  it  combines  (like  its  anhydride 
K2S),  producing  sulphosalts;  thus,  6KSH  +  As2S3=  2K3ASS3  +  SHgS : 

K2S  +  CS2=K2CS3(p.  193). 

Potassium  Polysulphides.  Besides  the  sulphides  K2S  and  KSH 
we  have  the  polysulphides  .or  polysulphurets,  K2S2,  KjSg,  K2S4,  KjSs^ 
which  are  obtained  by  fusing  potassium  monosulphide,  KjS,  with  a 
corresponding  amount  of  sulphur.  They  form  red  or  yellow  masses 
which  are  readily  soluble  in  water  and  are  decomposed  by  acids  with 
the  development  of  HgS  and  at  the  same  time  finely  divided,  nearly- 
white  sulphur,  so-called  milk  of  sulphur  (p.  121)  separates: 

K2S3+  H2SO4  =  K2SO4+  H2S+  2S. 

Liver  of  sulphur,  hepar  sulfuris,  is  the  mixture  of  potassium 
polysulphides  with  potassium  thiosulphate  or  potassium  sulphate 
obtained  by  heating  potassium  carbonate  with  sulphur.  It  is  deli- 
quescent, readily  soluble  in  water,  and  forms  masses  which  have  a 
brown  color  (hence  the  name). 

Potassium  Chloride,  KCl.  Occurs  a  ssylvine,  KCl,  as  carnallite 
(MgCl2+KCl+6H20),  also  in  sea-water,  in  certain  salt  springs,  and 
in  the  ash  of  plants,  in  animal  fluids  and  tissues. 

Preparation.  It  crystallizes  directly  from  a  hot  saturated  solution 
of  carnallite  on  cooling  and  is  also  formed  by  the  action  of  hydro- 
chloric acid  upon  potassium  hydroxide  or  carbonate:  K2C03+2HC1  = 
2KC1+ H2O+ CO2.  It  forms  colorless,  shining  cubes  which  melt  at 
a  red  heat  and  are  volatile  at  a  white  heat.  These  crystals  dissolve 
in  3  parts  water. 

Potassium  Bromide,  KBr.  Preparation.  By  dissolving  bromine 
in  caustic  potash,  when  potassium  bromide  and  potassium  bromate  are 
formed :  6Br+  6K0H  =  5KBr+  KBrOs^-  3H2O.  This  is  evaporated  to 
dryness  and  heated  with  carbon  when  the   potassium    bromate  is 


POTASSIUM.  205 

reduced  to  bromide :  KBr03+  3C  =  KBr+  3C0.  On  dissolving  this  in 
water,  filtering  and  evaporating  to  crystallization,  we  obtain  the 
crystals. 

Properties,  Colorless,  shining  cubes  which  are  fusible  and  volatile 
and  soluble  in  three  parts  of  water. 

Potassium  iodide,  KI,  is  obtained  in  an  analogous  manner  to 
potassium  bromide. 

Iodine  is  rubbed  with  considerable  powdered  iron  under  water,  when 
ferrous  iodide  is  formed  and  enough  iodine  is  added  to  this  solution  until 
ferrous-ferric  iodide,  Fe2l8(2Fel3+Fel2),  is  formed.  This  solution  is 
now  treated  with  an  equivalent  quantity  of  potassium  carbonate  and 
heated  to  boiling,  when  ferrous-ferric  oxide  precipitates  and  the  dissolved 
KI  obtained  by  evaporation  to  crystallization: 

Fcglg  +  4K2C03=  FcgO^  +  8KI  +  4CO2. 

Properties.  It  forms  colorless  cubes  which  are  fusible  and  volatile 
and  soluble  in  0.75  part  water.  Aqueous  solutions  of  potassium  iodide 
dissolve  iodine  readily,  and  many  iodine  compounds  which  are  insol- 
uble in  water,  such  as  Hglj,  are  also  soluble  therein. 

Potassium  Chlorate,  KCIO3.  Preparation..  1.  Besides  KCl  by 
passing  chlorine 'into  a  hot  concentrated  caustic  potash  solution  and 
by  evaporating  this  to  crystallization  when  the  more  insoluble  potas- 
sium chlorate  separates  out  first  (p.   138). 

2.  It  is  prepared  on  a  large  scale  as  follows :  Warm  milk  of  lime, 
Ca(0H)2,  is  saturated  with  chlorine  and  the  calcium  chlorate  formed 
is  treated  with  potassium  chloride,  Ca(C103)2-H2KCl=CaCl2+2KC103, 
or  by  the  electrolysis  of  potassium  chloride  (p.  104) ,  when  the  chlorine 
set  free  at  the  anode  is  passed  directly  into  the  potassium  hydroxide 
formed  at  the  cathode. 

Properties.  Colorless  plates  having  a  characteristic  cooling 
taste,  soluble  in  16  parts  cold  water  and  melting  at  334°.  On  heat- 
ing above  this  point  it  decomposes  into  potassium  chloride  and 
potassium  perchlorate,  and  oxygen  is  given  off  (p.  139).  On  heating 
still  higher  all  the  oxygen  is  expelled  and  it  is  converted  into  potas- 
sium chloride.    In  regard  to  other  properties  of  the  chlorate  see  p.  138. 

Potassium  Perchlorate,  KCIO4.  It  is  prepared  as  described  on  p.  139, 
and  occurs  often  to  a  slight  extent  in  Chili  saltpeter,  and  forms  colorless 
crystals  which  are  very  insoluble  in  water  and  hence  is  readily  freed  from 
the  potassium  chloride  produced  in  its  preparation  by  washing  with 
water. 

Potassium  hypochlorite,  KCIO,  is  known  only  as  a  watery  solution 
(eau  de  Javelle)  and  is  used  as  a  bleaching  agent,  especially  for  wine- 


206  INORGANIC  CHEMISTRY. 

and  fruit-stains.  See  p.  137  for  further  information  in  regard  to  hypo- 
chlorites. 

Potassium  sulphate,  secondary  potassium  sulphate,  KgSO^,  occurs  in 
the  lava  of  Vesuvius  and  in  schonite  (K2SO4  +  MgSO<  +  GHgO)  and 
kainite  (KgSO^  +  MgS04  +  MgClg  +  GHgO) ;  also  in  most  plants  and  to  a 
slight  extent  in  the  urine  and  blood.  It  is  obtained  by  heating  potassium 
chloride  with  sulphuric  acid,  2KC1  +  H2S0,=  K2S04  +  2HC1,  and  also 
commercially  from  kainite  and  schonite.  It  forms  white,  hard  crystals 
or  crystalline  crusts  which  melt  at  a  red  heat  without  decomposition  and 
are  soluble  in  10  parts  cold  water. 

Potassium  bisulphate,  potassium  acid  sulphate,  primary  potassium 
sulphate,  KHSO4,  occurs  as  misenite  and  is  obtained  as  a  by-product  in 
the  chemical  industries  or  by  dissolving  potassium  sulphate  in  sulphuric 
acid:    K2S04  +  H2SO,=  2KHSO,. 

It  forms  colorless  acid  crystals,  readily  soluble  in  water  and  readily 
fusible.  On  heating  somewhat  above  its  melting-point  (197°)  it  forms 
potassium  pyrosulphate,  K2S2O7  (p.  130):  2KHS04=K2S207  +  H20.  On 
heating  higher  it  decomposes  into  potassium  sulphate  and  sulphur  tri- 
oxide:  K2S20,=  K2S04  +  S03.  As  this  decomposition  takes  place  at 
about  600°  acid  potassium  sulphate  is  used  in  decomposing  minerals  which 
are  not  attacked  by  sulphuric  acid  at  its  melting-point  (338°). 

Potassium  persulphate,  K2S20g,  is  produced  in  the  electrolysis  of  a 
watery  solution  of  potassium  bisulphate  and  forms  a  white  crystalline 
powder.     (Properties,  see  p.  131.) 

Potassium  Nitrate,  Saltpeter,  KNO3.  Occurrence.  To  a  con- 
siderable extent  in  the  soil  in  warm  climates  (Bengal,  India)  and  to 
a  less  extent  in  nearly  every  arable  soil.  Its  formation  depends 
upon  the  fact  that  when  nitrogenous  organic  matter  suffers  decay  in 
the  air  and  in  the  presence  of  strong  bases  the  micro-organisms  oxi- 
dize the  nitrogen  into  nitric  acid  (p.  161).  So-called  wall  saltpeter, 
which  forms  in  stables  and  closets,  is  calcium  nitrate. 

Preparation.  1.  It  was  formerly  prepared  according  to  the  fol- 
lowing process:  Animal  refuse  is  piled  up  with  rubbish,  wood 
ashes,  or  other  bodies  rich  in  potassium  and  then  moistened  with 
urine  and  liquid  manure  (saltpeter  plantation).  After  2  or  3  years 
the  saltpeter  effloresces  out  and  is  'scraped  off,  dissolved  in  water, 
and  treated  with  potassium  carbonate  in  order  to  decompose  any  cal- 
cium nitrate  present.     It  is  obtained  pure  by  repeated  crystallization. 

2.  By  purifying  the  natural  potassium  nitrate  by  repeated  recrys- 
tailization. 

3.  Hot  concentrated  solutions  of  Chili  saltpeter  (NaNOg,  p.  212) 
and  the  potassium  chloride  obtained  from  Stassfurt  salt  are  mixed: 
NaN03-fKCl=NaCl+KN03.  The  sodium  chloride  is  about  as  solu- 
ble in  cold  water  as  in  warm,  so  it  remains  in  solution  on  cooling  the 


POTASSIUM.  207 

same,  while  the  less  soluble  potassium  nitrate  separates  out  on  cooling 
(conversion  saltpeter). 

Properties.  Colorless  prisms  or  crystalline  powder,  soluble  in  4 
parts  cold  water  and  in  less  than  one-half  its  weight  of  hot  water. 
It  is  nearly  insoluble  in  alcohol,  melts  at  340°,  and  on  further  heating 
it  yields  oxygen  and  forms  potassium  nitrite,  KNOj,  and  finally 
decomposes  into  potassium  oxide,  nitrogen,  and  oxygen  and  hence 
has  an  active  oxidizing  action  (p.  159).  Paper  impregnated  with 
potassium  nitrate  is  called  touch-paper  (charta  nitrata)  and  is  used 
in  medicine. 

Gunpowder  is  a  granular  mixture  of  about  75  per  cent,  saltpeter  and 
12.5  per  cent,  each  of  sulphur  and  wood  charcoal.  One  gram  powder 
yields  260  c.c.  explosion  gases,  measured  at  0°  and  760  mm.  pressure, 
which  with  heat  set  free  at  the  time  of  the  explosion  expands  to  2100  c.c. 
The  decomposition  takes  place  theoretically  as  follows:  2KN03+S  +  3C= 
KgS  +  2N  +  SCOg.  As  a  matter  of  fact  the  decomposition  is  more  compli- 
cated. 

Potassium  nitrite,  KNOg,  is  obtained  by  heating  saltpeter  (which  see) 
or  by  melting  the  same  with  lead.  It  forms  a  colorless  deliquescent 
salt,  which  is  readily  soluble. 

Potassium  arseriite,  KgAsOg,  is  obtained  by  neutralizing  a  solution 
of  arsenious  acid  with  KgCOg.  A  watery  solution  containing  1  per  cent. 
AsgOg  as  KgAsOg  is  called  Fowler's  solution. 

Potassium  Carbonate,  Potash,  K2CO3.  Preparation.  1.  In  coun- 
tries rich  in  forests  the  ashes  of  the  trees  are  lixiviated  with  water 
and  the  filtered  solution  evaporated  to  dryness  and  the  brown  residue 
heated  until  white. 

Land  plants  contain  sodium,  calcium,  magnesium,  and  especially 
potassium,  which  are  combined  with  organic  acids,  sulphuric  acid,  phos- 
phoric acid,  and  chlorine.  On  burning  the  organic  salts  are  converted 
into  carbonates. 

2.  From  the  fat-free  wash-water  from  wool  by  evaporation, 
ashing,  lixiviation,  etc.,  as  described  in  method  1. 

3.  From  the  residue  remaining  after  the  obtainment  of  alcohol  from 
beet-root  molasses,  which,  unlike  the  residue  left  after  the  prepara- 
tion of  alcohol  from  potatoes,  has  no  value  as  a  food  for  animals. 
The  residue  is  ashed  and  Uxiviated  and  treated  as  given  in  method  1. 

The  crude  potash  (calcined  potash)  obtained  by  methods  1,2,  and 
3  contain  up  to  10  per  cent,  foreign  salts,  especially  potassium  chloride. 

4.  It  is  prepared  in  greatest  quantities  from  potassium  chloride 
of  "abraum"  salts  in  an  analogous  manner  to  sodium  carbonate 
from  sodium  chloride  (p.  213)  or  by  saturating  a  mixture  of  magnesium 


208  INORGANIC  CHEMISTRY. 

carbonate  and  potassium  chloride  solution  with  COj  when  the  insolu- 
ble double  salt  MgCOgH- KHCO3+ 4H2O  separates  out.  On  heating 
this  with  water  under  pressure  it  decomposes  into  insoluble  magne- 
sium carbonate  and  potassium  carbonate,  which  remains  in  solution 
and  which  is  obtained  therefrom  by  evaporation. 

The  purified  potash  thus  obtained  still  contains  a  small  percentage 
of  foreign  salts.  Such  potash  is  also  obtained  by  dissolving  crude 
potash  (pearlash)  in  a  small  quantity  of  water,  which  leaves  the 
impurities  in  part  undissolved,  and  then  evaporating  the  solution, 
when  at  first  the  less  soluble  foreign  salts  separate  and  on  further 
evaporation  the  pure  potash  results. 

Potash  was  formerly  obtained  by  heating  tartar  (see  Tartaric  acid), 
when  potassium  carbonate  and  carbon  were  derived;  hence  pure  potash 
is  sometimes  called  salt  of  tartar  or  sal.  tartari.  It  can  also  be  obtained 
by  heating  potassium  bicarbonate,  which  can  be  readily  prepared  pure: 
2kHC03  +  K2CO3  +  H2O  +  CO2. 

Properties.  White,  granular,  strongly  alkaline  powder  which 
melts  at  a  high  temperature  without  decomposition  and  is  soluble  in 
equal  parts  of  water,  and  can  be  obtained  from  this  solution  as  color- 
less crystals,  2K2CO3+  SHjO,  on  evaporation.  It  deliquesces  in  the  air 
to  a  thick  liquid,  due  to  its  absorbing  water. 

Primary  Potassium  Carbonate,  KHCO3,  Potassium  Bicarbonate 
or  Acid  Carbonate.  If  carbon  dioxide  is  passed  into  a  concentrated 
solution  of  potassium  carbonate  the  acid  salt  crystallizes  out  as  color- 
less transparent  crystals  because  of  the  less  solubility  of  this  salt: 
K2C03+H20+C02  =  2KHC03.  This  salt  is  soluble  in  4  parts  water 
and  is  alkaline  in  reaction. 

Potassium  silicate,  potassium  water-glass,  is  obtained  by  fusing 
potassium  carbonate  with  sand  (Si02,p.  196)  as  a  vitreous  mass,  which 
has  no  constant  constitution  but  is  a  mixture  of  various  polysilicates 
(p.  197).  When  powdered  it  is  soluble  in  water  on  boiling  for  a  long 
time;  the  concentrated  aqueous  solution  soon  solidifies  in  the  air 
and  after  a  time  dries  to  a  non-transparent  mass. 

h.  Detection  of  Potassium  Compounds. 

1.  They  give  a  violet  coloration  to  the  non-luminous  flame.  The 
spectrum  of  this  flame  is  characterized  by  a  red  and  a  violet  line. 

2.  Platinum  chloride  produces  a  yellow  crystalline  precipitate 
of  potassium-platinum  chloride,  KjPtCle. 


J 


SODIUM.  209 

3.  Tartaric  acid  produces  a  gradual  precipitate  of  white  crystalline 
potassium  acid  tartrate,  C4H5KO6  (cream  of  tartar). 

4.  Sodium  picrate  precipitates  yellow  crystalline  potassium 
picrate,  CgHjCNOJaCOK),  from  potassium  salt  solutions. 

Reactions  2,  3,  and  4  are  also  given  by  ammonium  salts,  but  these 
volatilize  when  gently  heated  and  hence  can  be  separated  in  this  way. 

2.  Sodium  (Natrium). 

Atomic  weight  23.05  =  Na. 

Occurrence.  Only  combined,  abundantly  and  widely  distributed, 
especially  as  sodium  chloride,  as  enormous  deposits  (rock  salt),  as 
well  as  in  solution  in  sea-water,  in  various  salt  seas  or  lakes  and  springs. 
Sodium  nitrate  occurs  deposited  in  South  America  as  Chili  saltpeter, 
while  sodium  silicate  is  a  constituent  of  many  minerals  and  crystalhne 
rocks.  Traces  of  sodium  salts  are  always  found  in  the  atmospheric 
dust. 

Sodium  is  very  widely  distributed  in  the  plant  kingdom;  still 
potassium  compounds  exist  to  a  greater  extent  in  land  plants.  The 
sodium  salts  are  extensively  distributed  in  the  animal  kingdom,  and 
especially  in  the  fluid  parts  of  the  body,  while  the  potassium  salts 
exist  to  a  greater  extent  in  the  solid  parts. 

Preparation.  Sodium  is  prepared  in  the  same  way  as  potassium. 
Sodium  does  not  form  an  explosive  compound  with  carbon  monoxide  in 
its  preparation  from  sodium  carbonate  and  carbon  (see  p.  202). 

Properties.  Shining  white,  soft  metal  havinf^  a  specific  gravity  of 
0.97,  melting  at  95.6°,  and  volatile  at  742°,  forming  a  colorless  vapor. 
It  quickly  oxidizes  in  the  air,  hence  it  is  kept  beneath  petroleum. 
It  burns  on  warming  with  a  yellow  flame  into  Na202  and  decomposes 
water  like  potassium ;  still  the  heat  produced  is  not  sufficient  to  ignite 
the  hydrogen.  With  hydrogen  it  forms  silvery-white  sodium  hy- 
dride, NagH,  which  does  not  spontaneously  inflame. 

a.  Compounds  of  Sodium. 

Sodium  oxides  and  Sodium  sulphides  have  analogous  constitution 
and  sifmilar  properties  to  the  corresponding  potassium  compounds  and 
are  prepared  in  the  same  way. 

Sodium  hydroxide,  NaOH,  caustic  soda,  is  prepared  in  a  similar 
manner  to  potassium  hydroxide  (see  also  Sodium  Carbonate)  and  has 
the  same  properties.  When  impure  it  occurs  in  commerce  as  white, 
bluish,  or  reddish  pieces. 

Sodium  peroxide,  NajOg,  produced  by  passing  air  over  heated  metallic 


j  210  INORGANIC  CHEMISTRY. 

sodium.  It  forms  white  or  yellowish  crystalline  masses  which  with  ice- 
cold  water  forms  NaOH  and  H^C)^,  and  with  water  at  ordinary  tempera- 
ture generates  oxj^gftn  and  NaOH.  It  has  energetic  oxidizing  properties, 
often  with  explosive  violence. 

Sodium  Chloride,  Common  Salt,  NaCl.  Occurrence,  In  enormous 
layers  as  rock  salt,  dissolved  in  sea-water  (up  to  3  per  cent.),  and  in 
many  springs,  the  salt  springs.  It  is  a  constituent  of  plant-ashes 
and  occurs  in  all  fluids  of  the  animal  body,  especially  in  the  blood 
and  urine. 

Preparation.  1.  From  rock  salt,  which  is  often  found  very  pure, 
sometimes  in  regular  cubes,  but  mostly  as  transparent  masses.  If  it 
contains  foreign  salts  (clay,  gypsum),  it  is  dissolved  in  water  in  the  mine 
and  the  solution  (salt  brine)  pumped  to  the  surface  of  the  earth  and 
evaporated  until  crystallization  occurs.  , 

2.  From  sea-water.  In  hot  climes  the  sea-water  is  allowed  to  evapo- 
rate to  crystallization  in  flat  basins  ("salterns")  by  means  of  the  summer 
heat.  In  cold  cUmes  the  sea-water  is  allowed  to  freeze  in  the  salterns  : 
the  ice  formed  consists  only  of  water,  and  on  removal  a  concentrated 
brine  solution  is  obtained,  which  is  evaporated  to  crvstallization. 

3.  In  Germany,  where  the  climate  is  not  suitable  lor  the  evaporation 
of  sea-water  and  as  most  of  the  brine  springs  would  renuire  considerable 
fuel  for  evaporation,  the  salt  solutions  are  concentrated  by  spontaneous 
evaporation.  The  solutions  are  allowed  to  trickle  repeatedly  drop  by 
drop  through  bundles  of  fagots  piled  up  together  and  exposed  to  the 
prevailing  winds  (graduation-house).  During  the  "graduation"  the 
insoluble  impurities,  such  as  calcium  sulphate,  calcium  and  magnesium 
carbonate,  attach  themselves  to  the  twigs.  .The  concentrated  brine  is 
then  evtiporatcd,  when  more  of  the  above-mentioned  insoluble  salts 
with  NaCl  separate  out,  called  pan-stone  (lick-salt  for  animals).  On 
further  evaporation  the  pure  salt  then  deposits.  The  mother-liquor 
contains  the  more  soluble  salts,  such  as  calcium  and  magnesium  bromides. 

Properties.  Large,  colorless  cubes  or  smaller,  hollow,  step-like 
pyramids,  or  hopper-shaped  crystals,  or  a  crystalline  powder.  They 
melt  at  red  heat  and  are  volatile  at  white  heat.  Hardly  more  soluble 
in  hot  water  than  in  cold  water;  100  ])arts  water  at  0°  dissolve  36 
parts  and  at  100°  39  parts  salt.  At  various  temperatures  during 
evaporation  of  the  brine  we  obtain  fine  salt,  coarse  salt,  or  medium  salt. 
If  salt  becomes  moist  in  the  air,  it  contains  magnesium  salts. 

Sodium  iodide,  Nal,  and 

Sodium  bromide,  NaRr,  are  obtained  in  the  same  manner  •  as  the 
corresponding  ])()iMssiuni  salt  and  have  the  same  properties. 

Sodium  hypochlorite,  NaClO,  is  known  only  in  solution  (eau  de 
Lal)arra<iuc). 

Sodium  sulphite,  Na.S0;,4  THjO,  is  obtained  bv  the  action  of  SO, 
upon  sodium  hydrate  solution  (see  Sulphites,  p.  126). 

Sodium  bisulphite,  NaHSOg,  gives  off  SOa  in  the  air  and  is  oxidized  to 
Naj,S04. 


SODIUM.  211 

Sodium  Sulphate,  Na2S04,  Glauber  Salts.  Occurrence.  In  many 
mineral  waters  (Carlsbad,  Marienbad),  salt  springs,  sea-water,  and 
in  Spain  as  enormous  deposits. 

Preparation.  1.  On  an  extensive  scale  by  heating  sodium  chloride 
with  sulphuric  acid  in  the  manufacture  of  soda  (p.  213)  and  hydro- 
chloric acid  (p.  135): 

2NaCl+  H2SO4  =  Na2S04+  2HC1. 

2.  By  decomposing  dissolved  magnesium  sulphate  (kieserite) 
with  sodium  chloride:  MgS04+ 2NaCl  =  MgCl2+ Na^SO^. 

This  process  is  only  accomplished  at  low  temperatures,  and  is  per- 
formed at  Stassfurt  during  wmter.  The  MgCl2  produced  remains  in 
Bolution,  while  Na2S04  crystallizes  out. 

3.  By  passing  sulphur  dioxide,  air,  and  steam  over  heated  sodium 
chloride  (Hargreave's  process):    2NaCl  +  S02  +  0  +  H20=Na2SO,  +  2HCl. 

Properties.  Colorless  prisms  of  the  composition  Na2SO4+10H2O 
or  containing  56  per  cent,  water.  On  lying  in  the  air  they  lose  a 
part  of  their  water  of  crystallization  and  then  become  cloudy  and 
non-transparent. 

Sodium  sulphate  melts  at  33°  and  decomposes  into  a  saturated  solu- 
tion and  into  anhydrous  Na^SO^.  On  further  heating  it  loses  its 
water  of  crystallization  completely  and  is  converted  into  anhydrous 
Na^SO^. 

100  parts  water  at  18°  dissolves  20  parts,  at  30°  200  parts,  and  at  33° 
354  parts  of  the  salt  Na2SO4  +  10H2O.  Above  33°  the  solubility  dimin- 
ishes, at  50°  only  263  parts  are  dissolved,  at  100°  238  parts  of  the  salt. 
This  depends  upon  the  fact  that  at  33°  the  anhydrous  salt  NajSO^  is 
formed  and  separates  out,  and  at  the  same  time  a  part  of  it  as  such  goes 
again  into  solution,  so  that  a  condition  is  obtained  where  its  solubility 
diminishes  in  increasing  temperatures.  If  a  solution  which  is  saturated 
at  33°  is  cooled  to  a  lower  temperature,  no  salt  separates  out,  although 
the  salt  is  less  soluble  therein  (supersaturated  solution,  p.  52). 

Dry  sodium  sulphate,  Na2S04  +  H20,  is  obtained  by  drying  sodium 
sulphate. 

Artificial  Carlsbad  salt  is  a  mixture  of  sodium  sulphate,  sodium 
carbonate,  sodium  chloride,  and  potassium  sulphate. 

Sodmm  thiosulphate,  Na^SaO^,  sodium  hyposulphite,  is  obtained 
from  the  soda  residues  or  bv  boiline  an  aqueous  solution  of  sodium  sul- 
phite with  flowers  of  sulphur:  Na2S03  +  S=Na^S203.  It  crystallizes 
with  5  molecules  of  H2O  in  prisms  which  are  stable  in  the  air  and  are 
readily  soluble.  The  solution  is  decomposed  by  acids  with  the  setting 
free  of  sulphur  Cmilk  of  sulphur,  p.  121)  and  sulphur  dioxide:  NajSaO^^- 
2HCl=2NaCl  +  S02  +  S  +  H20.  It  has  a  reducing  action  converting 
chlorine,  bromine,  and  iodine  into  sodium  salts:  2Na2S203  4-2I=2NaI  + 
Na2S40R  Csodium  tetrathionate,  p.  124)  and  hence  serves  as  "antichlor" 
in   chlorine  bleaching   in   order  to   remove   the   excess  of   chlorine.     It 


212  INORGANIC  CHEMISTRY, 

dissolves  the  halogen  salts  of  silver  and  is  used  in  photography  as  a  "fixing 
salt,"  removing  the  silver  compounds  not  acted  upon  by  light. 

Sodium  Nitrate,  Chili  saltpeter,  NaNOj,  occurs  in  large  deposits 
in  ChiH,  from  whence  the  world  receives  its  supply,  using  it  to  a  great 
extent  as  a  fertilizer.  It  is  purified  by  recrystallization  and  forms 
colorless  rhombohedric  anhydrous  crystals  soluble  in  1.2  parts 
water.  The  crystals  are  cubical,  hence  the  salt  is  called  cubical  salt- 
peter. It  deliquesces  in  the  air,  hence  it  cannot  be  used  in  the  manu- 
facture of  gunpowder. 

Tertiary  sodium  phosphate,  Na3P04,  trisodium  phosphate,  so-called 
basic  sodium  phosphate  (p.  169),  is  obtained  by  treating  the  secondary 
sodium  phosphate  with  NaOH  and  evaporating  to  crystallization,  it 
forms  colorless,  strongly  alkaline  prisms,  Na3P04  +  12H20. 

Secondary  sodium  phosphate,  NagHPO^,  disodium  phosphate,  so- 
called  neutral  sodium  phosphate  (p.  169),  occurs  in  carnivorous  urine  and 
other  animal  fluids,  and  is  obtained  by  saturating  phosphoric  acid  with 
NaOH  until  a  faint  alkaline  reaction  is  obtained  and  then  evaporating 
to  crystallization.  It  forms  colorless,  readily  efflorescing,  faintly  alka- 
line prisms,  Na2HP04+ I2H2O,  which  are  soluble  in  5.8  parts  water.  On 
heating  it  fuses  in  its  water  of  crystallization,  then  loses  this  and  is  con- 
verted into   sodium    pyrophosphate:     2Na2HP04=Na4P207  +  H20. 

Primary  sodium  phosphate,  NaH2P04,  monosodium  phosphate, 
so-called  acid  sodium  phosphate  (p.  169),  occurs  in  carnivorous  urine 
and  gives  the  acid  reaction  to  the  same.  It  is  obtained  when  phosphoric 
acid  is  treated  with  a  calculated  amount  of  NaOH  and  evaporated.  It 
forms  colorless  acid  crystals,  NaH2P04  +  H20.  It  loses  its  water  of  crys- 
tallization at  100°,  and  on  heating  more  intensely  acid  sodium  pyrophos- 
phate, NajHgPaOy,  and  finally  sodium  metaphosphate,  NaPOg,  is  obtained: 

2NaH2P04=  Na2H2P207  +  H2O ;  Na2H2P207=  2NaP03 + B,0. 

This  last  is  used  in  blowpipe  analysis  like  borax  (see  below). 

Sodium  sulphantimonate,  Na3SbS4  +  9H20  (Schlippe's  salt),  is  obtained 
by  boiling  antimony  trisulphide  with  sulphur  and  caustic  soda,  or,  instead 
of  the  latter,  with  soda  solution  and  lime.  It  crystallizes  in  colorless 
tetrahedra,  soon  becoming  pale  yellow,  and  is  used  in  the  preparation  of 
gold  sulphur  (p.  181)  : 

2Na3SbS4  +  6HC1=  6NaCl  +  Sb2S5  +  3H2S. 

Sodium  Tetraborate,  Na2B407+ lOHjO,  sodium  biborate,  borax, 
occurs  dissolved  in  certain  lakes  of  California  and  Thibet,  and  occurs  in 
commerce  as  tinkal.  It  is  obtained  at  the  present  time  by  satu- 
rating a  solution  of  boracic  acid  with  soda  and  recrystallizing  as 
monoclinic  colorless  prisms  of  alkaline  reaction  (turning  red  litmus 
blue;  in  regard  to  the  reaction  of  borax  with  turmeric  see  p.  185). 
Borax  is  soluble  in  17  parts  water,  and  on  heating  borax  it  loses  its 
water  of  crystallization  and  yields  vitreous,  fused  borax,  NajB^O,; 


SODIUM.  213 

which  is  used  in  blowpipe  analysis,  as  it  gives  characteristic  colors 
with  many  metallic  oxides. 

Sodium  Carbonate,  NaaCOg,  Soda.  Occurrence.  Dissolved  in 
certain  lakes  in  Asia,  Africa,  North  America,  and  in  certain  mineral 
waters  (Carlsbad,  Vichy).  It  occurs  as  an  efflorescence  on  the  soil 
in  Egypt,  Hungary,  and  South  America.  It  is  contained  to  a  great 
extent  in  the  ashes  of  certain  sea-plants  (especially  in  the  varieties 
of  Salsola  and  Salicornia),  as  well  as  from  seaweeds,  from  which  it 
was  formerly  prepared  in  the  same  manner  as  potassium  carbonate 
from  the  ashes  of  land-plants. 

Preparation.  1.  Leblanc's  Method  (1794).  Common  salt  is 
heated  with  sulphuric  acid  (or  SO2,  air,  and  steam  are  passed  over  NaCl, 
p.  211),  when  sodium  sulphate  and  hydrochloric  acid  are  produced. 
This  last  is  allowed  to  pass  off  and  is  absorbed  by  water. 

The  sodium  sulphate  is  fused  at  a  red  heat  with  chalk  (CaCOg) 
and  hard  coal,  when  the  sodium  sulphate  is  first  reduced  by  the  carbon 
into  sodium  sulphide:  Na2S04+2C  =  Na2S+2C02.  The  sodium 
sulphide  is  then  transformed  by  the  calcium  carbonate  into  sodium 
carbonate  and  calcium  sulphide:    Na2S+CaC03=Na2C03+CaS. 

The  black-  mass  thus  obtained,  called  black  ash,  contains  30-45 
per  cent,  sodium  carbonate,  30  per  cent,  calcium  sulphide,  besides 
lime  (CaO),  undecomposed  calcium  carbonate,  coal,  and  sand.  It 
is  lixiviated  with  cold  water,  which  dissolves  the  sodium  carbonate. 

The  soda  solution  (lye)  is  evaporated,  while  a  continuous  flow 
of  new  lye  is  added,  until  sodium  carbonate,  as  Na2C03+  H2O,  separates 
out,  and  this  removed  as  soon  as  formed.  These  crystals  are  heated 
to  remove  water  and  any  organic  matter  mixed  with  them,  and  occurs 
in  commerce  as  calcined  soda,  or  the  crystals  are  recrystallized  from 
watery  solution  and  obtained  as  NajCOg+lOHjO  (p.  214). 

For  every  kilogram  of  soda  there  remains  from  1  to  1^  kilograms 
of  residue,  which  contains  all  the  sulphur  derived  from  the  sulphuric 
acid  used.  This  residue  by  the  action  of  the  air  develops  sulphuretted 
hydrogen,  while  the  polysulphides  produced  dissolve  when  exposed  to 
rain,  so  that  the  air  and  water  in  the  neighborhood  of  a  Leblanc  soda 
factory  are  contaminated  to  a  considerable  extent.  In  more  recent  times 
the  fresh  residue  is  treated  with  carbon  dioxide,  CaS  +  H^0  +  C02= 
CaCOg+HgS;  the  sulphuretted  hydrogen  is  either  burnt  with  a  dimin- 
ished supply  of  air,  when  most  of  the  sulphur  separates  out  (p.  122),  or 
it  is  completely  burnt  into  sulphur  dioxide,  which  is  used  again  in  the 
preparation  of  sulphuric  acid  (Chance-Claus  method  of  regenerating 
sulphur). 


214  INORGANIC  CHEMISTRY. 

2.  Solvay  or  Ammonia  Method  (1863).  A  solution  of  ammonium 
bicarbonate  reacts  with  a  solution  of  sodium  chloride,  forming  ammo- 
nium chloride  and  sodium  bicarbonate,  which  is  less  soluble  and  sepa- 
rates out :  NaCl+  NH^.HCOs  =  NH,C1+  NaHCO,. 

Sodium  bicarbonate  yields  calcined  soda  on  heating: 
2NaHC03  =  Na2C03+ 1{,0-\-  CO^. 

The  ammonia  is  reobtained  from  the  ammonium  chloride  by 
heating  with  lime  or  magnesia:   2NH4Cl+CaO  =  CaCl24-2NH3+HjO. 

On  passing  carbon  dioxide  and  ammonia  into  a  solution  of  salt 
the  process  described  above  takes  place  again: 

NaCl+ NH3+ CO2+ H^O  =  NaHC03+ NH.Cl. 

The  decomposition  takes  place  even  at  the  ordinary  temperature. 
In  practice  the  carbon  dioxide  is  passed  into  the  liquid  under  pressure 
not  below  40°.  The  residue  of  MgClg  or  CaClj  obtained  in  this  process 
is  used  in  the  preparation  of  chlorine  (p.  133). 

The  Solvay  process  requires  much  less  coal,  does  not  yield  any  residue 
which  contaminates  the  neighborhood,  and  yields  a  purer  soda  than  the 
Leblanc  method.  It  would  have  entirely  supplanted  this  last  method 
if  hydrochloric  acid,  obtained  by  this  process,  were  not  an  important  by- 
product. 

3.  Electrolytic  Process.  Sodium  chloride  solutions  are  decom- 
posed by  the  electric  current,  when  chlorine  appears  at  the  carbon 
positive  pole  and  sodium  at  the  iron  negative  pole.  This  sodium 
forms  NaOH  with  the  water,  and  this  is  then  transformed  into  the 
difficultly  soluble  NaHCOg  (see  2)  by  passing  COj  into  the  solution, 
which  yields  calcined  soda  on  heating  (see  below). 

4.  For  preparation  of  soda  from  cryolite  see  Aluminium  Hydroxide, 
p.  250. 

Properties.  Anhydrous  or  calcined  soda  forms  a  white  mass 
or  a  white  powder  which  melts  at  a  red  heat  and  has  an  alkaline 
reaction.  If  a  not  too  concentrated,  hot,  aqueous  solution  is  allowed 
to  cool  in  the  air,  large  colorless  monoclinic  prisms,  Na2CO3+10H2O, 
sodium  carbonate  (crude  washing  soda) ,  separate  out.  By  repeated 
recrystallization  purified  soda  is  obtained,  NajCOg+lOHjO.  Crys- 
talline soda  quickly  loses  a  part  of  its  water  of  crystallization  in  the 
air  and  changes  into  a  white  powder:  Na2C03+2H20,  sodium  car- 
bonate (siccum). 

100  parts  water  at  15°  dissolve  55  parts  soda,  at  38°  138  parts,  at 
100°  100  parts.  Hence  on  heating  a  solution  saturated  at  38°  soda 
separates  out  and  precipitates  at  50°  Na-COa+THoO,  at  100°  Na,COo+ 
HaO,  and  below  38°  NajCOa+lOH.O. 


CESIUM.— RUBIDIUM.— LITHIUM.  215 

Sodium  bicarbonate,  NaHCOg,  primary  or  acid  sodium  carbonate, 
Bodium  hydrocarbonate  (baking  soda) ,  separates  out  on  passing  carbon 
dioxide  into  a  concentrated  solution  of  sodium  carbonate:  Na^C03+ 
H20+C02  =  2NaHC03.  The  cheaper  varieties  are  prepared  accord- 
ing to  the  Solvay  process  (p.  214)  as  an  intermediary  product.  It  forms 
crystalHne  crusts  or  a  white  crystaUine  powder  having  a  faint  alka- 
line reaction  and  soluble  in  12  parts  cold  water.  The  moist  powder 
or  the  powder  exposed  to  moist  air  loses  carbon  dioxide. 

Sodium  silicate  is  prepared  in  a  manner  similar  to  that  of  potassium 
silicate  (p.  208).     Its  watery  solution  is  called  "water-glass." 

b.  Detection  of  Sodium  Compounds. 

1.  They  color  a  non-luminous  flame  intensely  yellow.  The  spec- 
trum of  this  flame  shows  a  single  bright-yellow  line. 

2.  All  sodium  salts  are  soluble  in  water  with  the  exception  of 
disodium  pyroantimonate  (Na2H2Sb207),  which  is  obtained  as  a  white 
granular  precipitate  when  a  solution  of  a  sodium  compound  is  treated 
with  a  solution  of  dipotassium  pyroantimonate. 

3.  Csesium.  4.  Rubidium. 

Atomic  weight  132.9  =Cs.  Atomic  weight  85.4  =  Rb. 

Both  of  these  elements  occur  only  in  combination,  rather  widely 
distributed,  always  together,  but  always  in  small  amounts;  thus  in  many 
plant-ashes,  in  several  minerals,  such  as  lepidolite,  pollucite,  triphylite, 
and  many  mineral  springs,  especially  of  Nauheim  and  Diirkheim,  also 
in  the  mother-liquors  of  carnallite.  They  give  characteristic  spectral 
lines  and  hence  their  names. 

They  are  both  obtained  by  the  electrolysis  of  their  chlorides,  and 
inflame  spontaneously  in  the  air  when  in  large  pieces,  hence  must  be 
kept  under  petroleum.  Caesium  has  a  specific  gravity  of  1.84,  is  soft, 
silvery  in  appearance,  melts  at  26.4°,  boils  at  270°,  and  the  metal  as  well 
as  its  compounds  gives  a  violet  color  to  a  non-luminous  flame.  The 
spectrum  of  this  flame  show  two  intense  blue  lines. 

Rubidium,  sp.  gr.  1.52,  is  soft,  silvery  in  appearance,  melts  at  38.5, 
boils  at  about  500°,  and  the  metal  and  its  compounds  give  a  violet  color 
to  a  non-luminous  flame.  The  spectrum  of  this  flame  shows  two  dark 
red  and  two  violet  lines. 

5.  Lithium, 

Atomic  weight  7.03=  Li, 

occurs  only  combined,  very  widely  distributed,  but  always  in  very  small 
quantities,  as  in  many  mineral  waters  (Baden-Baden,  Carlsbad,  Marien- 
bad),  and  in  the  ashes  of  many  plants,  especially  in  tobacco  and  the  common 
beet.  Certain  minerals,  such  as  triphylite,  lepidolite,  petalite,  amblygo- 
nite,  contain  as  much  as  4.5  per  cent,  lithium.     It  is  obtained  by  the  elec- 


216  INORGANIC  CHEMISTRY. 

trolysis  of  the  chloride  as  a  silver-white  metal  which  melts  at  186°  and 
which  boils  above  800°.  The  metal  has  a  specific  gravity  of  0.59  and 
hence  is  the  lightest  of  all  metals  In  other  regards  it  behaves  like  sodium. 
It  forms  the  connecting  Unk  between  the  alkali  metals  and  the  alkaline 
earths,  as  its  carbonate  and  phosphate  are  difficultly  soluble  in  water. 
Lithium  and  its  compounds  give  a  beautiful  red  color  to  the  non-lumi- 
nous flame,  and  the  spectrum  of  this  flame  gives  one  red  line. 

Lithium  carbonate,  LigCOg,  is  obtained  as  a  white  crystalline  precipi- 
tate by  treating  a  concentrated  solution  of  LiCla  with  ammonium  car- 
bonate. It  is  soluble  in  80  parts  water,  giving  an  alkaline  reaction  to 
the  solution. 

6.  Ammonium. 

Ammonia  combines  directly  with  all  acids,  forming  salts  which  on 
account  of  their  similarity  to  the  potassium  compounds  will  be  treated 
of  at  this  place.  The  hydrogen  of  the  acid  is  replaced  by  the 
monovalent  radical  ammonium  NH4,  which  does  not  exist  free. 
All  ammonium  salts  are  isomorphous  with  the  analogous  potassium 
salts. 

The  metallic  character  of  the  NH4  group  is  shown  by  the  existence 
of  ammonium  amalgam,  which  has  the  same  character  as  potassium 
amalgam.  The  ammonium  amalgam  is  obtained  as  a  voluminous 
metallic  mass  when  sodium  amalgam  is  treated  with  a  solution 
of  ammonium  chloride:  (Hg.Na)  +  NH4Cl  =  (Hg.NH4)  +  NaCL  It 
quickly  decomposes  into  hydrogen,  mercury,  and  ammonia. 

a.  Compounds  of  Ammonium. 

Ammonium  oxide  (NH4)20,  and  ammonium  hydroxide,  (NH4)0H, 
have  not  been  isolated  (see  Ammonia). 

Ammonium  peroxide,  (NH4)202,  separates  on  mixing  solutions  of 
2NH3  and  H2O2  cooled  to  —20°,  and  forms  colorless  cubes  which  decom- 
pose at  ordinary  temperatures  into  2NH3  +  H2O  +  O. 

Ammonium  sulphide,  (NH4)2S,  separates  as  colorless  crystals  on  bringing 
1  vol.  H2S  gas  and  2  vols.  NH3  together  at  -20°. 

Ammonium  hydrosulphide,  ammonium  sulphydrate,  (NHJSH, 
forms  colorless  crystals  on  cooling  equal  volumes  of  NH3  and  HjS  gas 
to  0°.  This  body  is  obtained  in  solution  by  saturating  a  solution  of 
ammonia  with  sulphuretted  hydrogen:  NH3+H_,S  =  NH4SH.  It 
forms  a  colorless  solution  which  becomes  yellow  in  the  air,  whereby 
ammonium  polysulphide  and  water  are  produced  (ammonium  sulphide 
used  in  the  laboratory). 

Ammonium  chloride,  sal  ammoniac,  NH4CI,  occurs  in  volcanic 
and  coal  deposits,  is  obtained  by  neutralizing  the  ammoniacal  liquor 
of  the  gas-works  (p.  148)  with  hydrochloric  acid,  evaporating  the 


AMMONIUM.  217 

solution  to  dryness  and  subliming  the  residue,  or  by  the  sublimation 
of  sodium  chloride  with  ammonium  sulphate: 

2NaCl+  (NH  J,SO,  =  2NH,C1+  Na^SO^. 

When  subhmed  it  forms  fibrous  crystalline  masses,  and  when 
crystallized  from  water  it  forms  a  crystalline  powder.  It  is  colorless 
and  odorless,  volatile  on  heating,  without  melting,  dissolves  in  4 
parts  water,  and  is  nearly  insoluble  in  alcohol. 

Ammonium  bromidei  NH4Br,  is  obtained  on  the  sublimation  of 
potassium  bromide  with  ammonium  sulphate,  and  forms  white  cubes 
or  a  white  crystalline  powder  which  is  readily  soluble  in  water  and 
difficultly  soluble  in  alcohol. 

Ammonium  iodide,  NH^I,  is  prepared  from  potassium  iodide  and 
ammonium  sulphate  and  forms  white  deliquescent  cubes  which  are  readily 
soluble  in  alcohol.     It  splits  off  iodine  in  moist  air. 

Ammonium  sulphate,  (NH4)2S04,  occurs  as  the  mineral  mascagnine. 
It  is  obtained  by  saturating  the  ammoniacal  liquor  of  the  gas-works 
with  sulphuric  acid  and  forms  colorless  and  odorless  crystals  which 
decompose  at  high  temperatures.     It  is  used  as  a  valuable  fertilizer. 

Ammonium  persulphate,  (NHJaSgOg,  forms  colorless  prisms  which 
are  readily  soluble.  It  is  prepared  on  a  large  scale  being  used  as  an 
oxidizing  agent  (p.  131)  and  is  also  used  in  photography. 

Ammonium  nitrate,  (NH4)N03,  produced  by  saturating  a  solution 
of  ammonia  with  nitric  acid  and  evaporating  this  product.  It  forms 
colorless  crystals  which  are  soluble  in  water  and  which  decompose  into 
water  and  nitrous  oxide  (p.  155)  when  heated.  It  is  used  as  an  explosive 
when  mixed  with  saltpeter  and  resins. 

Ammonium  nitrite,  (NHJNOj.  In  regard  to  formation  and  occur- 
rence see  Nitrous  Acid.  It  is  obtained  by  mixing  a  solution  of  silver 
nitrite  with  an  ammonium  chloride  solution,  filtering  off  the  silver  chloride, 
and  carefully  evaporating  the  filtrate.  It  forms  colorless  crystalline 
masses  which  on  heating  yield  water  and  nitrogen  (p.  146). 

Ammonium  phosphates.  Tertiary  ammonium  phosphate  (NH4)3P04, 
secondary  ammonium  phosphate,  (NH4)2HP04,  and  primary  ammonium 
phosphate,  (NH4)H2P04,  are  obtained  in  a  manner  similar  to  that  of  the 
corresponding  sodium  phosphates.  On  careful  heating  they  leave  a 
residue  of  metaphosphoric  acid  thus: 

(NH4)H2P04=  HPO3+H2O +NH3. 

Sodium-ammonium  phosphate,  Na(NH4)HP04  +  4H20  (microcosmic 
salt),  occurs  in  guano  and  stale  urine  (hence  formerly  called  Sal  urinae 
fixum).  If  5  parts  disodium  phosphate  and  2  parts  diammonium  phosphate 
are  dissolved  in  hot  water  and  allowed  to  cool,  colorless  prisms  separate 
out: 

Na^HPO,  +  (NH4)2HP04=^  2Na(NH4)HPO,. 


218  INORGANIC  CHEMISTRY. 

'  It  is  used  in  blowpipe  analysis,  as  on  heating  it  is  converted  intc 
sodium  metaphosphate,  which  dissolves  many  metallic  compounds  with 
the  production  of  characteristic  colors: 

Na(NH4)HPO,=  NaP03+H20  +  NH3. 

Ammonium  carbonate,  (NH4)2C03  +  H20,  precipitates  when  ammonia 
is  passed  into  a  concentrated  solution  of  commercial  ammonium  carbonate 
(see  below).     On  allowing  to  lie  in  the  air  it  is  converted  into 

Ammonium  bicarbonate,  (NH4)HC03,  which  precipitates  on  saturat- 
ing an  ammonia  solution  with  carbon  dioxide.  Both  of  these  bodies 
form  colorless  crystals  which  decompose  at  60°  into  carbon  dioxide  and 
ammonia. 

Commercial  ammonium  carbonate  is  a  combination  of  primary  ammo- 
nium carbonate  with  ammonium  carbamate  (which  see) : 

HO-CO-0(NH)4  +  H2N-CO-0-(NH,). 

It  is  produced  in  the  decay  of  many  organic  nitrogenous  bodies  and 
was  formerly  obtained  by  the' dry  distillation  of  such  bodies,  e.g.,  horn, 
hoofs,  claws,  bones,  and  leather  refuse,  etc. 

It  was  then  strongly  contaminated  with  inflammable  oils  and  was 
called  in  pharmacy  Sal  cornu  cervi  volatile,  Hartshorn  salt,  ammonium 
carbonicum  pyroleosum.  It  is  now  obtained  by  subliming  calcium 
carbonate  (chalk)  with  ammonium  sulphate  or  ammonium  chloride. 
It  forms  white,  fibrous,  crystalline  masses  which  are  soluble  in  5  parts 
water.  On  exposure  to  the  air  it  develops  NHg  and  COg  and  is  trans- 
fonned  into  ammonium  bicarbonate  which  is  less  soluble. 

h.  Detection  of  Ammonium  Compounds. 

1.  The  hydroxides  of  the  alkaU  metals  and  the  alkaline  earthy 
metals  set  ammonia  free  from  ammonium  compounds,  which  can  be 
readily  detected  by  the  odor  as  well  as  by  turning  turmeric  paper 
brown  (p.  150). 

2.  Platinum  chloride  and  also  tartaric  acid  produce  precipitates  in 
ammonium  salt  solutions  analogous  in  composition  to  the  potassium 
compounds,  namely,  ammonium-platinum  chloride,  (NHJaPtClg,  and 
ammonium  bi tartrate,  C4H5(NH4)08. 

3.  All  ammonium  salts  are  volatile  on  heating. 

4.  In  solution  traces  of  ammonium  salts  produce  a  brown  colora- 
tion or  precipitate  with  Nessler's  reagent  (see  Mercuric  Iodide). 

GROUP  OF  ALKALINE-EARTH  METALS. 
Calcium.     Strontium.     Bariimi. 

These  are  divalent  metals,  which  combine  at  ordinary  temperatures 
with  oxygen  and  also  decompose  water,  forming  strong  basic  oxides  (the 
alkaline  earths)  and  hydroxides  which  are  less  soluble  in  water  than 
the  alkalies.  The  oxides  are  not  reduced  into  the  metals  by  carbon  nor 
by  hydrogen.     Their  normal  phosphates,  sulphates,  and  carbonates  are 


CALCIUM.  219 

soluble  with  very  great  difficulty  in  water,  or  are  insoluble  therein,  while 
their  sulphides,  like  those  of  the  alkaUes,  are  readily  soluble.  The  solu- 
bility of  the  hydroxides  increases  from  calcium  to  barium,  and  the  solu- 
biUty  of  the  sulphate  diminishes  from  calcium  to  barium. 

They  are  called  alkaline-earth  metals  because  they  have  properties 
similar  to  the  alkali  metals  as  well  as  to  the  earthy  metals. 

Their  specific  gravity,  their  melting-point,  their  volatility  and  chemi- 
cal energy  increase  with  their  atomic  weight.  Thus  calcium  hydroxide 
and  carbonate  are  readily  decomposed  on  heating,  while  barium  hydroxide 
is  not  at  all  decomposed,  and  barium  carbonate  only  with  difficulty, 
and  the  corresponding  strontium  compounds  are  intermediate  in  their 
behavior,    » 

Their  salts  are  not  decomposed  by  ammonia  solution,  in  contradis- 
tinction to  the  salts  of  the  groups  which  follow. 

With  hydrogen  they  form  hydrides,  CaHj,  SrHg,  BaHg,  which  are 
colorless  solids. 

These  metals  combine  with  nitrogen  at  a  red  heat,  forming  nitrides, 
CagNg,  SrgNg,  BagNg,  which  with  water  suffer  the  following  decomposition: 

Ca3N2  +  6HOH=3Ca(OH)2  +  2NH3. 

With  the  heat  of  the  electtic  furnace  they  combine  with  carbon,  form- 
ing carbides,  CaCg,  SrCg,  BaCg,  which  is  the  reason  that  the  alkaline-earth 
metals  are  not  obtained  on  heating  their  oxides  with  carbon  as  the  metal 
which  is  set  free  immediately  combines  with  the  carbon. 

I.  Calcium. 

Atomic  weight  =  40.1  =Ca. 

Occurrence.  Never  free,  but  its  compounds  are  found  extensively, 
often  in  large  quantities.  Calcium  carbonate  and  calcium  sulphate 
(which  see)  occur  as  very  large  deposits  and  form  the  chief  constituents 
of  the  solids  of  spring-  and  river- waters.  Calcium  silicate  is  a  constitu- 
ent of  nearly  all  siliceous  minerals,  and  calcium  phosphate  occurs  in 
apatite  and  phosphorite  (p.  162).  Calcium  salts  always  occur  in  the 
plant  and  animal  organisms. 

Preparation  and  Properties.  Calcium  is  obtained  by  the  elec- 
trolysis of  fused  calcium  chloride  or  by  heating  calcium  iodide  with 
sodium.  It  is  a  silvery-white  soft  metal,  harder  than  lead  and  having 
a  specific  gravity  of  1.58  and  melting  at  760°,  but,  as  it  slowly  oxi- 
dizes in  dry  air,  it  must  like  potassium  be  kept  beneath  petroleum. 

a.  Compounds  of  Calcium. 
Calcium  oxide,  CaO,  caustic  lime,  lime,  burnt  lime,  is  obtained 
by  heating  to  a  red  heat  pure  calcium  carbonate  (white  marble)  i 
but  on  a  larger  scale  by  heating  impure  calcium  carbonate  (the  lime- 
stones) in  so-called  limekilns.  It  forms  hard,  white,  amorphous, 
alkaline  masses  which  become  crystalline  at  2500°  and  fusible  at 


220  INORGANIC  CHEMISTRY. 

about  3000°,  absorb  moisture  and  carbon  dioxide  from  the  air,  and 
are  transformed  into  CaCOg  and  Ca(0H)2.  On  account  of  its  high 
refractory  power  calcium  oxide  is  used  in  the  construction  of  crucibles 
for  the  oxyhydrogen  blowpipe,  as  well  as  for  the  Drummond  hme- 
hght  (p.  113).  It  combines  wdth  water  with  the  evolution  of  great 
heat  (slaking  of  lime),  producing 

Calcium  hydroxide,  Ca(0H)2,  slaked  lime,  which  is  a  white 
porous  powder  that  forms  a  pasty  mass  with  little  water,  and  with 
more  water  the  so-called  milk  of  Hme.  It  is  soluble  in  700  parts  cold 
water  and  in  1300  parts  hot  water;  hence  a  cold  saturated  solution 
becomes  cloudy  on  heating. 

The  saturated  watery  solution,  called  hme-water,  aqua  calcis, 
becomes  turbid  when  exposed  to  the  air  because  of  the  formation 
and  precipitation  of  calcium  carbonate. 

Mortar.  Calcium  hydroxide  forms  calcium  carbonate  with  the  carbon 
dioxide  of  the  air  and  gradually  becomes  crystalline  and  hence  solid; 
and  upon  this  fact  depends  the  hardening  of  air-mortar,  which  is  a  pasty 
mixture  of  sand,  slaked  lime,  and  water.  The  equation  Ca(OH)2+C02= 
CaCOg+HgO  explains  the  great  abundance  of  moisture  in  newly  con- 
structed buildings. 

Cement.  If  a  limestone  contains  considerable  aluminium  silicate 
(clay),  then  calcium  silicate  is  formed  on  burning  the  same.  This  cal- 
cium silicate  cannot  be  further  slaked  with  water,  i.e.,  calcium  hydroxide 
cannot  be  produced.  Nevertheless  such  a  product  hardens  when  mixed 
with  water  and  remains  hard  even  under  the  surface  of  water;  hence  it 
is  called  hydraulic  lime  or  cement,  and  is  used  especially  for  hydraulic 
use.  The  pasty  mixture  of  sand,  cement,  and  water  is  called  water- 
mortar.  The  hardening  is  caused  by  the  formation  of  hydrated  aluminium- 
calcium  silicates  and  basic  calcium  aluminate  (see  Aluminium). 

Calcium  sulphide,  CaS,  is  obtained  pure  in  the  same  manner  as  KgS, 
and  impure  from  the  residues  in  soda  manufacture.  It  is  insoluble  in 
cold  water,  but  is  slowly  decomposed  by  it  into  difficultly  soluble  calcium 
hydroxide  and  readily  soluble  calcium  hydrosulphide: 

2CaS  +  2H20=  Ca(OH)2  +  Ca(SH)2. 

Pure  calcium,  strontium,  and  barium  sulphides  shine  in  the  dark  after 
exposure  to  sunlight,  but  lose  this  property  in  moist  air  (Bolognian  stone, 
used  as  a  phosphorescent  paint). 

Calcium  hydrosulphide,  calcium  sulphydrate,  Ca(SH)2,  is  produced  in 
purifying  illuminating-gas  (fj;as-lime),  and  is  obtained  as  a  gray  mass  by 
the  action  of  R^  "PO"  Ca(0H)2;  thus,  Ca(OH)2  +  2H2S=Ca(SH)2  +  2H20. 
It  may  also  be  prepared  from  calcium  sulphide  (see  above).  Its  watery 
paste  destroys  hair  (Bottger's  depilatory,  rhusma)  and  is  used  to  remove 
wool  from  sheep's  hides.  On  boiling  with  water  it  decomposes:  CaCSH), 
=CaS  +  H2S.  ' 

Calcium  poly  sulphides,  CaSg,  CaS.,,  CaSg,  etc.,  are  obtained  mixed 
with  calcium  sulphate  on  heating  calcium  oxide  with  the  corresponding 


CALCIUM.  221 

amounts  of  sulphur.  They  behave  hke  the  corresponding  potassium 
polysulphides  and  are  used  in  the  preparation  of  precipitated  sulphur 
(milk  of  sulphur)  and  HgSj. 

Calcium  chloride,  CaClj,  occurs  in  tachhydrite,  CaCl2+MgCl^+ 
I2H2O,  and  is  obtained  by  dissolving  calcium  carbonate  (marble, 
chalk)  in  hydrochloric  acid  and  is  also  procured  in  large  quantities  in 
the  manufacture  of  ammonia  as  well  as  in  the  Solvay  soda  process. 
It  is  obtained  from  its  solutions  by  evaporation  as  colorless  crystals, 
CaCl2+6H20,  which  dissolve  in  water  with  great  lowering  of  tem- 
perature. The  crystals  melt  at  29°  in  their  water  of  crystaUization, 
and  at  20G°  white  porous  anhydrous  CaCl2  is  obtained.  This  dissolves 
in  water  with  generation  of  heat  and  melts  at  719°,  forming  a  crystalline 
mass  which  absorbs  water  with  activity  and  deliquesces  in  the  air, 
and  hence  is  used  as  a  drying  agent.  It  also  absorbs  ammonia  and 
forms  a  white  powder  therewith :  CaCl2+  8NH5.  The  large  quantities 
of  calcium  chloride  obtained  as  a  by-product  in  technical  processes 
are  used  in  the  preparation  of  chlorine  (which  see). 

Calcium  fluoride,  CaFg,  occurs  as  colorless,  yellow,  green,  or  violet 
crystals  or  masses  called  fluor-spar,  and  in  small  amounts  in  plant-ashes, 
bones,  and  the  enamel  of  the  teeth.  It  is  insoluble  in  water  and  phos- 
phoresces on  heating  or  when  exposed  to  the  sunlight.  On  account  of  its 
ready  fusibility  it  is  used  as  a  flux  in  metallurgical  processes. 

Calcium  hypochlorite,  Ca(0Cl)2,  is  obtained  as  thin  crystals  by  strongly 
cooling  a  concentrated  aqueous  solution  of  chloride  of  lime. 

Chloride  of  lime,  bleaching-powder,  consists  of  calcium  chloride 

OCl  OPl 

and  calcium  hypochlorite.  Ca<Q^  +  CaCl„  or  of  2Ca<p,    . 

Calcium  chloride  cannot  be  isolated  from  the  chloride  of  lime, 
hence  the  last  formula  is  probably  correct. 

Preparation.  Chlorine  is  passed  over  layers  of  dry  calcium  hy- 
droxide at  a  temperature  which  must  not  rise  above  25°,  so  that  no 
calcium  chlorate  is  produced: 

2Ca(OH)2+4a  =2Ca(OCl)a-h2H20. 

It  is  not  possible  to  have  all  the  calcium  hydroxide  combine  with 
chlorine,  so  that  the  product  only  contains  25  and  30  per  cent,  availa- 
ble chlorine  (p.  222)  and  always  contains  calcium  hydroxide. 

Properties.  White  powder  having  a  chlorine-hke  odor.  The 
calcium  chloride  and  hypochlorite  dissolve  in  water,  while  the  calcium 
hydroxide  remains  in  great  part  undissolved.     The  watery  solutions 


222  INORGANIC  CHEMISTRY. 

have  a  bleaching  action.  Hydrochloric  acid  and  sulphuric  acid 
evolve  chlorine  from  chloride  of  lime,  hence  it  serves  in  the  prepara- 
tion of  chlorine  for  the  destruction  of  organic  pigments,  disagreeable 
odors,  and  for  disinfection.  Chloride  of  lime  should  contain  at  least 
25  per  cent,  of  active  chlorine.  By  active  chlorine  we  mean  the 
quantity  of  chlorine  set  free  on  adding  the  above-mentioned  acids  to 
chloride  of  lime.  It  amounts  to  double  the  quantity  contained  in 
the  calcium  hypochlorite: 

CaCl(0Cl)  +  2HCl  =CaCl2  +H2O+2CI; 
CaCl(OCl)  +  H2SO4  =  CaS04+  Bfi-{-  2C1. 

Chloride  of  lime  evolves  hypochlorous  acid  on  standing  in  the  air, 
being  set  free  by  the  action  of  the  carbon  dioxide  of  the  air.  On  heating 
or  in  sunlight  it  slowly  decomposes  into  CaClg  +  Oj,  and  the  generation 
of  oxygen  may  take  place  with  explosive  violence;  hence  chloride  of  lime 
must  be  kept  cool  and  dark  and  not  in  completely  closed  vessels. 

Many  metallic  oxides,  such  as  CogOg,  CuO,  develop  oxygen  from  chlo- 
ride of  lime  on  warming.  Probably  a  part  of  the  oxygen  of  the  metal 
combines  with  the  chloride  of  lime,  setting  free  oxygen:  CaCl(OCl)  + 
2Co203=CaCl2  +  2CoO  +  20.  The  lower  metallic  oxide  formed  is  then 
again  transformed  by  the  chloride  of  lime  into  the  higher  metallic  oxide, 
which  in  turn  acts  upon  the  chloride  of  lime. 

Ammonia  when  heated  with  chloride  of  lime  generates  nitrogen  (p.  147). 

Nitric  acid  sets  hypochlorous  acid  free  (p.  137). 

Hydrogen  peroxide  develops  oxygen  (p.   119). 

Calcium  Sulphate,  CaS04.  Occurrence.  1.  Inmost  spring-waters 
(permanently  hard  waters,  p.  116). 

2.  As  anhydrite  in  anhydrous  rhombic  crystals. 

3.  As  gypsum,  CaS04-|-2H20,  it  forms  dense  masses;  as  crys- 
talline masses  it  is  called  alabaster,  and  as  monoclinic  prisms  it 
forms  selenite,  etc. 

Preparation.  By  treating  a  concentrated  solution  of  a  calcium 
salt  with  concentrated  sulphuric  acid  a  white  crystaUine  precipitate 
of  calcium  sulphate,  CaS04+2H20,  is  obtained. 

Properties.  It  is  soluble  in  400  parts  water  and  loses  IJ  mole- 
cules of  its  water  of  crystallization  on  being  heated  to  120°;  the 
product,  2CaS04+H20,  is  called  burnt  gypsum  or  plaster  of  Paris. 
If  this  is  mixed  into  a  paste  with  water,  it  unites  with  this  with  the 
development  of  heat  and  quickly  hardens.  The  use  of  plaster  of 
Pans  in  the  preparation  of  casts,  moulds,  plaster  bandages,  etc., 
is  dependent  upon  this  property.  If  gypsum  is  heated  to  160°,  it 
loses   all  its  water  of  crystallization  and  no  longer  combines  with 


CALCIUM.  223 

water,  being  then  called  dead  burnt  plaster.     Anhydrite  does  not 
combine  with  water. 

Tertiary  or  Tricalcium  phosphate,  Ca3(P04)2  (also  neutral  cal- 
cium phosphate),  occurs  as  apatite  and  phosphorite  (p.  162)  and  con- 
stitutes two-thirds  of  the  bones  of  animals;  it  forms  the  chief  mass 
of  the  coprohtes,  phosphorites,  osteolites,  and  certain  varieties  of 
guano,  and  is  found  in  the  ash  of  all  animal  and  plant  organs.  It  is 
insoluble  in  pure  water  but,  on  the  contrary,  is  partly  soluble  in  water 
containing  CO^  or  certain  salts. 

A  basic  calcium  phosphate,  Ca3(P04)2+CaO,  is  the  chief  constituent 
of  the  Thomas  slag  obtained  in  the  dephosphorization  of  iron  and  which 
is  an  excellent  fertilizer.  Its  value  is  dependent  upon  the  fact  that  it 
does  not  have  to  be  converted  into  soluble  superphosphate  like  the 
other  calcium  phosphate,  but  is  ground  finely  (Thomas  phosphate),  and 
is  readily  decomposed  by  the  carbonic  acid  and  moisture  of  the  soil. 

Pure  calcium  phosphate  is  obtained  by  mixing  a  solution  of  disodium 
phosphate  treated  with  ammonia  with  a  solution  of  calcium  chloride. 
This  precipitate  is  gelatinous  and  when  dry  forms  a  white,  amorphous, 
odorless  and  tasteless  mass. 

Secondary  calcium  phosphate,  CaHP04  +  2H20  (dicalcium  phosphate), 
occurs  often  in  urinary  calculi  and  sediments  as  microscopic  crystals.  It 
is  obtained  as  a  white  crystalline  powder  insoluble  in  water  by  mixing  a 
solution  of  disodium  phosphate  with  a  calcium  chloride  solution. 

Primary  calcium  phosphate,  CaH^(P0j2  (monocalcium  phosphate),  is 
obtained  by  treating  tertiary  or  secondary  calcium  phosphate  with  sul- 
phuric acid  (p.  162,  a),  and  separates  out  on  the  evaporation  of  the  solution 
as  colorless,  deliquescent,  acid-reacting  scales.  It  is  readily  soluble  in 
water  and  hence  is  better  suited  as  a  fertilizer  than  the  tertiary  salt. 
When  mixed  with  gypsum  it  forms  superphosphate,  which  is  used  as 
a  fertilizer. 

Calciimi  carbide,  CaCg,  is  obtained  by  heating  CaO  with  carbon  in  the 
electric  furnace.  When  pure  it  forms  gold-like  crystals,  and  in  com- 
merce it  forms  grayish-black  masses  which  with  water  and  acids  gener- 
ate acetylene  gas,  C2H2  (which  see). 

Calcium  Carbonate,  CaCOj.  Occurrence.  1.  Amorphous  or  not 
markedly  crystalline  as  limestone;  in  crystalline  granules  as  marble; 
in  amorphous  or  crystalline  granules  combined  with  magnesium  car- 
bonate as  dolomite,  CaCOg+MgCOg;  amorphous  as  chalk;  schistous- 
like  as  lithographic  stone,  etc. 

2.  As  calc-spar  (calcite)  in  hexagonal  crystals  (rhombohedrons), 
and  as  aragonite  in  rhombic  columns. 

3.  In  all  plant-ashes  and  in  all  animals,  especially  in  the  bones; 
in  the  urine  of  herbivorous  animals,  and  in  many  pathological  concre- 
tions, as  in  urinary  calculi,  etc.  It  forms  the  chief  constituent  of 
the  corals,  oyster-,  mussel-,  snail-,  and  egg-shells,  and  pearls. 


224  INORGANIC  CHEMISTRY. 

4.  It  also  occurs  in  fertile  soil  and  in  most  natural  waters. 

Preparation.  By  mixing  a  solution  of  a  calcium  salt  with  alkali 
carbonate  as  a  white  crystalline  precipitate  (precipitated  chalk). 

Properties.  On  heating  to  white  heat  it  decomposes  into  carbon 
dioxide  and  calcium  oxide:  CaC03  =  CaO+C02.  It  is  insoluble  in 
pure  water,  but  it  gradually  dissolves  in  the  presence  of  CO2,  forming 
the  primary  carbonate:  CaC03+H20+C02  =  CaH2 (003)2;  hence 
all  waters  coming  from  lime  soil  contain  primary  calcium  carbonate 
(temporary  hardness  of  water,  p.  116).  On  allowing  such  water  to 
stand  in  the  air  it  loses  COj  and  calcium  carbonate  precipitates,  and 
this  accounts  for  the  formation  of  thermal  tuff,  stalactites,  lime-tuff, 
etc.  The  same  change  takes  place  on  boiling,  when  the  calcium  car- 
bonate separates  as  a  crystalUne  crust  on  the  vessel  and  forms  the 
boiler  incrustations  or  scales. 

Calcium  silicate,  CaSiOg,  is  a  constituent  of  many  sihceous  min- 
erals and  is  found  pure  in  crystaUine  masses  as  woUastonite.  It 
is  obtained  as  a  white  crystalline  mass  by  fusing  silicon  dioxide 
(sand)  with  calcium  carbonate. 

Gla^s.  Calcium  silicate  is  opaque  and  insoluble  in  water;  alkali 
silicates  are  transparent  and  soluble  in  water.  The  calcium  as  well 
as  the  alkali  silicates  are  decomposable  by  acids.  If,  on  the  con- 
trary, calcium  silicate  is  fused  with  the  proper  proportion  of  alkali 
silicate,  we  obtain  a  transparent  amorphous  compound  which  is 
neither  attacked  by  water  nor  by  acids  and  is  called  glass.  In  the 
preparation  of  common  glass  there  is  fused  together  a  mixture  of  sand, 
limestone,  and  soda.  Bohemian  glass  is  made  with  potash  instead  of 
with  soda;  the  constituents  of  flint  glass  are  sand,  potash,  and  lead  oxide. 

1.  Common  white  glass  is  sodium-calcium  silicate  and  is  used  in 
the  preparation  of  drinking  glasses,  window  glass,  etc. 

2.  Crude  green  glass,  or  bottle  glass,  is  sodium-calcium  silicate,  which 
is  made  from  impure  material  in  which  the  ferrous  silicate  gives  a  green 
color  to  the  glass  and  the  ferric  silicate  gives  a  yellow  color. 

3.  Bohemian  glass,  crown  glass,  is  potassium-calcium  silicate;  it  is 
less  fusible  than  the  sodium  glass,  and  is  especially  used  in  the  prepara- 
tion of  chemical  utensils  which  must  withstand  high  temperatures. 

4.  English  crystal  glass,  flint  glass  or  paste,  is  potassmm-lead  silicate, 
which  fuses  readily,  is  highly  refractive,  takes  a  high  polish,  and  is  used 
for  optical  purposes  and  decorative  objects. 

5.  Jena  glass  is  characterized  by  its  refractive  and  dispersive  power 
and  hence  is  used  almost  exclusively  in  optical  apparatus.  It  is  pre- 
pared by  partly  replacing  the  silicates  by  boric  acid,  phosphoric  acid,  or 
fluorine  compounds. 


STRONTIUivI,  '  225 

6.  Colored  glass  is  obtained  by  dissolving  small  amounts  of  metallic 
oxides  in  the  fused  glass.  With  cobaltous  oxide  a  blue  glass  is  obtained, 
with  ferric  oxide  a  yellow,  with  cupric  or  chromic  oxide  an  emerald-green, 
with  uranium  oxide  a  fluorescent  greenish  yellow,  with  manganese 
oxide  a  violet,  with  sodium  sulphide  a  brown,  and  with  metallic  gold 
or  copper  a  ruby-red  glass.  Black  glass  is  simply  deeply  colored  violet, 
brown,  or  blue  glass.  Green  or  common  glass  (see  2)  is  decolorized 
on  the  addition  of  manganese  oxide  (brownstone)  or  didymium  salts 
or  traces  of  selenium,  as  the  violet  color  produced  is  complementary  to 
the  green.  Milk-glass  is  obtained  by  adding  bone-ash  or  stannic  oxide 
to  the  glass. 

h.  Detection  of  Calcium  Compounds. 

1.  They  color  the  non-luminous  flame  yellowish  red,  and  the 
spectrum  of  this  flame  shows  an  intense  green  and  a  violet  line. 

2.  Ammonium  oxalate  causes  a  white  precipitate  of  calcium 
oxalate  even  in  very  dilute  solutions  of  calcium  salts.  This  precipi- 
tate is  insoluble  in  acetic  acid  and  oxalic  acid.  Barium  and  stron- 
tium salts  are  only  precipitated  by  this  reagent  in  very  concentrated 
solutions. 

3.  Sulphuric  acid  precipitates  calcium  salts  only  from  concentrated 
solutions  and  not  from  dilute  solutions,  as  the  white  precipitate  of 
calcium  sulphate,  CaS04,  is  soluble  to  a  slight  extent  in  water. 

2.  Strontium. 

Atomic  weight  87.6=  Sr. 
Occurs  only  combined  and  then  as  strontianite,  SrCOs,  and  as 
colestine,  SrSOi.      The   yellow   metal   has  a  specific   gravity  of  2.5, 
melts  at   600°,  is  obtained  by  the  electrolysis  of   fused  strontium 
chloride,  and  is  similar  to  calcium  in  properties. 

a.  Compounds  of  Strontium. 

Strontium  oxide,  SrO,  is  produced  by  heating  strontium  nitrate. 
It  is  a  gray  mass  which  with  water  generates  heat  and  forms  strontium 
hydroxide. 

Strontium  hydroxide,  Sr(0H)2,  which  is  soluble  in  50  parts  water, 
can  be  obtained  as  crystalUne  Sr(OH)2  +  8H20  from  this  solution.  On 
heating  it  decomposes  into  water  and  strontium  oxide. 

Strontium  salts  are  prepared  from  strontium  carbonate  by  treating 
it  with  the  respective  acid.  In  regard  to  their  use  in  the  manufacture  of 
sugar  see  Cane-sugar. 

b.  Detection  of  Strontium  Compounds. 
1.  They  give  a  beautiful  crimson-red  color  to  the  non-luminous 
flame  (use  in  fireworks),  and  the  spectrum  of  this  flame  shows  one 
orange  and  one  blue  line. 


226  .    INORGANIC  CHEMISTRY. 

2.  Sulphuric  acid  precipitates  white  crystalline  StSO^  from  even 
very  dilute  solutions  of  strontium  salts. 

3.  Barium. 

Atomic  weight  137.4= Ba. 
Occurs  only  combined  as  witherite,  BaCOj,  and  as  barite  or  heavy 
spar,  BaS04.  The  pale-yellow  metal,  having  a  specific  gravity  of  3.7 
and  melting  at  475°,  is  obtained  by  the  electrolysis  of  fused  barium 
chloride.  It  behaves  like  Ca  and  Sr,  but  is  more  readily  oxidized  and 
decomposes  water  more  readily. 

a.  Compounds  of  Barium. 

Barium  oxide,  BaO,  forms  a  pale-gray  amorphous  mass. 

Barium  hydroxide,  Ba(0H)2,  crystallizes  from  its  aqueous  solution 
as  Ba(OH)2+8H20  in  tetragonal  prisms. 

Both  of  these  are  obtained  like  the  corresponding  strontium  com- 
pounds and  have  the  same  properties.  Barium  hydroxide  is  soluble 
m  20  parts  water  (baryta-water)  and  fuses  without  decomposition  at  a 
red  heat. 

Barium  dioxide,  BaOg,  is  produced  by  heating  barium  oxide  in  a 
current  of  oxygen  to  about  350°.  On  heating  to  700°  it  decomposes 
again  into  barium  oxide  and  oxygen.  It  is  a  white  powder  insoluble 
in  water  and  has,  like  all  peroxides,  no  basic  properties.  With  dilute 
acids  BaOj  yields  HgOj  (p.  117),  which  decomposes  with  MnOg  into  water 
and  oxygen:  Mn02+Ba02  +  2H2S04=MnS04  +  BaSO,  +  2H20  +  20.  With 
concentrated  sulphuric  acid  BslO.^  produces  oxygen  containing  ozone 
(p.  110).  Potassium  f erricyanide  (which  see) ,  as  well  as  all  salts  of  the  heavy 
metals,  develops  oxygen  from  BaOg  in  the  presence  of  water. 

Bariimi  salts  are  obtained  from  barium  carbonate  by  decomposition 
with  the  respective  acids,  evaporating  and  recrystallizing. 

Bariimi  chloride,  BaCl2  +  2H20,  forms  coloiless  rhombic  crystals 
which  are  soluble  in  water. 

Barium  sulphate,  BaS04,  is  used  as  a  paint  (permanent  white),  also 
mixed   with   basic   lead   carbonate    (Venetian,   Hamburg,  Dutch  white). 

b.  Detection  of  Barium  Compounds. 

1.  They  give  a  yellowish-green  color  to  the  non-luminous  flame, 
and  the  spectrum  of  this  flame,  which  is  rich  in  hnes,  gives  one  prom- 
inent pale-green  Hne. 

2.  Sulphuric  acid  precipitates  from  even  very  dilute  solutions  of 
barium  salts  white  amorphous  barium  sulphate,  BaSOi,  insoluble  in 
acids. 

3.  Potassium  chromate  precipitates  yellow  barium  chromate, 
BaCr04;  hydrofluosiUcic  acid  precipitates  white  BaSiF,  from  barium 
salt  solutions.  Both  are  insoluble  in  acetic  acid.  Ca  and  Sr  salts 
are  not  precipitated  by  these  reagents. 


BERYLLIUM.  227 

MAGNESIUM  GROUP. 
Beryllium.     Magnesium.     Zinc.     Cadmium. 

These  are  divalent  metals  which  are  volatile  on  heating  and  which 
burn  with  a  flame  into  oxides  when  air  is  supplied.  Their  specific  gravity, 
fusibility,  and  volatility  increase  with  their  atomic  weights.  They  do 
not  oxidize  on  being  exposed  to  dry  air.  Zinc  and  cadmium  do  not 
decompose  water  at  the  boiling  temperature,  beryllium  and  compact 
magnesium  only  with  difficulty,  while  they  all  decompose  water  at  a 
red  heat.  Their  oxides,  hydroxides,  carbonates,  and  phosphates  are  insolu- 
ble in  water,  and  their  sulphates  are  readily  soluble  in  water.  The  sul- 
phides of  beryllium  and  magnesium  are  soluble  in  water,  while  zinc  and 
cadmium  sulphide  are  insoluble  therein.  The  oxides  of  beryllium  and 
magnesium  are  not  reduced  to  the  metallic  state  by  carbon.  The  car- 
bonates and  chlorides  are  readily  decomposed  to  the  basic  salts  on 
warming. 

Their  sulphates  (with  the  exception  of  berylHum  sulphate)  form 
isomorphous  double  salts,  which  are  readily  soluble,  with  the  alkali  sul- 
phates: MgS04  4-K2S04  +  6H20.  Their  hydroxides  are  soluble  in  ammo- 
nia or  ammonium  salts. 

I.  Beryllium  (Qlucinum). 
Atomic  weight  9.1=  Be. 

Occurs  only  combined  in  certain  rare  minerals;  thus  in  phenacite, 
BcaSiO^,  in  chrysoberyl,  Be(A102)2,  ^^^  especially  in  beryl,  (Be3Al2)Si^O,g, 
which  when  colored  green  with  chromium  oxide  forms  the  precious 
stone  called  the  emerald. 

The  metal  is  prepared  by  heating  its  chloride  with  sodium  or  its  oxide 
with  aluminium.  It  forms  a  silver-white  metal  having  a  specific  gravity  of 
1.8  and  melting  at  about  1000°,  and  the  metal  with  its  salts  gives  no  colora- 
tion to  the  flame  and  no  spectrum.  The  copper  alloy  of  beryllium  gives 
a  beautiful  tone  when  struck  and  is  used  for  technical  purposes. 

Ammonia  or  caustic  alkali  precipitates  Be(0H)2  from  its  sweet  salt 
solution,  this  precipitate  being  soluble  in  an  excess  of  caustic  alkali. 
Ammonium  carbonate  precipitates  BeCO,,  which  is  soluble  in  an  excess 
of  (NH,)2C03. 

2.  Magnesium. 

Atomic  weight  24.36= Mg. 
Occurrence.     Only    combined:     1.  As    carbonate    in    magnesite, 
MgCOg,  and  dolomite,  MgCOg+CaCOa. 

2.  As  silicate,  forming  the  minerals  olivine,  talc,  soapstone,  serpen- 
tine, meerschaum.  Powdered  talc,  a  white  greasy  powder,  is  used 
as  a  vulnerary  powder.  Magnesium-calcium  silicate  forms  the 
minerals  augite,  hornblendes,  and  asbestus  (amianthus);  magnesium- 
aluminium  silicate,  chlorite  and  magnesium  mica. 

3.  As  sulphate  and  chloride  in  sea-water  and  in  certain  mineral 
waters,  giving  a  bitter  taste  thereto.    In  the  "  abraum  "  salts  (p.  202) 


228  INORGANIC  CHEMISTRY. 

they  occur  as  carnallite,  MgCl2+ KC1+ 6H2O,  kainite,  K2SO4+ 
MgSO^+MgCl^+GH^O,  kieserite,  MgSO^+H^O,  schonite,  MgS04+ 
K2SO4+6H2O,  boracite,  4MgB407+2MgO+MgCl2. 

4.  As  phosphate  and  carbonate  in  the  vegetable  and  anrnial  king- 
doms, especially  in  the  seeds  and  bones.  Many  animal  concretions, 
such  as  urinary  and  intestinal  calcuh,  consist  of  ammonium-magnesium 
phosphate,  Mg(NH4)P04,  which  also  occurs  in  guano. 

Preparation.  By  heating  magnesium  chloride  with  sodium  or  by 
the  electrolysis  of  fused  magnesium  chloride  or  carnallite. 

Properties.  Silver-white  metal,  non-oxidizable  in  dry  air,  having 
a  specific  gravity  of  1.75  and  which  can  be  hammered,  drawn  into 
wire,  and  cast  into  various  shapes.  Magnesium  melts  at  800°  and 
vaporizes  at  about  1100°.  When  heated  with  air  it  burns  with  a 
dazzling  white  Hght  which  is  rich  in  actinic  rays.  This  Hght  is 
produced  by  the  non-volatile  MgO,  becoming  incandescent  (used  in 
fireworks  and  photography).  Dilute  acids  dissolve  magnesium 
readily  with  the  generation  of  hydrogen.  On  boiling  magnesium 
with  water  hydrogen  is  slowly  generated.  Alkahes  do  not  attack 
this  metal.  It  is  a  strong  reducing  agent  and  removes  the  oxygen 
from  most  metallic  oxides  and  many  acid  anhydrides  on  being  heated 
therewith.  On  being  heated  white-hot  it  absorbs  nitrogen  and 
eventually  also  argon  (p.  182). 

a.  Alloys  with  Magnesium. 

The  alloy  with  aluminium,  magnalium,  is  used  for  technical 
purposes,  and  with  zinc  for  fireworks. 

b.  Compounds  of  Magnesium. 

Magnesium  oxide,  MgO,  magnesia,  bitter-earth,  is  obtained  by 

heating  magnesium   carbonate  or  magnesium   hydroxide.     It   is  a 

white,  amorphous,  infusible,  very  hght  powder  which   is   insoluble 

in  water.     When  gently  heated  with  water  it  forms  Mg(0H)2. 

At  higher  temperatures  it  conducts  electricity  and  shines  with  an 
intense  light  (Nernst  light).  This  light  is  produced  by  passing  the  elec- 
tric current  through  pencils  of  MgO  which  are  previously  heated. 

Magnesium  hydroxide,  Mg(0H)2,  is  formed  on  treating  a 
magnesium  salt  solution  with  caustic  alkali  (preparation  of  the 
metaUic  hydroxides).  It  forms  a  white  amorphous  powder  which 
is  nearly  insoluble  in  water  and  which  decomposes  on  heating  into 
MgO+H^O. 


I 


MAGNESIUM.  229 

Magnesium  chloride,  MgClg.  It  occurs  as  stated  on  pages  221  and  228 
and  is  obtained  as  a  by-product  in  many  chemical  processes.  It  crystallizes 
with  6H2O,  forming  deliquescent  crystals  which  on  evaporation  decom- 
pose and  are  used  in  the  manufacture  of  hydrochloric  acid  and  chlorine 
(p.  133).  It  may  be  obtained  in  an  anhydrous  form  by  heating  the  magne- 
smm  chloride  containing  water  in  the  presence  of  NH4CI  or  in  a  current 
of  hydrochloric  acid. 

Magnesium  sulphate,  MgSOi.  Occurrence,  As  kieserite,  also 
in  kainite  and  schonite  (p.  228);  in  sea-water  and  many  mineral 
waters,  to  which  it  gives  a  bitter  taste. 

Preparation.  By  dissolving  magnesium  carbonate  in  dilute 
sulphuric  acid,  or  by  boiling  kieserite  for  a  long  time  with  water, 
which  gradually  dissolves  the  same. 

Properties.  On  evaporating  its  aqueous  solution  it  is  obtained 
as  neutral,  colorless,  rhombic  crystals  having  the  composition  MgSOiH- 
7H2O.  It  has  a  disagreeable,  bitter  taste  and  is  soluble  in  1.5  parts 
by  weight  of  cold  water  (Epsom  salts). 

At  70°  MgS04  +  6H20  crystallizes  from  its  saturated  solution,  and 
at  0°  MgS04  +  12H20.  Kieserite,  MgSO^  +  HaO,  is  soluble  only  in  400 
parts  water,  but  it  gradually  dissolves  on  boiling  with  water  and  then 
crystaUizes  as  MgS04  +  7H20. 

On  heating  to  100°  Epsom  salts  lose  5  molecules  of  water,  forming 
MgS04  +  2H20,  and  at  150°  they  lose  still  another  molecule,  the  last 
molecule  being  driven  off  only  at  260°  (water  of  constitution,  p.  115). 

With  the  sulphates  of  the  alkali  metals  magnesium  sulphate  forms 
double  salts  (p.  102),  which  crystallize  in  monoclinic  prisms,  whereby 
the  firmly  combined  molecule  of  water  of  crystallization  is  replaced  thus: 

Potassium-magnesium  sulphate ,     MgS04  +  KjSO^         +  6H2O ; 
Ammonium-magnesium  sulphate,  MgS04  +  (NH4)2S04  +  6H20. 

The  sulphates  of  zinc,  cadmium,  manganese,  iron,  cobalt,  nickel,  which 
are  constituted  similarly  to  the  magnesium  sulphate,  are  all  isomor- 
phous,  and  also,  like  cupric  sulphate,  which  likewise  crystallizes  with  5  mole- 
cules H2O,  contain  1  molecule  H2O  firmly  combined.  These  all,  like 
mercuric  sulphate,  form  double  salts  which  have  an  analogous  composition 
and  are  isomorphous  with  double  magnesium  sulphates: 

NiS04+K2S04  +  6H20;  CuSO^  +  KaSO^  +  eH^O,  etc. 

Magnesium  carbonate,  MgCOg,  occurs  as  rhombohedra  in  mag- 
nesite  (isomorphous  with  calcite,  smithsonite,  rhodochrosite,  siderite, 
etc.),  and  in  crystalline  masses  as  magnesite,  also  in  dolomite  (p. 
223). 

If  carbon  dioxide  is  passed  into  water  containing  suspended 
basic  magnesium  carbonate  (see  below),  we  obtain  from  the  filtered 
solution,  on  standing,  neutral  magnesium  carbonate,  MgC03+  SH^O, 


230  INORGANIC  CHEMISTRY. 

as  colorless  crystals.     On  boiling  this  with  water  we  again  obtain 
basic  magnesium  carbonate. 

If,  on  the  contrary,  a  magnesium  salt  solution  is  precipitated 
with  alkali  carbonate,  we  do  not  obtain  the  normal  carbonate,  but 
the  basic  carbonate,  which  has  a  varying  composition,  dependent 
upon  the  concentration  and  temperature  of  the  liquids.  This  forms 
the  magnesium  carbonate  of  commerce  (magnesia  alba)  and  is  gen- 
erally given  the  following  formula:  4MgC03+Mg(OH)2+4H20. 
It  forms  a  white  porous  powder  which  ordinarily  occurs  in  cubes, 
and  which  is  insoluble  in  water  and  on  heating  decomposes  into 
MgO+COj+HA 

c.  Detection  of  Magnesium  Compounds. 

1.  They  are  colored  red  when  moistened  with  a  cobalt  salt  solu- 
tion and  heated  on  charcoal. 

2.  They  differ  essentially  from  the  compounds  of  the  alkaline 
earths  by  the  solubility  of  their  sulphate,  their  precipitation  by 
ammonia,  as  well  as  by  their  behavior  in  the  presence  of  ammonium 
salts  (see  3). 

3.  The  tendency  of  the  magnesium  salts  to  form  soluble  double 
compounds  with  ammonium  salts  is  the  reason  why  they  are  not 
precipitated  by  carbonates,  nor  by  the  alkali  hydroxides,  nor  by 
ammonia  in  the  presence  of  sufficient  amounts  of  an  ammonium  salt. 

4.  A  mixture  of  sodium  phosphate  and  ammonia  produces  a 
white  crystaUine  precipitate  of  ammonium  magnesium  phosphate, 
Mg(NH4)P04+6H20,  in  magnesium  salt  solutions  containing  ammo- 
nium salts  in  solution.     This  double  salt  is  the  most  insoluble  salt  of 

magnesium  (p.  169). 

3.  Zinc. 

Atomic  weight  65.4=  Zn. 

Occurrence.  Only  combined,  especially  as  zinc  spar  or  smithsonite, 
ZnCOj,  as  zinc  silicate  or  willemite,  Zn2Si04+  HjO,  as  ordinary  cala- 
mine (zinc  silicate  and  carbonate),  as  zinc  blend  or  sphalerite,  ZnS, 
and  as  zincite,  ZnO.  Nearly  all  these  ores  contain  some  cadmium 
besides  zinc. 

Preparation.  By  heating  the  zinc  ore  in  the  air  (roasting)  zinc 
oxide  is  obtained,  and  this  on  being  heated  with  carbon  is  reduced 
(ZnO+C  =  Zn+CO).  The  zinc  volatilizes  and  is  collected  in  the 
receivers. 

At  first  the  receivers  are  so  cold  that  the  zinc  separates  as  a  powder, 


Z/iVC.  231 

mixed  with  some  zinc  oxide  (which  is  produced  by  the  air  present  at 
the  beginning  of  the  operation),  and  with  tlie  more  volatile  cadmiimi. 
The  powder,  which  is  called  zinc-aust,  is  used  as  a  reducing  agent  and 
also  in  the  preparation  of  cadmium. 

Properties.  Bluish-white  crystalline  metal  having  a  specific 
gravity  of  7.1  and  brittle  at  ordinary  temperatures,  malleable  and 
reliable  at  100°,  again  brittle  at  200°,  fusible  at  433°,  and  vaporizable 
at  920°.  The  vapor  of  zinc  inflames  in  the  air. and  burns  into 
zinc  oxide  with  a  greenish  flame. 

Zinc  becomes  coated  in  moist  air  with  basic  zinc  carbonate,  and 
on  account  of  its  stabihty  in  the  air  it  is  used  as  rolled  sheet  zinc  or 
as  a  coating  to  sheet  iron  (galvanized  iron).  Zinc  in  pieces  decom- 
poses water  only  at  a  red  heat,  while  zinc-dust  gradually  decomposes 
water  at  ordinary  temperatures. 

Dilute  acids  dissolve  zinc  with  rapidity,  according  to  the 
amount  of  impurities  it  contains  (p.  104);  thus  pure  zinc  is  hardly 
attacked.  With  nitric  acid  no  generation  of  hydrogen  takes  place, 
as  the  hydrogen  produced  reduces  the  nitric  acid  (p.  160).  On  heating 
zinc  with  concentrated  sulphuric  acid  sulphur  dioxide  is  produced,  and 
on  heating  with  caustic  alkalies  it  dissolves  with  the  development  of 
hydrogen  (p.  104).  Zinc  precipitates  the  metal  as  a  powder,  and 
often  in  a  spongy  form,  from  the  solutions  of  salts  of  copper,  lead, 
tin,  silver,  gold,  platinum,  etc. 

a.  Alloys  of  Zinc. 

See  Copper  and  Nickel. 

b.  Compounds  of  Zinc. 

Zinc  oxide,  ZnO,  is  formed  on  burning  zinc  in  the  air  (zinc-white, 
flowers  of  zinc)  or  by  heating  zinc  carbonate.  It  is  a  white  amorphous 
powder  which  is  insoluble  in  water  and  which  becomes  momentarily 
yellow  on  being  heated. 

Zinc  hydroxide,  zinc  hydrate,  Zn(0H)2,  is  precipitated  from  zinc 
salt  solutions  by  caustic  alkalies  or  ammonia.  It  forms  a  white 
precipitate  which  is  soluble  in  an  excess  of  the  precipitant :  ZuSO^H- 
2KOH  =  Zn(OH)2+K2S04.  On  heating  it  decomposes  into  zinc 
oxide  and  water. 

Zinc  chloride,  ZnCl^,  is  produced  by  dissolving  zinc  in  hydro- 
chloric acid  and  carefully  evaporating  the  solution.  It  forms  a 
white  caustic  mass  which  deliquesces  in  the  air  and  is  readily  soluble 
in  water  and  alcohol.     It  also  occurs  in  commerce  cast  in  sticks. 


232  INORGANIC  CHEMISTRY, 

On  evaporation  it  behaves  like  MgClg  (p.  229).  It  crystallizes  from 
strong  hydrochloric  acid  solution  as  ZnCla  +  HgO,  and  with  zinc  oxide  it 
forms  a  plastic  mass  which  soon  hardens  and  is  used  by  dentists  in  filling 
teeth.     It  absorbs  ammonia  with  the  formation  of  ZnClg-NHg. 

Zinc  sulphate,  ZnS04,  white  vitriol,  with  THjO,  is  chiefly  pre- 
pared by  gently  roasting  zinc  blende  (ZnS)  and  extracting  the 
residue  with  water  and  evaporating  or,  in  a  purer  form,  by  dissolving 
zinc  in  dilute  sulphuric  acid.  It  forms  white  acid-reacting  crystals 
which  are  isomorphous  with  magnesium  sulphate  and  like  these  form 
double  salts  with  the  alkali  sulphates.  Zinc  sulphate  dissolves  in 
0.6  part  by  weight  of  water. 

Zinc  carbonate,  ZnCOj,  occurs  as  smithsonite,  isomorphous  with 
magnesium  carbonate,  etc.  (p.  229).  On  precipitating  zinc  salt  solu- 
tions with  alkali  carbonates  a  white  precipitate  of  basic  zinc  car- 
bonate is  formed  analogous  to  the  magnesium  salts.  Its  composition 
is  dependent  upon  the  concentration  and  temperature  of  the  solutions; 
thus  it  may  be  ZnC03+2Zn(OH)2  or  ZnCOg+SZnCOH),. 

c.  Detection  of  Zinc  Compounds. 

1.  On  being  moistened  with  a  cobaltous  salt  solution  and  heated 
on  charcoal  in  a  blowpipe  flame  they  give  a  beautiful  green  infusible 
mass  (ZnO.CoO),  which  is  also  used  as  an  artist's  pigment  (Rinmann's 
green,  Saxony  green). 

2.  Ammonium  sulphide  precipitates  white  zinc  sulphide  from 
zinc  salt  solutions:  ZnS04+(NHJ,S=ZnS+(NH,)2S04.  This  ZnS 
is  insoluble  in  acetic  acid,  but  is  soluble  in  dilute  mineral  acids  and 
is  used  mixed  with  BaS04  as  a  white  paint  Oithopone,  zincolith). 

3.  The  precipitate  of  Zn(0H)2  produced  by  alkali  hydroxides  is 
soluble  in  an  excess  of  the  alkali  hydroxide. 

4.  The  spark-spectrum  shows  a  series  of  lines,  amongst  which 
those  in  the  red  and  blue  are  most  striking. 

4.  Cadmium. 

Atomic  weight  112.4=Cd. 

Occurs  only  in  combination  in  small  amounts  in  the  zinc  ores,  and 
rarely  as  greenockite,  CdS.  It  is  obtained  by  distilling  zinc-dust  (p. 
231)  with  charcoal  and  then  redistilling  the  metal  obtained.  It  forms 
a  white  tough  metal  having  a  specific  gravity  of  8.6,  melting  at  315°, 
and  boiling  at  778°  (zinc  at  1040°). 

a.  Alloys  of  Cadmium. 
See  mercury  and  lead. 


I 


COPPER.  233 

h.  Compounds  of  Cadmium, 

These  are  obtained  in  ttie  same  manner  as  the  corresponding  zinc 
compound. 

Cadmium  oxide,  CdO,  is  obtained  by  heating  cadmium  nitrate.  It 
is  a  brown  microcrystalline  powder. 

Cadmium  hydroxide,  Cd(0H)2  is  precipitated  from  cadmium  salt  solu- 
tions by  caustic  alkalies  or  ammonia  as  a  white  powder  which  is  soluble 
in  ammonia  but  not  in  caustic  alkali,  and  when  heated  decomposes  into 
CdO  +  H^O. 

Cadmium  sulphate,  3CdS04  +  8H20,  crystaUizes  only  at  —20°  with 
7H2O,  but  forms  double  salts  with  alkali  sulphates,  corresponding  to  the 
magnesium,  zinc,  etc.,  salts  (p.  229). 

c.  Detection  of  Cadmium  Compounds. 

1.  On  passing  H2S  into  a  solution  of  cadimum  salt  a  beautiful  yellow 
precipitate  of  CdS  is  obtained.  This  is  insoluble  in  (NH4)2S,  which  differs 
from  the  yellow  sulphides  of  tin  and  arsenic.  This  sulphide  is  used  as  a 
pigment  (cadmium  yellow). 

2.  When  heated  with  soda  on  charcoal  the  cadmium  compounds  give 
a  brown  crust  of  cadmium  oxide,  CdO. 

3.  The  spark-spectrum  gives  characteristic  bright  lines. 

SILVER  GROUP. 
Copper.  Silver.  Mercury. 
These  metals  appear  as  monovalent,  copper  and  mercury  also  as  divalent. 
They  do  not  decompose  water  even  at  a  red  heat,  and  are  not  dissolved 
by  hydrochloric  acid  or  dilute  sulphuric  acid,  but  are  readily  dissolved 
by  nitric  acid  or  concentrated  sulphuric  acid.  Their  sulphides  are  insol- 
uble in  dilute  acids,  and  the  halogen  compoimds  of  the  monovalent  series 
are  insoluble  in  water.  The  hydroxides  of  copper  decompose  even  at  100° 
in  the  presence  of  water,  while  the  hydroxides  of  silver  and  mercury  are 
not  known.  With  alkali  sulphates  the  sulphates  of  the  metals  of  the 
divalent  series  form  double  salts  which  are  isomorphous  and  correspond 
with  those  of  the  magnesium  group. 

I.  Copper  (Cuprum). 

Atomic  weight  63.6=  Cu. 

Occurrence.  Native  in  large  quantities,  especially  in  America 
and  Siberia,  often  crystallized  in  cubes  or  octahedra.  The  most 
common  copper  ores  are  red  copper  ore  (cuprite),  CU2O,  copper 
glance  (chalcocite),  CujS,  azurite,  2CuC03+Cu(OH)2,  malachite^  CuCO, 
+  Cu(0H)2,  chalcopyrite  or  copper  pyrites,  CujS+FojSg,  and  the 
tetrahedrite  group  (Fahl  ores)  (p.  181).  Traces  of  copper  are  found 
in  most  plants  and  animals. 

Preparation.  1.  Native  copper  is  obtained  from  the  ores  by  stamp- 
ing them  and  then  washing  with  water.  The  granular  masses  obtained 
are  refined  by  melting  in  the  presence  of  small  quantities  of  carbon. 

2.  From  its  oxides  and  carbonates  by  reduction  with  carbon: 
CuC03+2C  =  Cu+3CO. 


234  INORGANIC  CHEMISTRY. 

3.  Copper  can  be  obtained  from  the  sulphides  only  with  difficulty, 
as  the  iron  and  other  impurities  must  first  be  removed. 

a.  The  sulphides  are  roasted  with  air  until  a  great  part  of  the  foreign 
metallic  sulphides  (p.  127)  are  transformed  into  oxides,  while  a  part  of 
the  copper  sulphide  is  also  oxidized. 

b.  The  mass  thus  obtained  is  fused  with  carbon  and  siUcates,  when 
the  copper  is  reduced  on  account  of  its  low  affinity  for  oxygen,  while  the 
other  oxides  are  in  great  part  dissolved  by  the  fused  silicates,  which  are 
removed  as  a  slag.  The  copper  combines  with  the  metaUic  sulphides 
still  present  and  collects  on  the  bottom  of  the  furnace  as  coarse  metal 
(containing  about  32  per  cent.  Cu). 

c.  This  is  roasted  in  turn  and  again  fused  with  carbon  and  silicates.  A 
part  of  the  foreign  metallic  oxides  is  here  reduced  to  the  metallic  state; 
it  no  longer  forms  a  slag,  but  unites  with  the  metallic  copper,  forming 
the  so-called  black  copper  (containing  about  95  per  cent.  Cu). 

d.  This  black  copper  is  fused  on  a  blast-hearth,  when  the  foreign 
metals  oxidize  more  readily  than  the  copper,  separate  on  the  surface,  and 
are  removed. 

e.  Or  the  black  copper  is  suspended  as  the  anode  in  a  cupric  sulphate 
solution  and  the  copper  dissolved  by  the  electric  current  and  deposited 
on  the  cathode,  consisting  of  a  pure  copper  plate,  while  the  impurities 
separate  out  as  a  slime. 

4.  In  the  wet  way,  by  converting  the  copper  ore  into  cupric 
sulphate  (which  see)  by  roasting,  or  into  cupric  chloride  by  roasting 
with  alkali  chlorides  and  then  precipitating  the  copper  from  these 
watery  solutions  by  means  of  iron;  thus,  CuSO^+Fe^FeSO^-l-Cu; 
CuCl2-hFe  =  FeCl2+Cu. 

5.  Chemically  pure  copper  can  be  obtained  by  reducing  heated 
copper  oxide  in  a  current  of  hydrogen  or  by  decomposing  a  copper 
salt  solution  by  the  electric  current. 

Properties.  Red,  very  ductile  and  tough  metal  having  a  specific 
gravity  of  8.9  and  unacted  upon  in  dry  air,  but  becoming  in  moist  air, 
coated  with  green  basic  carbonate  (verdigris).  On  being  heated  in  the 
air  it  is  coated  with  a  black  layer  of  cupric  oxide  and  melts  at  1065°.  It 
is  insoluble  in  hydrochloric  acid  and  dilute  sulphuric  acid,  but  gradu- 
ally dissolves  when  moistened  therewith  and  exposed  to  the  air,  when 
oxygen  is  absorbed.  Copper  dissolves  in  hot  concentrated  sulphuric 
acid,  forming  cupric  sulphate  with  the  production  of  sulphur  dioxide 
(p.  124)  and  in  dilute  nitric  acid  with  the  generation  of  nitric 
oxide  (p.  156).  Metallic  copper  can  be  separated  from  its  aqueous 
solutions  by  iron,  zinc,  and  phosphorus. 

Univalent  copper  forms  cuprous  compounds,  and  bivalent  copper 
forms   cupric   compounds.     All   cupric   compounds   are   blue   when 


COPPER.  235 

dilute,  as  they  all  have  the  same  cation,  Cu",  while  the  cation  Cu'  is 
colorless  as  cuprous  salts. 

a.  Alloys  of  Copper. 

Copper  cannot  be  cast,  as  on  coohng  it  contracts  irregularly  and 
hence  does  not  fill  the  mould.  With  zinc  or  tin  copper  forms  alloys 
which  can  be  cast. 

Alloys  of  copper  with  zinc.  Brass  is  a  golden-yellow  alloy  of  2 
parts  copper  and  1  part  zinc.  The  more  copper  it  contains  the 
redder  is  the  color,  and  the  more  zinc  the  whiter  is  the  product.  Such 
alloys  are  called  pinchbeck  or  red  metal,  talmi-gold,  Muntz  metal, 
impure  gold-leaf,  so-called  gold  foam,  etc. 

Alloys  of  copper  with  tin  are  called  bronzes.  We  differentiate 
between  gun-metal,  bell-metal,  speculum-metal,  antique  bronze. 
Modern  bronze  consists  of  copper,  tin,  and  zinc.  Copper  coins 
contain  95  per  cent,  copper,  4  per  cent,  tin,  and  1  per  cent.  zinc. 
Phosphorus  bronze  contains  0.5-0.8  per  cent.  P  and  is  very  hard  and 
stable.  Silicium  bronze  contains  0.5-0.8  per  cent.  Si,  is  very  hard, 
and  is  a  good  conductor  of  electricity. 

Alloys  of  copper  with  aluminium,  silver,  nickel,  manganese,  and 
gold  will  be  treated  of  in  connection  with  these  metals.  , 

b.  Cuprous  Compounds. 
Cuprous  oxide,  copper  suboxide,  CujO,  occurs  as  cuprite  and 
may  be  obtained  by  heating  a  cupric  salt  solution  with  glucose 
in  the  presence  of  caustic  alkali.  It  forms  a  red  crystalhne  powder 
which  is  not  changed  in  the  air  and  is  insoluble  in  water.  See  also 
cuprous  salts. 

Cuprous  hydroxide,  Cu(OH),  is  obtained  on  gently  heating  an  alka- 
line cupric  salt  solution  (see  below)  with  glucose,  or  by  treating  cuprous 
chloride  with  caustic  alkali.  It  forms  a  yellow  powder  which  quickly 
oxidizes  to  cupric  hydroxide. 

Cuprous  sulphide,  CugS,  occurs  as  copper  glance,  copper  pyrites,  etc., 
and  is  produced  on  burning  copper  in  sulphur  vapors,  as  well  as  by  heat- 
ing cupric  sulphide  in  the  absence  of  air  (2CuS=Cu2S  +  S),  or  in  a  current 
of  hydrogen. 

Cuprous  salts  are  known  only  of  oxygen-free  acids,  as  CuaO  dissolves 
in  oxygen  acids,  forming  cupric  salts,  with  the  separation  of  metallic 
copper:  Cu20  +  H2S04=CuS04  4-H20  +  Cu.  The  cuprous  salts  are  color- 
less, but  quickly  turn  green  or  blue  in  the  air,  due  to  the  absorption  of 
oxygen. 

The  haloid  cuprous  salts  are  insoluble  in  water.  Cuprous  chloride 
dissolves  readily  in  NHg  or  HCl,  and  both  of  these  solutions  absorb  CO 
(p.  189). 


236  INORGANIC  CHEMISTRY, 

c.  Cupric  Compounds. 

Cupric  oxide,  copper  oxide,  CuO,  obtained  by  heating  cupric 
nitrate  or  cupric  carbonate,  or  by  precipitating  a  boiling  cupric  salt 
solution  with  hot  caustic  alkali  or  alkali  carbonate  solution.  It  is  a 
black  amorphous  powder  which  does  not  change  on  heating,  but  which 
on  heating  with  carbon,  hydrogen,  or  organic  substances  gives  off  its 
oxygen;  hence  it  is  used  in  the  analysis  of  organic  bodies  (Part  III). 

Cupric  liydroxide,  copper  hydrate,  Cu(0H)2,  is  precipitated  from 
cupric  salt  solutions  by  caustic  alkahes  as  a  blue  amorphous  mass 
which  on  heating,  even  under  water,  decomposes  into  black  cupric 
oxide  and  water. 

The  presence  of  many  organic  substances  prevents  the  precipitation  of 
cupric  salts  by  alkalies.  A  clear  mixture  of  cupric  sulphate  with  tar- 
trates and  caustic  alkali  is  used  as  an  alkaline  copper  solution,  or  Fehling's 
solution,  for  the  detection  of  sugar  (which  see).  Cupric  oxide  and  cupric 
hydroxide  are  soluble  in  ammonia,  the  solution  becoming  deep  blue.  This 
solution  is  the  only  solvent  for  cellulose  (Schweitzer's  reagent). 

Cupric  sulphide,  copper  sulphide,  CuS,  is  precipitated  from  solu- 
tions of  cupric  salts  by  H^S  as  an  amorphous  brownish-black  powder 
insoluble  in  dilute  acids.  When  heated  in  the  absence  of  air  it  decom- 
poses into  cuprous  sulphide  and  sulphur,  and  when  moist  it  oxidizes  into 
cupric  sulphate. 

Cupric  sulphate,  Copper  Vitriol,  Blue  Vitriol,  CuSOi+SHjO. 
Preparation.  1.  On  a  large  scale  by  carefully  roasting  the  natural 
copper  sulphides,  which  are  thereby  converted  into  cupric  sulphate, 
while  the  iron  sulphide  is  in  great  part  converted  into  iron  oxide. 
On  lixiviating  with  water  a  cupric  sulphate  solution  comparatively 
free  from  iron  is  obtained  (crude).  This  is  purified  by  repeated 
recrystallization. 

2.  It  may  also  be  obtained  pure  by  dissolving  copper  in  concen- 
trated hot  sulphuric  acid  and  evaporating,  etc.: 

Cu+ 2H,S04  =  CUSO4+ SO2+ HA 

Properties.  Large  blue  triclinic  crystals  which  dissolve  in  2.5 
parts  water.  At  100°  they  lose  4  molecules  of  water  of  crystalliza- 
tion, and  at  200°  they  become  anhydrous  and  form  a  white  powder^ 
which  becomes  blue  again  with  the  slightest  amount  of  water  (detec- 
tion of  water  in  alcohol).  On  highly  heating  cupric  sulphate  it  decom- 
poses into  cupric  oxide,  sulphur  dioxide,  and  oxygen:  CuS04  =  CuO+ 
SO2+O.    With  alkali  sulphates  cupric  sulphate  yields  double   salts 


COPPER.  237 

which  are  analogous  in  composition  and  isomorphous  with  the  mag- 
nesium salts,  etc.: 

CUSO4+K2SO4+6H2O  (p.  229). 

Basic  cupric  sulphate  forms  the  color  called  Casselmann's  green. 
Copper  alum  is  a  fused  mass  of  cupric  sulphate,  alum,  camphor,  and 
potassium  nitrate. 

Cupric  ammonium  salts,  e.g., 

Cu<^^3>so,+a;NH3,         ChK^^^Cl  +  ^NHg, 

may  be  considered  as  ammonium  salts  in  which  2H  atoms  are  replaced 
by  a  divalent  Cu  atom.  They  contain  a  complex  ion  (p.  84)  with  a 
cupric  atom  (see  Cobalt  and  Platinum)  instead  of  a  cupric  ion. 

If  a  cupric  sulphate  solution  is  treated  with  ammonia,  a  blue  basic 
cupric  sulphate  is  precipitated.  This  dissolves  in  an  excess  of  ammonia, 
giving  a  deep-blue  liquid  from  which  deep-blue  prisms  of  (NH3)2CuS04  + 
2NH3  +  H2O  are  precipitated  by  alcohol. 

On  heating  this  salt  to  150°  it  loses  water  and  ammonia  and  a  green 
cupric  ammonium  sulphate,  (NH3)2CuSO^,  is  obtained. 

Cupric  chloride,  CuClg,  forms  pale-green  needles  with  2  mols.  water, 
and  is  yellowish  brown  when  anhydrous.  It  forms  double  salts  with  alkali 
chlorides. 

Cupric  arsenite,  CuHAsOg,  is  obtained  by  precipitating  a  cupric  salt 
with  potassium  arsenite,  as  a  beautiful  green  precipitate  which  is  used 
as  a  pigment,  called  Scheele's  green. 

Cupric  Carbonate,  CuCOj,  is  not  known.  If  a  cupric  salt  solu- 
tion is  treated  with  sodium  carbonate,  a  precipitate  of  the  green 
basic  cupric  carbonate,  3CuC03+3Cu(OH)2-FH20  or  CuCOa-t-CuCOH)^, 
is  obtained,  dependent  upon  the  temperature  and  concentration  of  the 
liquid.  This  compound  forms  the  color  Brunswick  green  and  occurs 
as  the  beautiful  green  mineral  malachite.  Verdigris,  patina,  copper, 
rust,  which  is  produced  by  the  action  of  air  and  water  upon  copper 
or  bronze,  has  the  same  composition.  2CuC03-|-Cu(OH)2  occurs 
as  the  beautiful  blue  mineral  azurite,  which  when  powdered  forms 
the  artist's  pigment  known  by  that  name. 

d.  Detection  of  Copper  Compounds. 

1.  They  give  a  green  or  blue  color  to  the  non-luminous  flame. 
The  spectrum  of  this  flame  contains  many  lines,  but  the  blue  and 
green  lines  are  characteristic. 

2.  Sulphuretted  hydrogen  precipitates  from  solutions  of  copper 
brownish-black  CuS,  which  is  insoluble  in  dilute  acids. 

3.  Ammonia  precipitates  greenish-blue  basic  salts  which  are 
soluble  in  excess  (see  above)  from  copper  solutions.     All  copper  com- 


238  INORGANIC  CHEMISTRY. 

pounds  with  the  exception  of  the  sulphide  are  soluble  with  blue 
coloration  in  an  excess  of  ammonia.  With  cuprous  compounds 
the  color  appears  only  after  standing. 

4.  Zinc  and  iron  deposit  metalhc  copper,  which  appears  as  a 
red  coating  on  the  metal. 

5.  Cuprous  compounds  are  characterized  by  the  insolubility  of 
their  halogen  compounds. 

2.  Silver  (Argentutn). 

Atomic  weight  107.93  =Ag. 

Occurrence.  Often  native  in  large  pieces,  but  especially  in  com- 
bination as  silver  glance,  argentite,  AgjS,  as  silver-copper  glance,  stro- 
meyerite,  Cu;;S+Ag2S,  as  stephanite,  AgjS+AgjSbSj,  as  proustite, 
AgjSbSj,  horn-silver,  AgCl,  and  in  the  Fahl  ores  (p.  181).  Lead  and 
copper  pyrites  often  contain  small  amounts  of  silver. 

Preparation.  Silver  glance  and  similar  ores,  which  contain  no 
other  metal,  need  only  to  be  roasted  and  melted.  All  other  ores 
containing  silver  require  complicated  methods  of  separation.  The 
silver  obtained  from  them  always  contains  several  per  cent,  of  foreign 
metals. 

1.  Amalgamation  Process.  This  is  used  in  Mexico  when  there  is  lack 
of  fuel. 

a.  The  ore  is  rubbed  up  with  common  salt,  cupric  sulphate,  and  water 
and  roasted,  when  the  silver  is  converted  into  silver  chloride. 

b.  The  mass  is  shaken  in  barrels  with  water,  iron  filings,  and  mercury. 
The  metallic  iron  converts  the  silver  chloride  into  metallic  silver:  2AgCl  + 
Fe=2Ag  +  FeCl2.  The  mercury  dissolves  the  separated  silver  (silver 
amalgam)  and  collects  at  the  bottom  of  the  barrel,  where  it  is  drawn  off. 
The  mercury  is  distilled,  leaving  the  silver  as  a  residue. 

2.  The  extraction  method  is  used  for  copper  ores  containing  silver. 
The  ore  or  the  copper-stone  containing  silver  (p.  233)  is  roasted  in  the  air, 
when  first  ferric  sulphate  and  then  cupric  sulphate  are  formed,  and  finally 
at  a  higher  temperature,  when  all  the  ferric  sulphate  and  a  part  of  the 
cupric  sulphate  are  decomposed  into  oxides,  silver  sulphate  is  formed. 
The  product  thus  obtained  is  extracted  with  hot  water,  which  dissolves 
the  silver  sulphate  and  any  cupric  sulphate  present,  and  the  silver  then  pre- 
cipitated from  this  solution  by  metallic  copper,  when  cupric  sulphate  is 
obtained  as  a  by-product :   AggSO^ + Cu  =  2 Ag + CuSO^. 

3.  The  lead  method  is  chiefly  applied  to  obtain  the  silver  that  is 
always  found  in  lead  pyrites,  the  lead  containing  silver  being  first 
prepared  from  the  ore  (see  Lead).  Other  ores  poor  in  silver  are  melted 
with  lead  or  lead  glance,  and  the  argentiferous  lead  prepared  there- 
from. 

If  the  lead  obtained  is  rich  in  silver  (|  per  cent.),  it  is  directly  exposed 
to  cupellation,  which  is  based  upon  the  fact  that  the  molten  lead  oxidizes 


SILVER,  239 

when  exposed  to  the  air,  but  the  molten  silver  does  not.  The  lead  is 
fused  and  air  is  blown  in  by  a  blast;  the  lead  is  converted  into  oxide  (litharge) 
which  melts  and  passes  off,  leaving  finally  the  unoxidized  silver  covered 
only  with  a  thin  layer  of  lead  oxide,  which  is  finally  ruptured,  and  the 
shining  silver  remains  behind. 

If  the  lead  contains  only  small  amounts  of  silver,  it  is  concentrated  by 
Pattinson's  or  Parke's  process.  Pattinson's  process  is  based  upon  the 
fact  that  a  molten  alloy  of  silver  and  lead  solidifies  slower  than  pure  lead. 
Hence  if  this  alloy  is  allowed  to  cool  slowly,  pure  lead  first  crystallizes  out, 
which  can  be  removed  by  perforated  ladles,  and  finally  a  eutectic  mixture 
containing  2.2  per  cent,  silver  remains. 

Parke's  process  is  based  from  the  fact  that  on  the  addition  of  zinc  to 
molten  lead  poor  in  silver  the  two  metals  do  not  mix  well  together,  but 
the  silver  leaves  the  lead  and  goes  over  to  the  zinc,  forming  a  difficultly 
fusible  alloy,  which  on  cooling  separates  on  the  surface.  The  zinc  is  sep- 
arated therefrom  by  distillation. 

Pure  silver  can  be  obtained  from  the  crude  silver  by  melting  it  with 
lead  and  then  driving  this  off,  or  by  dissolving  the  crude  silver  in  HNO3 
and  precipitating  all  the  silver  from  solution  as  AgCl  by  means  of  hydro- 
chloric acid,  and  reducing  this  as  described  on  p.  240. 

Pure  silver  may  moreover  be  obtained  by  dissolving  the  crude  sil- 
ver in  sulphuric  acid  and  precipitating  the  silver  with  copper  or  iron: 
Ag2S04  +  Fe=FeS04  +  Ag2;  also  by  electrolysis,  where  the  crude  silver  is 
suspended  as  the  anode  in  a  concentrated  solution  of  silver  nitrate,  when 
pure  silver  deposits  at  the  cathode,  which  consists  of  a  sheet  of  silver. 

Properties.  White,  shining,  rather  soft  metal  having  a  specific 
gravity  of  10.5  and  not  oxidizing  when  molten,  but  absorbing  22  times 
its  volume  of  oxygen,  which  it  gives  up  on  cooling:  this  causes  the 
sputtering  that  takes  place  when  fluid  silver  cools  Ozone  causes  a 
superficial  coating  of  silver  peroxide  (p.  240).  Silver  melts  at  960° 
and  vaporizes  at  about  2000°,  forming  a  pale-blue  vapor.  Concen- 
trated hydrochloric  acid  and  dilute  sulphuric  acid  do  not  attack  silver, 
but  hot  concentrated  sulphuric  acid  dissolves  it,  forming  silver  sul- 
phate :  2Ag+  2H,S04  =  Ag,S04+  SO2+  2H2O.  Dilute  nitric  acid,  even 
in  the  cold,  dissolves  silver,  producing  silver  nitrate :  3Ag+4HN03  = 
3AgN03+NO+2H20.  Silver  unites  directly  with  the  halogens; 
with  sulphur  it  combines  very  readily;  hence  silver  objects  turn 
black  when  exposed  to  air  containing  H^S.  Silver  is  very  ductile 
and  is  the  best  conductor  of  heat  and  electricity.  Thin  hammered 
sheets  are  called  silver-foil. 

Silver  only  occurs  univalent,  hence  the  designation  argentous 
and  argentic  salts  is  not  used.  The  silver  compounds  have  the 
same  composition  as  the  cuprous  compounds. 

There  are  also  certain  allotropic  modifications  of  silver,  namely,  a 
bluish-green  and  a  golden-yellow  form,  which  are  very  quickly  transformed 


240  INORGANIC  CHEMISTRY. 

into  ordinary  silver.  On  the  reduction  of  silver  chloride  we  obtain  a  fine 
gray  powder,  so-called  molecular  silver,  while  on  heating  silver  citrate  we 
obtain  the  so-called  colloidal  silver  as  a  brownish-black  powder  which 
forms  a  deep-red  pseudo-solution  with  water  (p.  53) 

a.  Alloys  of  Silver, 
Silver  is  too  soft  to  be  worked  as  such.  A  small  addition  of 
copper  makes  it  harder  without  changing  its  white  color.  Ordinary 
silverware  contains  12  parts  silver  in  every  16  parts,  or  75  per  cent. 
At  the  present  time  we  generally  express  the  amount  of  silver  in  the 
alloy  in  parts  per  thousand.  German,  French,  Austrian,  and  United 
States  silver  coins  have  a  fineness  of  iVxnr,  and  the  English  coins 
^Vy    or  sterling. 

b.  Compounds  of  Silver. 

Silver  oxide,  AggO,  is  obtained  by  treating  a  silver  salt  solution  with 
caustic  alkali,  producing  a  dark-brown  amorphous  precipitate,  which 
when  moist  is  a  strong  base  and  behaves  like  AgOH.  On  heating  it 
splits  into  silver  and  oxygen. 

Silver  hydroxide,  Ag(OH),  is  obtained  as  a  white  powder  on  mixing 
an  alcoholic  solution  of  a  silver  salt  with  alcoholic  caustic  alkali  at  —40°. 
At  ordinary  temperatures  it  decomposes  into  AggO  +  H^O. 

Silver  peroxide,  AgaOa,  is  formed  by  the  action  of  ozone  upon  AgjO. 
It  is  a  black  crystalline  powder. 

Silver  sulphide,  AggS,  occurs  as  octahedrons  in  silver  glance  and  is  pro- 
duced by  passing  H^S  into  a  silver  salt  solution.  It  is  an  amorphous 
black  precipitate  which  is  insoluble  in  dilute  acids. 

Silver  chloride,  chloride  of  silver,  AgCl,  occurs  in  octahedra  as  horn- 
silver,  and  is  obtained  by  precipitating  a  silver  salt  solution  with 
hydrochloric  acid  or  a  soluble  chloride.  It  forms  an  amorphous, 
white,  cheese-like  precipitate: 

AgN03+  HQ  =  Aga+  HNO3 ; 

AgN03+  KCl  =  AgCl+  KNO3. 
When  exposed  to  light  it  turns  violet  and  then  black,  when  it  decom- 
poses into  chlorine  and  silver  subchloride,  AgjCl.  Silver  chloride  is 
insoluble  in  acids,  but  readily  soluble  in  ammonia,  potassium  cyanide, 
and  sodium  hyposulphite.  Nascent  hydrogen  (zinc  and  HCl)  readily 
reduces  it  into  the  metal,  and  fusion  Avith  alkali  carbonate  produces 
the  same  change.  The  silver  carbonate  first  formed  is  decomposed 
by  the  heat  with  separation  of  metaUic  silver:  2AgCl+ NajCOj  =» 
Ag2C03+2NaCl;  Ag,C03=2Ag+C02+0. 

Silver  bromide,  AgBr,  is  obtained  by  treating  a  silver  salt  solu- 
tion with  HBr  or  a  bromide,  producing   a  yellowish-white  precipi- 


SILVER.  241 

tate  having  the  same  properties  as  silver  chloride,  although  not  as 
soluble  in  ammonia.  i 

Silver  iodide,  Agl,  is  obtained  by  keating  a  silver  salt  solution 
with  HI  or  an  iodide,  producing  a  yellowish  precipitate  having  similar 
properties  as  silver  chloride,  but  insoluble  in  ammonia,  and  is  sensitive 
to  Hght  in  the  presence  of  silver  nitrate. 

The  art  of  photography  depends  upon  the  fact  that  light  causes  a 
transformation  of  the  haloid  salts  of  silver  into  silver  subhaloid  salts, 
i.e.,  AggCl,  which  by  certain  reducing  agents  (developers)  are  readily 
reduced  to  silver,  while  the  unchanged  haloid  silver  is  not  acted  upon 
by  the  developer.  After  development  of  the  picture,  in  order  to  make 
it  permanent  it  must  be  "fixed"  by  placing  it  in  a  solution  of  com- 
pounds (generally  sodium  hyposulphite),  which  dissolves  the  undecom- 
posed  and  still  sensitive  haloid  silver  compounds.  At  the  present  time 
plates  covered  with  silver  bromide  (by  the  aid  of  gelatine)  are  chiefly 
used,  as  this  is  more  stable  and  more  sensitive  to  light  than  plates  covered 
with  silver  iodide  and  chloride.  Silver  iodide  can  be  used  only  when  wet; 
while  silver  chloride  is  generally  used  for  printing-paper. 

Silver  hydrazoate,  NgAg,  and 

Silver  amid,  2NH2Ag-f-H20,  silver  fulminate,  produced  when  freshly 
precipitated  silver  oxide  is  treated  with  a  concentrated  solution  of  ammo- 
nia, both  explode  when  dry  with  slight  friction. 

Silver  nitrate,  AgNO^,  is  prepared  by  dissolving  silver  in  nitric 
acid  (p.  239)  and  evaporating  the  solution.  It  forms  colorless  rhombic 
crystals  which  dissolve  in  1  part  by  weight  of  water  or  4  parts  of 
alcohol.  It  has  a  caustic  action  and  blackens  in  contact  with  organic 
substances  (skin,  linen,  etc.).  Silver  nitrate  melts  at  200°,  and  on 
further  heating  it  decomposes  into  silver  nitrite,  AgNOj,  and  oxygen, 
and  finally  into  silver,  nitrogen,  and  oxygen. 

It  is  moulded  when  hot  into  sticks  which  are  called  lunar  caustic, 
Lapis  inf emails.  On  fusion  with  two  parts  of  potassium  nitrate  we 
obtain  mitigated  caustic. 

c.  Detection  of  Silver  Compounds. 

1.  When  fused  on  charcoal  with  soda  they  yield  a  silver  globule. 

2.  All  silver  compounds  with  the  exception  of  the  iodide  and 
sulphide  are  readily  soluble  in  ammonia. 

3.  Hydrochloric  acid  or  a  soluble  chloride  precipitates  white, 
cheese-like  silver  chloride  from  solutions  of  silver.  This  precipitate 
is  soluble  in  ammonia,  insoluble  in  acids,  and  darkens  in  the  light. 

4.  Metallic  zinc,  iron,  copper,  and  mercury  precipitate  metallic 
silver  from  its  solutions. 


242     .  INORGANIC  CHEMISTRY. 

3.  Mercury  (Hydrargyrum  or  Quicksilver). 

Atomic  weight  200=  Hg. 

Occurrence.  Native  to  -a  slight  extent,  but  chiefly  as  cinnabat 
(HgS)  in  Almaden,  Idria,  California,  etc.  It  is  also  found  in  many 
Fahl  ores  (p.  181). 

Preparation.  Generally  by  roasting  cinnabar  with  access  of  air: 
HgS+20=Hg+S02.  The  vapors  of  mercury  formed  are  passed 
into  a  cooled  chamber,  where  they  condense. 

Pure  mercury  is  obtained  by  treating  the  commercial  quicksilver  with 
a  ferric  chloride  solution  or  cold  dilute  nitric  acid,  which  dissolve  the 
contaminating  metals  more  readily  than  the  mercury.  The  mercury  may 
also  be  purified  by  squeezing  it  through  leather  and  then  distilling  in 
vacuum.  When  pure  it  flows  over  smooth  surfaces  as  shining,  round 
drops,  but  when  impure  it  forms  mat,  elongated  drops. 

Properties.  Mercury  is  the  only  liquid  metal;  at  ordinary  tem- 
peratures it  is  silver-white,  has  a  specific  gravity  of  13.5,  solidifies  at 
'  —  39°,  and  boils  at  357°,  but  volatilizes  even  at  ordinary  temperatures, 
yielding  vapors  which  are  poisonous.  It  is  unchanged  in  ttte  air, 
but  if  it  is  heated  in  the  neighborhood  of  its  boiling-point  it  turns 
into  red  crystalline  mercuric  oxide  (p.  244).  Mercury  is  insoluble 
in  hydrochloric  acid  and  cold  sulphuric  acid;  moderately  warm 
nitric  acid  dissolves  an  excess  of  mercury,  forming  mercurous  nitrate: 
3Hg+4HN03=3HgN03+2H,0+NO;  white  hot  nitric  acid  in 
excess  dissolves  mercury,  forming  mercuric  nitrate :  3Hg+  8HNO3  = 
3Hg(N03)2+4H204-2NO.  Sulphuric  acid  also  forms  mercurous 
or  mercuric  sulphate  under  the  same  conditions: 

2Hg+  2H2SO4  =  Hg2S04+  2H2O+  SO2; 

Hg+2H,S04  =HgS04+2H204-S02. 

On  shaking  with  air,  water,  etc.,  or  by  rubbing  with  sugar,  fat,  etc., 
mercury  can  be  obtained  finely  divided,  so  that  it  forms  a  gray  powder 
which  prevents  the  coalescing  of  the  layers  of  air,  water,  fat,  etc.,  between 
the  drops.  On  rubbing  mercury  with  two  parts  fat  we  obtain  gray  mer- 
cury salve.  Mercury  is  also  known  as  a  black  powder  which  gives  a 
brown  pseudo-solution  with  water  (p.  53)  and  which  is  used  in  medicine 
as  hyrgol,  or  colloidal  mercury. 

The  compounds  of  mercury  are  mostly  poisonous  and  have  an 

analogous  composition  and  nomenclature  as  the  copper  compounds. 

a. -Alloys  of  Mercury 

are   called   amalgams  and  are    obtained  by  the    direct   union  with 

the  metals.      Most  metals   dissolve  in  mercury  even  in  the  cold. 


MERCURY,  243 

the  alkali  metals  dissolving  with  the  production  of  a  flash  of  light. 
Amalgams  are  also  obtained  when  mercm-y  is  added  to  a  metallic 
salt  solution  or  a  metal  placed  in  a  mercuric  nitrate  solution.  The 
amalgams  richest  in  mercury  are  liquid,  while  those  poor  in  mercury 
are  solid  and  often  crystalline,  many  retaining  mercury  even  when 
heated  to  450°. 

Tin  amalgam  is  used  in  the  preparation  of  mirrors;  tin-zinc  amal- 
gam, for  the  f rictional-electric  machine;  cadmium,  platinum,  or  copper 
amalgams,  as  filling  for  teeth.  Anmionium  amalgam,  see  p.  216. 
The  amalgams  of  the  alkali  metals,  of  aluminium  or  magnesium 
evolve  a  constant  current  of  H  with  water  and  hence  are  used  as 
reducing  agents. 

6.  Mercurous  Compounds. 

Mercurous  oxide,  mercury  suboxide,  HggO,  is  obtained  as  a  brownish- 
black  powder  when  a  mercurous  salt  solution  is  treated  with  caustic 
alkali :  2HgCl  +  2K0H  =  Hg^O  +  2KC1  +  H^O.  It  decomposes  in  the  light 
into  HgO  +  Hg. 

Black  wash  is  prepared  by  mixing  calomel  with  lime-water  and  con- 
sists, therefore,  of  finely  divided  mercurous  oxide  suspended  in  lime-water 

Mercurous  hydroxide,  Hg(OH),  is  not  known,  as  it  decomposes  into 
water  and  mercurous  oxide  the  moment  it  is  produced  from  mercurous 
salts. 

Mercurous  sulphide,  HggS,  is  precipitated  from  mercurous  salt  solu- 
tions by  HoS  as  a  black  powder  which  quickly  decomposes  into  mercuric 
sulphide  and  mercury:  2HgN03  +  H2S=Hg2S  +  2HN03;  Hg2S=HgS+Hg. 

Mercurous  Chloride,  Calomel,  Mercury  Sub-  or  Protochloride,HgCl. 
Preparation.  1.  By  treating  a  mercurous  nitrate  solution  with 
hydrochloric  acid  or  a  solution  of  a  chloride  we  obtain  mercurous 
chloride  as  a  pure,  white  amorphous  precipitate:  HgNOg+HCl- 
HgCl+HNO,. 

2.  By  the  sublimation  of  mercuric  chloride  with  mercury :  HgClj-f- 
Hg  =  2HgCl.  The  calomel  is  obtained  by  this  method  as  a  radiated 
crystalline  yellowish-white  mass  which  when  rubbed  forms  a  yellowish 
powder,  and  when  scratched  gives  a  yellow  mark. 

If  in  the  sublimation  the  mercurous  chloride  vapors  are  quickly  cooled 
by  passing  them  into  a  cool  chamber  or  by  condensing  them  by  means  of 
steam,  we  obtain  a  very  fine  mercurous  chloride  which  appears  as  a  pure 
white  microcrystalline  powder. 

3.  By  reducing  a  warm  solution  of  mercuric  chloride  by  sulphur  dioxide 
we  obtain  a  white  crystalline  precipitate  of  mercurous  chloride: 

2HgCl2  +  SO2  +  2H2O = 2HgCl  +  2HC1  +  H^SO,. 


244  INORGANIC  CHEMISTRY. 

Properties.  Mercurous  chloride  is  insoluble  in  water,  alcohol, 
and  dilute  acids,  but  soluble  in  concentrated  acids,  forming  mercuric 
salts.  On  boihng  with  hydrochloric  acid  or  with  solutions  of  chlorides 
of  the  alkali  group  it  is  transformed  into  the  very  poisonous  mercuric 
chloride  and  mercury  separates  out.  On  heating  it  vaporizes  without 
melting. 

By  caustic  alkalies  it  is  converted  into  the  brownish-black  mercurous 
oxide,  and  when  treated  with  ammonia  it  becomes  black  (hence  its  name, 
i<aA.6'5,  beautiful,  jiid/ias,  black),  when  probably 

Mercurous  ammonium  chloride,  NHgCHgJCl,  is  formed: 
2HgCl  +  2NH3=  NH2(Hg2)Cl  +  NH^Cl. 

Mercurous  Iodide,  Hgl.  Preparation.  By  treating  a  dilute 
mercurous  nitrate  solution  with  potassium  iodide  solution,  or  ordi- 
narily by  rubbing  mercury  and  iodine  together  in  atomic  proportions. 

Properties.  Amorphous  greenish-yellow  powder  insoluble  in 
water  and  alcohol  and  gradually  decomposing  in  the  light  into  mer- 
curic iodide  and  mercury,  and  quickly  on  heating:  2HgI  =HgI^-|-Hg. 
An  aqueous  solution  of  potassium  iodide  produces  the  same  change. 

It  is  produced  as  crystalline  yellow  leaves  by  heating  mercurous 
nitrate  solution  with  iodine:  2HgN03  +  I=  Hgl +Hg(N03)2.  On  heating 
the  amorphous  and  crystalline  salt  it  sublimes  into  red,  needle-shaped 
crystals  which  quickly  turn  yellow  again. 

Mercurous  sulphate,  Hg2S04  (preparation,  p.  242),  precipitates  also 
from  concentrated  mercurous  nitrate  solutions  by  the  addition  of  HgSO^ 
as  colorless  crystals  which  are  difficultly  soluble  and  which  decompose  on 
heating  into  Hg2  +  S02  +  02,  and  with  cold  water  form  greenish-yellow 
insoluble  basic  mercurous  sulphate,  Hg20  +  Hg2S04  +  H20. 

Mercurous  nitrate,  HgNOg,  is  produced  by  the  action  of  cold  or  slightly 
warmed  nitric  acid  upon  an  excess  of  mercury  (process,  p.  242).  It  forms 
colorless  monoclinic  crystals,  HgNOg  +  HoO,  which  are  soluble  in  a  small 
amount  of  warm  water,  but  which  decompose  on  the  addition  of  more  water 
into  the  soluble  acid  salt  and  into  the  pale-yellow  insoluble  basic  salt, 
HgOH.HgNOg.  If  the  aqueous  solution  is  treated  with  ammonia,  a  black 
precipitate  of 

Mercurous  ammonium  nitrate,  NH2(Hg2)N03,  mixed  with  mercurous 
oxide  is  obtained.     This  precipitate  is  used  in  pharmacy. 

c.  Mercuric  Compounds. 
Mercuric  Oxide,  Mercury  Oxide,  HgO.  Preparation.  1.  Mer- 
cury is  heated  nearly  to  its  boiling-point  for  a  long  time  in  the  air.  On 
a  large  scale  a  mixture  of  mercuric  nitrate  and  mercury  are  heated 
until  no  more  red  vapors  of  nitrogen  oxides  are  evolved :  Hg(N03)2+ 
3Hg  =  4HgO-f-2NO.  Thus  produced  it  forms  a  red  crystalUne 
powder  (red  precipitate)  which  does  not  combine  with  oxahc  acid. 


J 


MERCURY,  245 

2.  If  a  mercuric  salt  solution  is  treated  with  caustic  alkali,  an 
orange-yellow  amorphous  powder  is  obtained  which  when  shaken  with 
an  oxahc  acid  solution  forms  white  mercuric  oxalate :  HgCl2+  2K0PI  = 
HgO+2KCl+H20. 

Properties.  It  is  insoluble  in  water,  readily  soluble  in  acids. 
When  carefully  heated  it  becomes  red,  then  black,  and  on  coohng 
red  again.  At  a  red  heat  it  decomposes  into  its  elements,  and  with 
ammonia  it  combines,  forming  white  2HgO+NH3,  which  explodes 
on  heating. 

Yellow  wash  is  prepared  by  mixing  mercuric  chloride  with  lime-water 
and  hence  consists  of  finely  divided  mercuric  oxide  suspended  in  lime- 
water. 

Mercuric  hydroxide,  Hg(0H)2,  is  not  known  because  as  soon  as  it  is 
formed  it  decomposes  into  mercuric  oxide  and  water: 

-      HgCl,  +  2KOH=Hg(OH)2  +  2KCl;  Hg(OH)2=HgO  +  HA 

Mercuric  Sulphide,  HgS.  Occurrence.  As  cinnabar  in  dark-red 
crystals  or  masses. 

Preparation.  1.  Black  microcrystalhne  mercuric  sulphide  can 
be  obtained  by  passing  HjS  into  a  mercuric  salt  solution,  HgCl2+ 
H2S  =  HgS+2HCl,  or  as  a  black  powder  by  the  continuous  rubbing 
of  quicksilver  and  moist  sulphur  together. 

2.  Red  crystalline  mercuric  sulphide  is  produced  by  prolonged 
heating  of  black  HgS  with  alkah  sulphides  and  water,  forming  a 
beautiful  scarlet-red  powder.  On  the  subhmation  of  black  HgS 
in  the  presence  of  air  a  dark-red  crystalline  mass  is  obtained  which 
is  similar  to  natural  cinnabar  and  which  on  being  ground  gives  a 
scarlet-red  non-poisonous  powder  (vermilion,  Chinese  red). 

Properties.  Both  modifications  are  insoluble  in  water,  alcohol, 
hydrochloric  or  nitric  acids,  but  readily  soluble  in  aqua  regia,  forming 
mercuric  chloride.  On  heating  in  the  air  they  decompose  into  sul- 
phur dioxide  and  mercury  (p.  242). 

Mercuric  Chloride,  Corrosive  Sublimate,  Mercury  Bichloride, 
HgClj.  Preparation.  1.  On  heating  mercury  in  chlorine  gas  or  by 
dissolving  mercury  in  aqua  regia  and  evaporating  to  crystaUiza- 
tion. 

2.  By  heating  sodium  chloride  with  mercuric  sulphate,  when  the 
mercuric  chloride  sublimes,  while  the  sodium  sulphate  remains: 
2NaCl+  HgSO^  =  Na^SO^^-  HgCl^. 

Properties.    Sublimed   it   forms   a   white   crystalline  mass,  and 


246  INORGANIC  CHEMISTRY, 

when  ground  a  white  powder  (mercurous  chloride  gives  a  yellowish 
powder).  It  is  soluble  in  16  parts  of  water,  3  parts  of  alcohol,  14 
parts  of  ether,  and  crystallizes  from  these  solutions  in  rhombic  prisms. 
Reducing  bodies  (SO2,  p.  243,  SnCl^,  p.  258)  convert  it  into  mercurous 
chloride  and  then  into  mercury.  With  alkaU  chlorides  it  forms 
stable  neutral  double  salts,  HgCl2+2KCl+H20,  which  are  soluble 
in  water.  It  is  very  poisonous  and  prevents  putrefaction  of  organic 
bodies  by  forming  insoluble  compounds  with  the  proteids  thereof. 
As  mercuric  chloride  is  precipitated  by  proteid  solutions,  these  bodies 
are  used  as  antidotes  in  mercurial  poisoning. 

Tablets  composed  of  equal  parts  HgClg  and  NaCl  are  used  in  surgery. 

Mercuric  ammonium  chloride,  NHjHgCl  (NH4CI  in  which  2  H 
atoms  are  replaced  by  the  divalent  Hg  atom),  is  formed  by  precipi- 
tating mercuric  chloride  solution  with  an  excess  of  ammonia  solu- 
tion: HgCl2+2NH3=NH,Cl+NH2HgCl.  It  forms  a  white  mass 
or  an  amorphous  powder  which  is  insoluble  in  water  and  alcohol,  but 
readily  soluble  in  acids. 

On  heating  it  volatilizes  without  melting,  but  decomposes;  hence  it  is 
called  also  white  infusible  precipitate,  in  distinction  from  the  fusible  pre- 
cipitate ClHgN-Hg-NHgCl. 

Mercuric  Iodide,  Biniodide  of  Mercury,  Red  Iodide,  Hgl.  Prepara- 
tion. 1.  In  a  manner  analogous  to  that  of  mercurous  iodide  by  rub- 
bing atomic  amounts  of  mercury  and  iodine, 

2.  Ordinarily  by  precipitating  mercuric  chloride  with  a  potassium 
iodide  solution:  HgCl2+2KI  =Hgl2+2KCl. 

Properties.  An  amorphous  powder  which  at  first  is  yellow,  then 
turns  a  beautiful  red;  it  is  insoluble  in  water,  readily  soluble  in 
alcohol,  potassium  iodide,  and  mercuric  chloride.  It  crystaUizes 
from  alcoholic  solutions  as  red  quadrioctahedra. 

On  sublimation  or  on  heating  to  126°  it  is  converted  into  a  yellow 
rhombic  modification  which  quickly,  especially  in  the  light,  is  transformed 
again  into  the  red  modification. 

Nessler's  reagent  is  a  solution  of  mercuric  iodide  in  potassium  iodide 
made  alkaline  with  caustic  alkali.  It  is  used  in  the  detection  of  the  small- 
est traces  of  ammonia  or  its  salts,  as  it  gives  a  brown  precipitate  or  colora- 
tion of  dimercuric  ammonium  iodide,  NHgJ  +  H^O. 

Mercuric  sulphate,  HgSO^  (preparation,  p.  242),  forms  colorless  crystals 
which  by  boiling  water  are  converted  into  a  basic  mercuric  sulphate, 
HgS04  +  2HgO.  With  alkali  sulphates  it  forms  double  salts,  RgSO^^ 
KgSO^-f-GHjO,  which  are  isomorphous  with  those  of  the  magnesiimi 
group. 


GROUP  OF  EARTHY  METALS.  247 

Mercuric  nitrate,  Hg(N03)2,  is  obtained  by  dissolving  mercury  in  an 
excess  of  hot  nitric  acid  (process,  p.  242).  It  forms  colorless  crystals, 
,  2Hg(N03)2  +  H20,  which  with  large  quantities  of  water  form  a  white  basic 
salt,  Hg(N03)2  +  2HgO+H20.  It  is  used  in  the  estimation  of  urea, 
according  to  Liebig-Pfliiger,  as  well  as  a  reagent  for  proteids  (Millon's 
reagent). 

d.  Detection  of  Mercury  Co7npounds. 

1.  If  they  are  heated  in  a  glass  tube  with  Na2C03,  a  gray  subli- 
mate of  metaUic  mercury  deposits  on  the  cold  part  of  the  tube. 

2.  When  placed  on  metallic  copper  mercury  deposits  as  a  gray 
coating  which  becomes  bright  on  being  rubbed,  and  which  disappears 
on  heating. 

3.  Sulphuretted  hydrogen  precipitates  black  mercuric  sulphide 
from  solutions  containing  mercury.  This  precipitate  is  character- 
ized from  all  other  sulphides  by  being  insoluble  in  hot  nitric  acid. 

4.  Stannous  chloride  precipitates  white  mercurous  chloride  or 
black  (finely  divided)  mercury  (p.  258)  from  mercurial  solutions. 

5.  Mercurous  compounds  turn  black  with  caustic  alkalies,  black 
with  ammonia  (p.  244),  yellowish  green  with  potassium  iodide,  and 
white  with  hydrochloric  acid. 

6.  Mercuric  compounds  become  yellow  with  caustic  alkalies, 
white  with  ammonia  (p.  246),  red  with  potassium  iodide,  and  are  not 
changed  with  hydrochloric  acid. 

GROUP  OF  EARTHY  METALS. 

ALUMINIUM.      GALLIUM.      INDIUM.      THALLIUM. 

Scandium.     Yttrium.     Lanthanum.     Cerium. 

Praseodymium.     Neodymium.     Samarium.     Gadolinium. 

Erbium.     Thulium.     Ytterbium. 

Decipium.     Dysprosium.     Holmium.     Philippium.     Terbium. 

The  earthy  metals  occur  only  combined  in  nature  and,  with  the  excep- 
tion of  gallium,  thallium,  and  cerium,. exist  as  trivalent  elements. 

The  preparation  of  pure  earthy  metals  is  very  difficult,  as  in  their 
chemical  behavior  they  are  extremely  similar.  They  are  especially  charac- 
terized by  their  spectrum,  and  many  of  their  oxides  (especially  cerium 
dioxide,  CeOg,  see  thorium,  p.  263)  emit  an  intense  white  light  on  being 
heated  in  a  non-luminous  flame. 

Their  salts  and  their  solution  are  partly  colored,  and  each  metal  gives 
a  characteristic  absorption  spectrum. 

Thev  differ  from  the  alkali  and  alkaline-earth  metals  in  that  their 
hydroxides  are  precipitated  by  ammonia  and  that  they  decompose  water 
onlv  at  high  temperatures.  They  are  not,  with  the  exception  of  indium, 
thallium,  and  gallium,  in  common  with  these  two  groups,  precipitated 
by  H2S,  as  their  sulphides  are  soluble  or  unstable. 


248  INORGANIC  CHEMISTRY. 

Aluminium,  gallium,  indium  form  soluble  salts  with  oxalic  acid.  Their 
sulphates  form  double  salts  having  the  formula  MK (804)2,  called  alums, 
with  the  alkali  sulphates  and  ammonium  sulphate.  These  are  soluble* 
in  water  and  form  octahedral  crystals. 

Thallium  shows  a  different  behavior  (p.  255).  The  elements  of  the 
second  and  following  series  are  called  rare  earthy  metals  and  occur  in 
certain  rare  minerals  found  in  Sweden,  Norway,  and  America,  such  as 
cerite,  euxenite,  gadolinite,  orthite,  seschynite,  fergusonite,  monazite,  poly- 
crase,  yttrotantalite,  samarskite,  and  especially  in  monazite  sand. 

They  form  difficultly  soluble  or  insoluble  salts  with  oxahc  acid,  and 
their  soluble  sulphates  yield  double  salts  with  potassium  sulphate,  having 
the  formula  MK3(S04)3,  of  which  those  of  scandium,  samarium,  thulium, 
decipium,  erbium,  holmium,  philippium,  and  terbium  are  insoluble  in  a 
saturated  potassium  sulphate  solution.  The  elements  of  the  last  series 
consist  perhaps  of  a  mixture  of  still  imknown  elements. 

I.  Aluminium. 

Atomic  weight  27.1  =  A1. 

Occurrence.  Only  combined.  To  a  slight  extent  as  aluminium 
oxide,  sulphate,  and  hydroxide  (which  see),  but  in  large  quantities 
as  aluminium  siHcate;  thus  feldspars,  micas,  zeohtes,  chlorites,  and 
many  other  minerals  are  compounds  of  aluminium  sihcate  (which 
see)  with  other  metallic  silicates,  forming  granite,  porphyry,  gneiss, 
mica  schist,  slate,  clay,  the  chief  constituents  of  the  earth's 
crust.  Andalusite,  obsidian  (pumice-stone),  garnets,  lapis-lazuli,  to- 
paz, tourmalin,  etc.,  consist  chiefly  of  aluminium  silicates.  Cryolite, 
AlFg+SNaF,  forms  enormous  deposits  in  Greenland.  Despite  this 
wide  distribution  of  aluminium  compounds  they  occur  in  only  a  few 
plants  and  not  at  all  in  the  animal  kingdom. 

Preparation.  1.  By  heating  aluminium  chloride  or  cryohte  with 
sodium :   AICI3+  3Na  =  A1+  3NaCl. 

2.  By  the  electrolysis  of  aluminium  oxide  (alumina)  which  is 
dissolved  in  fused  cryolite. 

Properties.  Silver-white  ductile  metal  of  a  specific  gravity  of  2.6 
and  melting  at  700°  without  oxidation.  On  heating  higher  it  burns 
without  volatilizing,  producing  aluminium  oxide.  When  finely 
powdered  or  in  thin  leaves  it  burns  readily  in  the  air  with  a  bright 
light  and  decomposes  boiling  water  with  the  generation  of  hydrogen. 
When  compact  it  does  not  decompose  water  even  at  a  white  heat; 
at  its  melting-point  it  is  an  energetic  reducing  agent;  therefore  it  is 
used  in  the  obtainment  of  metals  which  can  otherwise  only  be  re- 
duced from  their  oxides  in  the  electric  furnace. 


ALUMINIUM.  249 

The  lieat  of  reaction  set  free  in  its  union  with  oxygen  is  used  in  order  to 
obtain  temperatures  up  to  3000°  (by  the  compound  called  thermite,  which 
is  a  mixture  of  powdered  aluminium  with  iron  oxide),  and  is  also  used  in 
welding  and  melting  processes,  as  well  as  in  reduction  processes  which  do 
not  take  place  at  lower  temperatures.  This  reduction  is  brought  about 
according  to  Goldschmidt's  method,  which  consists  in  mixing  the  oxide 
of  the  metal  to  be  obtained  with  aluminium  powder,  and  to  ignite  this 
mixture  (reduction  mass)  by  means  of  a  mixture  of  aluminium  and  BaOj 
(ignition  mass).  By  this  method  numerous  metals  which  were  formerly 
fused  and  reduced  with  difhculty  are  now  obtained  in  a  very  pure  and 
fused  state. 

Aluminium  dissolves  readily  in  hydrochloric  acid  or  caustic 
alkali  with  the  development  of  hydrogen:  A1+K0H+H20  = 
KAIO2+3H.  It  dissolves  in  hot  sulphuric  acid  with  the  generation 
of  SO2,  and  it  is  only  slowly  acted  upon  by  dilute  sulphuric  acid  and 
nitric  acid,  as  it  becomes  covered  with  a  thin  layer  of  AljOg  besides 
H  or  NO.  Under  the  air-pump  receiver  it  dissolves  readily  in  all 
acids,  as  the  protective  layer  of  gases  is  removed.  On  account  of  its 
lightness  and  its  stability  in  the  air  it  is  very  extensively  used  in  the 
preparation  of  many  useful  objects. 

a.  Alloys  of  Aluminium. 

The  copper  alloy,  aluminium  bronze,  is  characterized  by  being 
very  hard  and  stable  and  by  its  golden  color. 

Magnalium  is  an  alloy  with  magnesium  and  has  properties  similar 
to  brass. 

Partinium  is  an  alloy  Avith  tungsten  and  is  much  more  stable 
than  aluminium. 

h.  Compounds  of  Aluminium. 

Aluminium  Oxide,  Alumina,  AI2O3.  Occurrence.  In  colorless, 
transparent  hexagonal  crystals  it  is  corundum ;  colored  red  with  chro- 
mium it  is  called  ruby;  colored  blue  by  cobalt  it  is  known  as  sapphire; 
and  the  bluish-gray  crystalUne  masses  are  called  emery. 

Preparation.  Amorphous  by  heating  aluminium  hydroxide; 
crystalline  by  heating  boron  trioxide  with  aluminium  fluoride, 
2A1F3+B203  =  A1203+ 2BF3;  also  by  passing  chlorine  over  red-hot 
sodium  aluminate,  2NaA102+2Cl  =  Al203-f  2NaCl+0,  as  well  as  in 
Goldschmidt's  process  (see  above). 

Properties.  Next  to  diamond  and  boron  crystalline  alumina  is 
the  hardest  of  all  bodies  and  forms  colorless  hexagonal  prisms. 
Amorphous  alumina  is  a  white  odorless  and  tasteless  powder  which 


250  INORGANIC  CHEMISTRY, 

melts  in  the  oxyhydrogen  flame  and  then  forms  a  very  hard  mass 
similar  to  burnt  clay.  When  calcined  it  is,  like  crystalline  alumina, 
insoluble  in  acids  and  can  only  be  converted  into  a  soluble  com- 
pound by  fusion  with  caustic  potash  or  potassium  bisulphate  (p.  206). 

Aluminium  Hydroxide,  A1(0H)3.  Occurrence.  It  occurs  as  hy- 
drargilUte,  combined  with  A1K(S04)2  ^^  alum-stone  (p.  251) ;  as  bauxite, 
Al20(OH)4,  mixed  with  iron  oxide;  and  as  AIO(OPI),  diaspore. 

Preparation.  1.  A1(0H)3  is  precipitated  from  aluminium  salt 
solutions  by  ammonia.  Sodiiun  carbonate  also  precipitates  A1(0H)3 
from  aluminium  salt  solutions,  as  the  aluminium  carbonate  first 
formed  decomposes  immediately: 

2AlCl3+3Na2C03  =  6NaCl+ Al2(C03)3; 
AI2  (003)3+ SHp  =2A1(0H)3+3C02. 

2.  On  a  large  scale  from  cryolite  or  bauxite. 

Cryolite  is  heated  with  limestone,  when  soluble  sodium  aluminate  and 
insoluble  calcium  fluoride  are  formed:  AlF3.NaF  +  3CaC03=Na3A103  + 
BCaFg  +  SCOa.  Bauxite  is  heated  with  sodium  carbonate:  AX^OiOW)^-^- 
3NaC03=  2Na3A103  +  2H2O  +  300^.  The  NagAlOg  is  dissolved  in  water,  and 
the  carbon  dioxide  generated  passed  into  the  solution,  which  forms  sodium 
carbonate  and  precipitates  aluminium  hydroxide:  2Na3A103  +  BCOg + 
3H20  =  3Na2C03  +  2Al(OH)3.  On  treatment  with  water  Al'(0H)3  remains 
undissolved  and  the  sodium  carbonate  is  obtained  from  the  aqueous  solu- 
tion by  evaporation. 

3.  As  a  by-product  in  the  preparation  of  potassium  alum  from  alum- 
stone  (p.  252). 

Properties.  White  gelatinous  precipitate  which  when  dry  forms 
a  white  powder  and  which  is  insoluble  in  water;  still  by  dialysis  its 
solution  in  aluminium  chloride  and  also  in  water  can  be  obtained. 
It  is  soluble  in  acids  as  well  as  in  caustic  alkahes:  A1(0H)3+K0H  = 
KAIO2+2H2O.  It  acts  like  other  weak  bases,  being  an  acid  towards 
stronger  bases,  forming  salts  that  are  called  aluminates  (see  below). 
On  careful  warming  the  A1(0H)3  can  be  transformed  into  the  above- 
mentioned  hydrate,  Al,0(OH),  =  2Al(OH)3-H20  and  AIO(OH)  = 
Al(OH)3-H26. 

When  freshly  precipitated  it  has  the  property  of  carrying  down 
with  it  dissolved  inorganic  and  organic  bodies.  This  is  made  use  of 
in  the  clarification  of  many  hquids,  and  in  the  precipitation  of  organic 
pigments  from  their  solution  (preparation  of  lake  colors),  as  well 
as  in  dyeing,  where  it  is  employed  as  a  mordant  (fixing  of  colors  in 
plant-fibres),  whereby   the  A1(0H)3  is   deposited  directly  upon  the 


ALUMINIUM.  251 

tissues  by  dipping  first  in  aluminium  acetate    or  sodium  aluminate 
and  then  exposing  to  steam,  when  A1(0H)2  is  formed. 

Aluminates.  On  treating  solutions  of  aluminium  hydroxide  in  alkali 
hydroxides  with  alcohol  a  precipitate  having  the  composition  KAIO2  or 
NaAlOg  is  obtained.  The  acid-forming  aluminium  hydrate,  HAlOg,  corre- 
sponding thereto  occurs  as  diaspore,  Mg(A102)2  as  spinel,  Be(A102)2  as 
chrysoberyl,  Zn(A102)2  as  gahnite,  and  Fe(A102)2  as  pleonaste. 

Sodium  aluminate  is  prepared  on  a  large  scale  (see  Aluminium  Hydrox- 
ide, p.  250). 

The  aluminates  soluble  in  water  are  immediately  decomposed  by 
carbon  dioxide  into  aluminium  hydroxide. 

Aluminium  chloride,  AICI3,  is  obtained  by  dissolving  aluminium  hydrox- 
ide in  hydrochloric  acid  and  evaporating.  P.  forms  white  deliquescent 
crystals,  AICI3  +  6H2O,  which  decompose  on  heating:  2A1C13+3H20= 
AI2O3  +  6HCI.  With  metallic  chlorides  it  forms  double  salts  whose  solu- 
tion can  be  evaporated  without  decomposition:  AICI3  +  3KCI.  On  a 
large  scale  the  anhydrous  aluminium  chloride  can  be  prepared  by  strongly 
heating  a  mixture  of  aluminium  oxide  and  carbon  in  chlorine  gas.  This 
forms  a  white  dehquescent  crystalline  mass:  Al203  +  3C  +  6C1=2A1C13+ 
SCO. 

Aluminium  fluoride,  AIF3,  occurs  in  cryolite  (p.  248),  and  with  9H2O 
forms  colorless  crystals  which  are  soluble  in  hot  water. 

Aluminium  sulphide,  AI2S3,  is  obtained  by  heating  aluminium  with 
sulphur,  which  gives  a  yellow  mass  decomposable  by  water. 

Aluminium  Sulphate,  AljCSOJg-f- I8H2O,  also  called  concen- 
trated alum,  occurs  as  alunogen,  feather-alum,  aluminite,  websterite, 
as  well  as  alum-stone  (p.  252). 

Preparation.  1.  By  dissolving  aluminium  hydroxide  (obtained 
on  a  large  scale  from  bauxite  or  cryolite,  p.  250)  in  sulphuric  acid 
and  then  evaporating. 

2.  Alum-slate  or  alum-earth  (aluminium  silicate  which  contains  car- 
bon and  iron  pyrites)  or  ordinary  clay  (p.  252)  are  transformed  into 
aluminium  sulphate  by  means  of  sulphuric  acid,  then  lixiviated  with 
water,  which  leaves  the  silicic  acid  behind.  The  solution  is  evaporated 
when  most  of  the  difficultly  soluble  iron  sulphate  first  crystallizes  out  and 
then  the  aluminium  sulphate. 

Properties.  Aluminium  sulphate  forms  colorless  monoclinic 
crystals  or  crystalline  masses  which  are  readily  soluble  and  have 
an  acid  reaction. 

If  a  solution  of  aluminum  sulphate  is  treated  with  a  solution  of 
a  sulphate  of  the  alkaU  metals,  of  ammonium,  silver,  or  thallium, 
we  obtain  on  evaporation  the  double  salts,  which  crystallize  in  regu- 
lar octahedra,  are  much  less  soluble  in  water  than  the  aluminium 
sulphate,  and  have   the   composition   MA1(S04)2+ 12H.0,  where  M 


252  INORGANIC  CHEMISTRY. 

may  be  K,  Na,  Cs,  Rb,  Ag,  Tl,  or  NH4,  or  an  organic  derivative  of 
NH4.  These 'double  salts  are  called  alums  and,  according  to  the  mono- 
valent metal  they  contain,  are  designated  potassium  alum,  sodium 
alum,  ammoniimi  alum,  silver  alum,  etc. 

Ferric,  manganic,  and  chromic  sulphates  and  those  of  indium  and 
gallium  also  form  double  salts  with  the  sulphates  of  the  monovalent 
metals.  These  double  salts  have  the  same  shape  and  composition, 
hence  the  term  alums  is  also  applied  to  these  double  salts. 

Alums  are  hence  isomorphous  double  salts  having  the  formula 
I  III  I 

MM(S04)2+12H20,  where  M  may  be  K,  Na,  Cs,  Rb,  Ag,Tl,orNH4; 

III 
and  M  may  be  Al,  Fe,  Mn,  Cr,  In,  or  Ga: 

FeNaCSOJj  +  I2H2O,  Sodium  iron  alum. 
CrNH4(S04)jj+  I2H2O,  Ammonium  chromium  alum. 
MnK.  (804)2   +  I2H2O,  Potassium  manganese  alum. 

Ammonium  alum,  A1(NH4)  (804)2+ I2H2O,  and 

Potassium  alum,  alum,  A1K(804)2+12H20,  are  the  most  import- 
ant of  these  double  salts  and  are  at  the  present  time  more  and  more 
replaced  in  technology  by  aluminium  sulphate  or  sodium  aluminate 
(preparation,  see  Alumiunium  Hydroxide,  p.  250). 

Preparation.  1.  From  alum-stone  (alunite),  A1K(S04)2  +  2A1(0H)3,  by 
heating  and  then  extraction  with  water,  when  the  aluminium  hydroxide 
remains  undissolved  and  the  potassium  alum  is  obtained  from  the  solution 
by  evaporation  and  crystallization. 

2.  On  a  large  scale  from  the  aluminium  sulphate  obtained  from  alum 
slate,  bauxite,  or  cryolite,  by  treating  its  solution  with  potassium  or 
ammonium  sulphate  and  evaporating  to  crystallization. 

Properties.  Large  colorless  octahedral  crystals  soluble  in  10 
parts  water,  giving  an  acid  reaction  to  the  solution,  and  which  on 
heating  fuse  in  their  water  of  crystallization,  and  on  further  heating 
are  converted  into  anhydrous  white  porous  alum  (burnt  alum). 
From  its  hot  solution  in  water  treated  vnth.  some  alkali  carbonate 
alum  crystaUizes  on  evaporation  in  cubes  as  so-called  neutral  or 
cubical  alum,  which  is  soluble  in  water  with  neutral  reaction. 

Aluminium  Silicates.  Occurrence.  As  constituent  of  the  most  im- 
portant rocks  of  the  earth  (see  Aluminium,  p.  248),  also  in  the  impure 
form  as  alum-slate,  alum-stone,  and  as  ordinary  clay,  and  in  the  pure 
state  as  white  clay  (kaohn,  porcelain  earth,  argilla):  H2Al2(8i04)2+ 
HjO.     Ordinary  clay  forms  immense  layers  and  is  produced  by  the 


ALUMINIUM.  253 

weathering  of  feldspathic  rocks,  and  is  a  mixture  of  white  clay  with 

other  sihcates,  calcium  carbonate,  ferric  hydroxide,  etc. 

By  the  influence  of  water  and  carbon  dioxide  the  feldspars,  MAlaCSiOJg 
or  MAlgSigO^g  (M=Na2,  K^,  Mg,  Ca),  are  so  decomposed  that  the  alkaline 
earths  are  converted  into  soluble  bicarbonates  and  the  alkalies  into  solu- 
ble silicates  (which  are  further  decomposed  into  carbonate  and  free  silicic 
acid),  while  the  insoluble  aluminium  silicate  remains  as  clay: 

K^Al^SieOn  +  H^O = K^Si.Og  +  H^Al^CSiO^)^; 

CaAl2(SiO,)2  +  2H2O  +  200^=  CaH^CCOg)^  +  H^Al^CSiO  J^- 

Ochre,  Sienna  earth,  Naples  red,  are  natural  mixtures  of  clay  with 
considerable  ferric  oxide.  Loam  is  a  mixture  of  clay,  sand,  and  ferric 
oxide,  while  marl  is  a  mixture  with  considerable  calcium  carbonate. 

Properties.  Aluminium  ^ilicates  are  partly  decomposable  by 
acids,  while  some  must  first  be  decomposed  (p.  197).  The  clays  are 
gray,  brown,  or  yellow  in  color  and  absorb  water  and  then  form 
plastic  masses  which  shrink  on  heating,  when  their  hardness  increases, 
so  that  they  yield  sparks  when  struck  with  steel.  Clays  lose  the 
property  of  being  plastic  with  water  after  heating  and  become 
porous  and  allow  water  to  pass  through.  The  purer  the  clay  the 
more  infusible  it  is,  and  mixtures  of  clay  and  lime,  iron  oxide,  lead 
oxide,  alkali  salts  are  more  or  less  fusible  and  impervious  to  water. 

Porcelain  and  earthenware  consist  of  burnt  clay  to  which  have 
been  added  bodies  (feldspar,  for  example)  which  accelerate  fusion,  or 
the  clay  may  be  covered  with  a  thin  layer  of  readily  fusible  silicates 
which  produce  an  impervious  covering  (glaze). 

According  to  the  purity  of  the  clay  and  the  temperature  used  in  its 
preparation  we  differentiate  between: 

a.  Compact  earthenware  with  glass-like  fracture  and  more  or  less 
transparent.  Although  these  are  impervious  to  water  by  the  flux  added 
before  burning,  they  are  still  covered  with  a  glaze  in  order  to  make  the 
rough  surface  smooth  and  polished.  Porcelain  is  white  and  transparent, 
while  earthenware  (stoneware)  is  white,  gray,  yellow,  or  brown,  and  non- 
transparent.     Ung;lazed  porcelain  is  called  bisque. 

6.  Porous  earthenware,  which  is  earthy  on  fracture  and  completely  non- 
transparent.  It  absorbs  water  and  sticks  to  the  tongue.  To  this  group 
belong  Fayence  ware,  crockery,  Majolica  ware,  Delft  ware,  ordinary 
pottery,  terra  cotta,  bricks,  Hessian  crucibles,  etc. 

Cement  (p.  220)  is  also  artificially  made  by  heating  clay  with  lime- 
stone and  is  a  calcium-aluminium  silicate. 

UUramnrine.  By  heating  a  mixture  of  porcelain  clay,  wood  charcoal, 
soda,  and  sulphur  in  the  absence  of  air,  we  obtain  green  ultramarine,  which 
forms  blue  ultramarine  on  heating  again  with  sulphur  in  the  air. 

Violet  and  red  ultramarine  are  produced  when  dry  hydrochloric  acid 
cas  and  air  are  passed  over  blue  ultramarine  at  150°. 


254  INORGANIC  CHEMISTRY. 

Dilute  acids  decolorize  ultramarine  with  the  setting  free  of  HjS,  sul- 
phur, and  gelatinous  silicic  acid.  It  probably  consists  of  sodium-aluminium 
silicate,  Na^AlgCSiOJa,  and  sodium  polysulphides. 

The  rare  blue  mineral  lapis-lazuli  has  perhaps  a  similar  composition. 

c.  Detection  of  Aluminium  Compounds. 

1.  When  moistened  with  a  cobaltous  salt  solution  and  heated  upon 
charcoal  in  the  blowpipe  flame  they  give  a  beautiful  blue  cobalt 
aluminate,  Co(A102)2  (Thenard's  blue,  cobalt  blue,  Leyden  blue,  and 
cobalt  ultramarine). 

2.  Ammonia  or  ammonium  sulphide  precipitates  aluminium 
hydroxide  from  its  solutions.  The  precipitate  is  insoluble  in  an 
excess  of  the  precipitant.  , 

3.  Caustic  alkalies  precipitate  aluminium  hydroxide,  which  is  soluble 
in  an  excess  of  the  precipitant. 

2.  QalHum. 

Atomic  weight  70=Ga. 

Occurs  only  combined  to  a  very  trivial  extent  in  certain  zinc  blendes 
as  gallium  sulphide,  GagSj.  It  is  obtained  by  the  electrolysis  of  its  sul- 
phate. It  is  a  hard  white  metal  having  a  specific  gravity  of  5.9  and 
fusing  at  30°,  volatile  at  about  900°,  and  stable  in  the  air. 

Gallium  compounds  do  not  give  any  color  to  the  colorless  flame.  On 
volatilization  by  the  electric  spark  a  spectrum  consisting  of  two  bright 
violet  lines  is  obtained. 

Sulphuretted  hydrogen  precipitates  white  gallium  sulphide,  GagSg, 
from  neutral  or  acetic  acid  solutions  of  gallium  only  in  the  presence  of 
other  precipitable  metallic  salts.  This  precipitate  is  soluble  in  mineral 
acids. 

3.  Indium. 

Atomic  weight  114=  In. 

Occurs  only  combined  to  a  very  slight  extent  in  many  zinc  blendes  as 
indium  sulphide,  lUgSg.  It  is  obtained  by  the  electrolysis  of  its  chloride 
as  a  soft  white  metal  which  is  stable  in  the  air,  has  a  specific  gravity  of 
7.4,  melts  at  176°,  and  vaporizes  at  about  1200°. 

Indium  compounds  give  a  bluish-violet  color  to  the  non-luminous 
flame,  and  the  spectrum  of  this  flame  consists  of  one  indigo-blue  line  (hence 
the  name  indium)  and  a  violet  line. 

Sulphuretted  hydrogen  precipitates  indium  from  its  solution  as  yellow 
indium  sulphide,  InjSg,  which  is  soluble  in  alkali  sulphides,  forming  sulpho 
salts,  and  insoluble  in  dilute  acids. 

4.  Thallium. 

Atomic  weight  204.1  =  T1. 

Thallium  occurs  as  a  univalent  and  as  a  trivalent  element.  According 
to  behavior  it  belongs  on  one  side  to  the  alkali  metals,  as  it  forms  when 


TIN.  255 

monovalent  a  soluble  hydroxide,  sulphate,  carbonate,  and  silicate,  also 
because  it  may  replace  the  alkali  metals  in  the  alums.  On  the  other  hand 
it  has  resemblances  to  lead  on  account  of  its  chloride  and  iodide,  which 
are  soluble  with  difficulty,  and  its  insoluble  sulphide,  and  also  on  account 
of  its  physical  properties. 

Thallium  occurs  only  in  combination,  up  to  17  per  cent,  in  crookesite, 
and  to  a  less  extent  in  many  sulphur  and  copper  ores,  in  certain  brines, 
especially  those  of  Nauheim,  and  in  sylvine  and  carnallite.  It  is  obtained 
by  the  electrolysis  of  its  chloride  as  a  very  soft  white  metal  which  melts 
at  290°  and  vaporizes  at  about  1600°,  has  a  specific  gravity  of  11.8,  and 
which  oxidizes  in  moist  air.  Thallium  compounds  give  a  beautiful  green 
color  to  the  colorless  flame,  and  the  spectrum  of  this  flame  consists  of  a 
single  bright-green  line  (^of  A/lo?,  green  bud).  It  is  precipitated  from  its 
solutions  by  ammonium  sulphide  as  black  thallium  sulphide,  TljS,  which 
is  soluble  in  dilute  acids. 

TIN  GROUP. 

Tin.     Germanium.     Lead. 

Titanium.     Zirconium.     Thorium. 

These  elements  with  carbon  and  silicon  form  a  group  (p.  185)  and 
exist  as  divalent  and  tetravalent  elements. 

Like  silicon  they  form  tetravalent  compounds,  such  as  volatile  tetra- 
chlorides, etc.,  and  their  tetrafluorides  combine  with  other  metallic  fluor- 
ides, forming  salts  corresponding  to  and  isomorphous  with  the  silico- 
fluorides;   thus  potassium  fluostannate,  KgSnFlfl. 

On  strongly  heating  they  burn  into  dioxides  (lead  into  PbO  or  PbgOJ 
which  are  acid  anhydrides. 

They  decompose  water  only  at  high  temperatures. 

Titanium,  zirconium,  and  thorium  compounds  are  not  precipitated 
from  their  neutral  or  acid  solution  by  H^S.  Zirconium  and  thorium  sul- 
phates give  double  salts  with  potassium  sulphate,  Zr(S04)2  +  K2S04  +  2H20, 
which  are  insoluble  in  saturated  solution  of  potassium  sulphate. 

I.  Tin  (Stannum). 

Atomic  weight  119  =  Sn. 

Occurrence.  Very  seldom  native,  to  a  slight  extent  as  SnSg,  but 
very  widely  distributed  as  cassiterite  or  tin-stone,  SnO.. 

Preparation.  Crushed  tin-stone  is  purified  from  foreign  materials 
by  means  of  water,  roasted,  and  then  heated  with  coal.  The  tin 
thus  obtained  contains  other  metals  and  is  therefore  slowly  heated 
again  to  fusion,  when  the  more  readily  fusible  tin  flows  off,  while 
the  more  infusible  metals  remain  behind  in  the  unmolten  state. 

Properties.  Silver-white,  soft,  malleable,  not  tough  metal  hav- 
ing a  specific  gravity  of  7.3.  At  200°  it  becomes  so  brittle  that  it  can 
be  pulverized,  at  231°  it  melts  and  is  covered  with  white  tin  oxide, 
and  at  about  1600°  it  is  volatile  and  burns,  when  air  is  supplied,  into 
tin  dioxide  (tin-ash).    It  is  stable  in  the  air,  hence  it  is  used  in  cover- 


256  INORGANIC  CHEMISTRY. 

ing  (tinning)  iron  and  copper  objects.  It  has  a  crystalline  fracture 
and  a  peculiar  crackling  sound  on  bending,  because  the  crystals  rub 
against  each  other  (cry  of  tin).  It  decomposes  water  at  a  red  heat, 
and  hydrochloric  acid  dissolves  it  with  the  liberation  of  hydrogen  and 
forms  stannous  chloride;  concentrated  sulphuric  acid  liberates  SO2  and 
forms  stannous  sulphate,  while  dilute  nitric  acid  evolves  NO,  forming 
stannous  nitrate.  Concentrated  nitric  acid  oxidizes  it  into  insoluble 
metastannic  acid,  while  anhydrous  nitric  acid  does  not  attack  tin  at 
all.  When  boiled  with  caustic  alkali  tin  dissolves  with  the  generation 
of  hydrogen  and  forms  alkali  stannate  (p.  257):  Sn+2KOH+H20  = 
K2Sn03+4H.  When  beaten  or  rolled  into  thin  leaves  it  is  called  tin- 
foil. 

Gray  tin,  an  allotropic  modification  having  a  specific  gravity  of  5.8,  is 
produced  by  the  action  of  low  temperatures  (-20°)  upon  pieces  of  tin 
which  gradually  change  into  gray  tin,  consisting  of  small  quadratic 
crystals  which  on  fusion  are  transformed  into  normal  tin.  Even  on  con- 
tact with  gray  tin  the  ordinary  white  tin  can  be  transformed  into  the  first 
variety  (tin-disease). 

Tin  occurs  divalent  in  the  stannous  compounds.  These  readily 
take  up  oxygen  and  are  therefore  strong  reducing  agents.  Stannous 
hydroxide  has  strong  basic  properties.  Tetravalent  tin  occurs  in 
the  stannic  compounds.  Stannic  hydroxide  behaves  sometimes  as 
a  weak  acid  and  again  as  a  weak  base. 

a.  Alloys  of  Tin. 

Cooking  utensils  made  of  tin  always  contain  some  lead,  and  the 
German  law  prescribes  that  such  utensils  must  not  contain  more  than 
10  per  cent,  of  lead.  Sheet  iron  covered  with  a  layer  of  tin  is  called 
tin-plate  or  sheet  tin.  Soft-solder  contains  30-60  per  cent.  lead. 
For  alloys  with  copper  see  p.  235;  with  antimony,  p.  178;  with  bis- 
muth, p.  264;  with  mercury,  p.  243. 

6.  Stannous  Compounds. 

Stannous  oxide,  SnO,  obtained  by  heating  stannous  hydroxide  in  the 
air,  is  a  stable  black  powder  insoluble  in  caustic  alkali  and  which  on 
heating  in  the  air  ignites  and  burns  into  stannic  oxide.  On  slowly  evap- 
orating a  solution  of  Sn(0H)2  in  caustic  alkali  it  is  obtained  as  dark-green 
crystals. 

Stannous  hydroxide,  Sn(0H)2,  is  produced  by  precipitating  a  stannous 
salt  with  caustic  alkali.  It  forms  a  white  precipitate  which  oxidizes  in 
the  air  into  stannic  hydroxide  and  dissolves  in  an  excess  of  the  caustic 
alkali.     Stannous  hydroxide  forms  salts  on  solution  in  acids. 

Stannous  chloride,  tin  protochloride,  SnClg,  is  ordinarily  prepared  by 
dissolving  tin  in  hydrochloric  acid  and  evaporating  the  solution.     The 


TIN.  257 

product  thus  obtained,  the  tin  salt  of  commerce,  SnCl2  +  2H20,  forms 
colorless  monoclinic  crystals  which  become  anhydrous  at  1C0°  and 
which  volatilize  without  decomposition  at  a  red  heat.  SnCl^  is  soluble  in 
little  water,  but  when  considerable  water  is  added  thereto  it  decomposes 
and  the  solution  becomes  cloudy,  due  to  the  formation  of  basic  stannous 
chloride,  Sn(OH.)Cl,  which  goes  into  solution  again  on  the  addition  of 
acids.  The  same  precipitate  is  obtained  when  the  clear  aqueous  solution 
is  allowed  to  stand  in  the  air:  3SnCl2  +  0  +  H,0  =  2Sn(OH)Cl  +  SnCl4. 
This  tendency  to  oxidize  is  so  strong  that  even  dry  stannous  chloride,  on 
exposure  to  the  air,  is  transformed  into  tin  oxychloride,  SnOClg,  and  hence 
is  an  energetic  reducing  agent.  In  regard  to  its  use  in  the  detection  of 
arsenic  see  p.  177. 

Stannous  sulphide,  SnS,  is  obtained  by  mixing  a  stannous  salt  solution 
with  HgS,  which  forms  an  amorphous  brownish-black  powder,  or  by  melt- 
ing tin  with  sulphur,  when  a  bluish-gray  crystalline  mass  is  produced.  It  is 
fusible,  insoluble  in  dilute  acids  and  alkali  monosulphides.  It  is  soluble  in 
alkali  polysulphides,  forming  alkali  sulphostannates :  SnS  4-  K2S2=  KgSnSy 

c.  Stannic  Compounds, 

Stannic  oxide,  tin  oxide,  stannic  anhydride,  SnOg,  occurs  as  tin- 
stone in  quadratic  crystals  or  compact  masses,  seldom  white,  but  generally 
colored.  It  is  produced  as  fine  needles  by  heating  tin  in  the  air,  or  as  an 
amorphous  white  or  yellowish  powder  by  heating  the  two  stannic  acids. 
This  powder  is  insoluble  in  water  and  in  acids,  but  soluble  in  alkali  hydrates, 
forming  stannates  (see  below). 

Stannic  hydroxide  has  the  formula  Sn(0H)4  or  SnO(OH)2  according 
to  the  method  of  drying.  Both  these  hydroxides  are  known  as  ortho-  and 
metastannic  acids. 

Orthostannic  acid  is  produced  on  boiling  a  watery  solution  of  stannic 
chloride  or  by  treating  this  solution  with  ammonia.  It  forms  a  gelatinous 
precipitate  wliich  when  dried  forms  a  vitreous  mass.  It  dissolves  readily 
in  acids,  forming  stannic  salts,  and  in  alkali  hydrates,  forming  stannic  acid 
salts  or  stannates;  thus,  Na^SnOg,  which,  on  evaporation  of  the  solution, 
may  be  obtained  as  crystals  and  from  which  acids  precipitate  ortho- 
stannic  acid,  which  is  soluble  in  an  excess  of  the  acid.  On  allow- 
ing orthostannic  acid  to  stand  under  water,  it  is  converted  into  meta- 
stannic acid  and  is  then  insoluble  in  acids.  Sodium  stannate,  NagSnOg-F 
3H2O,  is  used  in  cotton-printing  under  the  name  of  "  preparing-salt." 

Metastannic  acid  is  obtained  by  heating  tin  with  concentrated  nitric 
acid  as  a  white  powder  which  is  insoluble  in  acids.  With  alkali  hydrates 
it  forms  salts,  metastannates.  These  are  insoluble  in  the  alkali  hydrates, 
but,  on  the  contrary,  are  soluble  in  pure  water. 

Stannic  chloride,  tin  chloride,  SnCl^,  is  obtained  on  heating  tin  or 
stannous  chloride  in  chlorine  gas.  It  is  a  colorless,  fuming  liquid  which 
boils  at  114°.  With  a  little  water  it  solidifies  to  a  soft  crystalline  mass, 
SnCl4  +  a;H20  (butter  of  tin);  with  more  water  it  dissolves  completely; 
on  boiling  the  solution  insoluble  metastannic  acid  separates  out:  SnCl^H- 
3H20=H2Sn03  +  4HCl.  The  definite  crystalline  double  salt,  SnCl^H- 
2NH4CI,  serves  in  cotton-prmting  as  "pink  salt." 

Stannic  sulphide,  tin  sulphide,  SnSj,  is  obtained  by  treating  a  stannic 
salt  solution  with  sulphuretted  hydrogen.  It  forms  an  amorphous  yellow 
powder  which  is  insoluble  in  dilute  acids.      At  a  red  heat  it  decomposes 


258  INORGANIC  CHEMISTRY. 

into  SnS  +  S.      It  is  soluble  in  alkali  sulphides,  forming  sulphostannates 
which  correspond  to  the  stannates.     Thus: 

(NH,)2S  +  SnS2=  (NHJ^SnSs;     K^S  +  SnS2=  K^SnSg. 

Crystalline  stannic  sulphide  may  be  obtained  in  golden  transparent 
plates  if  amorphous  stannic  sulphide  is  heated  in  the  presence  of  ammo- 
nium chloride.  This  latter  volatilizes  and  so  regulates  the  temperature 
that  no  decomposition  into  SnS  +  S  takes  place.  This  modification  is 
known  as  "mosaic  gold"  or  aurum  musivum,  and  is  used  as  a  bronze;  it 
differs  from  the  other  sulphides  of  tin  by  its  insolubility  in  hydrochloric 
and  nitric  acids. 

d.  Detection  of  Tin  Compounds. 

1.  When  fused  with  soda  on  charcoal  in  the  blowpipe  flame  they 
yield  ductile  metallic  granules  without  incrustation. 

2.  Spongy  metallic  tin  is  separated  from  its  solution  by  metallic 
zinc  in  the  presence  of  free  hydrochloric  acid. 

3.  When  moistened  with  a  cobaltous  solution  and  heated  in  the 
oxidizing  flame  tin  compounds  turn  bluish  green. 

4.  Sulphuretted  hydrogen  precipitates  brown  stannous  sulphide 
from  stannous  salt  solutions,  and  yellow  stannic  sulphide  from  stan- 
nic salt  solutions.  Both  of  these  are  soluble  in  yellow  ammonium 
sulphide,  forming  ammonium  sulphostannate :  SnS+ (NHJjSj  = 
(NHJoSnSj.  Yellow  stannic  sulphide  may  be  precipitated  from 
this  solution  by  acids:    (NH4)2SnS3+2HCl  =  2NH4Cl+H2S+SnS2. 

5.  Stannous  salts  reduce  mercuric  chloride  into  insoluble  mercur- 
ous  chloride  or  into  finely  divided  black  mercury;  stannic  salts  do 
not  give  this  reaction: 

2HgCl,+  SnCl^  =  2HgCl+  SnCl^; 
2HgCl+  SnCl^  =  2Hg+  SnCl,. 

2.  Germanium. 

Atomic  weight  72.5  =  Ge. 

Occurs  only  combined  in  argyrodite,  AggS  +  Ag2GeG3,  as  traces  in 
samarskite,  and  in  euxenite  (p.  248).  It  is  obtained,  by  the  reduction  of 
its  oxides  in  a  current  of  hydrogen,  as  a  brittle  grayish-white  metal  which 
melts  at  about  900°  and  has  a  specific  gravity  of  5.5.  It  imparts  no  colora- 
tion to  the  flame,  and  only  in  the  induction-spark  gives  a  spectrum  which 
consists  of  one  blue  and  one  violet  line.  The  white  germanium  sulphide, 
GeSg,  which  is  insoluble  in  dilute  acids  but  soluble  in  water,  and  which,  like 
tin  sulphide,  forms  with  alkali  sulphides  sulpho  salts,  e.g.,  Kg^eSg,  is 
characteristic.     Argyrodite  contains  silver  sulphogermanate. 


LEAD.  259 

3.  Lead  (Plumbum). 

Atomic  weight  206.9=  Pb. 
Occurrence.      Very    seldom    native,    but   widely    distributed    as 
galena,  PbS,  seldom  as  cerussite,  PbCOg,  wulfenite,  PbMo04,  crocoite, 
PbCr04,  pyromorphite,  Pb3(P04)2'PbCl2,  anglesite,  PbS04,  bournonite, 
(Pb-Cu)SbS3  (p.  181). 

Preparation.     Nearly  entirely  from  galena  by  the  following  methods: 

1.  By  the .  so-called  precipitation  method,  where  the  lead  sulphide  is 
heated  with  scrap-iron:    PbS  +  Fe=Pb  +  FeS. 

2.  By  the  roasting  process.  Lead  sulphide  is  roasted,  wherebv  lead 
oxide  and  lead  sulphate  are  produced:  PbS  +  30=PbO +SO2;  "PbS  + 
40=PbS04.  The  supply  of  air  is  then  shut  off,  when  the  oxidized  com- 
pounds are  transformed  into  lead  by  the  unchanged  lead  sulphide  present: 
PbS  +  2PbO  =  3Pb  +  S02;  PbS  +  PbSO,=  2Pb  +  2SO,. 

This  lead  still  contains  foreign  metals.  The  silver  contained  therein 
is  separated  according  to  the  method  described  (p.  238).  If  this  is  done 
by  the  cupellation  process,  then  the  lead  is  transformed  into  lead  oxide, 
which  is  reduced  again  by  means  of  carbon. 

Properties.  Bluish-gray  shining  metal,  very  soft  and  ductile, 
specific  gravity  11.4.  It  leaves  a  mark  on  paper;  melts  at  335°,  and 
is  then  covered  with  a  gray  scum  called  lead-ash  (PbjO+PbO);  at 
1700°  it  vaporizes,  and  burns  into  lead  oxide  on  the  supply  of  air.  It 
dissolves  readily  in  nitric  acid.  When  compact  it  is  not  attacked 
by  sulphuric  or  hydrochloric  acid,  as  the  lead  sulphate  or  lead  chloride 
formed,  on  account  of  its  insolubility,  protects  the  lead  from 
further  action.  In  the  presence  of  air  it  is  even  attacked  by  weak 
organic  acids,  for  instance  acetic  acid;  hence  it  must  not  be  used 
for  cooking  utensils.  In  dry  air  it  remains  unchanged,  while  in 
moist  air  it  is  covered  with  a  thin  layer  of  PbO.  It  decomposes 
water  only  at  white  heat;  with  water  containing  air  it  forms  in  the 
cold,  on  the  contrary,  lead  hydroxide,  which  is  somewhat  soluble  in 
water. 

The  action  of  air  and  water  on  lead  is  of  importance,  as  lead  pipes  are 
used  in  the  conveyance  of  water,  and  lead  salts  are  poisonous.  Ordinary 
water  varies  in  behavior  towards  lead  according  to  the  salts  contained 
therein.  The  lead  is  more  readily  dissolved  when  chlorides  and  nitrates 
are  present;  but  if,  on  the  contrary,  the  water  is  hard,  containing  car- 
bonates and  sulphates,  then  the  insoluble  coating  of  lead  sulphate  or  lead 
carbonate  which  forms  in  the  lead  pipes  protects  the  metal  from  further 
action,  so  that  the  water  that  flows  through  is  unaffected.  Chemically 
pure  water  does  not  form  any  protective  coating. 

Lead  occurs  divalent  as  plumbous  compounds  and  tetravalent  as 
plumbic  compounds.     Most  plumbous  compounds  are  isomorphous 


260  INORGANIC  CHEMISTRY. 

with  the  corresponding  compounds  of  the  alkaline-earth  group, 
especially  with  the  barium  compounds. 

a.  Alloys  of  Lead. 

Solder  (p.  256),  type-metal  (p.  178),  Rose's  metal  and  Wood's 
metal  (p.  264). 

h.  Plumbous  Compounds. 

Plumbous  oxide,  lead  oxide,  PbO,  is  prepared  by  burning  lead  in 
air,  in  the  separation  of  silver  from  lead  (p.  238),  or  by  heating  lead 
carbonate  or  nitrate.  If  fusion  is  prevented,  it  forms  an  amorphous 
yellow  powder  (Massicot).  When  quickly  cooled  it  forms  a  pale- 
yellow  powder,  and  on  slowly  cooling  a  reddish-yellow  crystalline 
powder,  which  are  given  different  names  (Utharge,  etc.). 

Plumbous  hydroxide,  lead  hydrate,  Pb(0H)2,  is  produced  as  a 
white  precipitate,  somewhat  soluble  in  water,  on  treating  a  lead 
salt  solution  with  alkaU  hydroxide  or  ammonia.  It  decomposes 
into  lead  oxide  and  water  on  heating. 

Plumbous  oxide  and  plumbous  hydroxide  are  converted  by  acid 
into  the  corresponding  salts  and  dissolve  in  an  excess  of  caustic 
alkali,  forming  metaplumbates  (p.  262).  They  absorb  carbon  dioxide 
from  the  air  and  form  basic  lead  carbonate  (p.  261). 

Plumbous  chloride,  lead  chloride,  PbClg,  is  produced  on  treating  a  lead 
salt  solution  with  hydrochloric  acid  or  soluble  chlorides,  which  forms  a 
white  precipitate  slightly  soluble  in  cold  water  but  readily  soluble  in  boil- 
ing water. 

Plumbous  iodide,  lead  iodide,  Pbia,  is  obtained  by  precipitating  a 
plumbous  salt  solution  with  potassium  iodide.  It  forms  a  heavy  yellow 
powder  which  dissolves  in  200  parts  boiling  water,  from  which  crystalline 
golden-yellow  plates  deposit  on  cooling. 

Plumbous  sulphate,  lead  sulphate,  PbSO^,  occurs  naturally  as  angle- 
site,  and  is  isomorphous  with  barium  sulphate;  it  is  formed  at  both 
electrodes  on  the  discharge  of  accumulators  (lead  storage-batteries), 
according  to  the  following  process: 

Pb  +  PbOa  +  2H2SO,^PbSO,  +  PbSO^  +  2H2O, 

Cathode.  Anode.  Cathode.     Anode. 

while  in  charging  the  reverse  process  takes  place  and  the  lead  sulphate  is 
reduced  to  spongy  lead  on  one  side  and  oxidized  to  PbOa  on  the  other 
(p.  261).  It  is  obtained  as  a  white  crystalline  precipitate  on  treating 
a  plumbous  salt  solution  with  sulphuric  acid  or  soluble  sulphates.  Lead 
sulphate  is  insoluble  in  water  and  acids. 

Plumbous  nitrate,  lead  nitrate,  Pb(N03)2,  forms  colorless  octahedral 
crystals  which  are  readily  soluble  in  water  and  which  are  stable  in  the 


LEAD.  261 

Plumbous  silicate  forms  the  chief  constituent  of  flint  and  crystal  glass 
and  the  glaze  of  ordinary  earthenware  (p.  253). 

Plumbous  sulphide,  PbS,  occurs  as  galena  in  regular  crystals  having  a 
bluish-gray  color  (see  also  p.  262,  3). 

Plumbous  carbonate,  lead  carbonate,  PbCOg,  occurs  naturally  as  cerus- 
site,  is  isomorphous  with  aragonite,  etc.  (p.  223).  It  is  obtained  as  a 
white  powder  on  precipitating  a  plumbous  salt  solution  with  ammonium 
carbonate. 

Basic  Plumbous  Carbonate.  If  a  plumbous  salt  solution  is  treated 
with  normal  alkali  carbonates,  white  basic  plumbous  carbonate, 
whose  composition  changes  with  the  temperature  and  concentration 
of  the  solutions,  precipitates  out.  This  may  be  represented  by 
the  formula  7iPbC03+Pb(OH)2,  where  n  =  2,  3,  4,  etc.  A  carbonate 
having  the  formula  2PbC08+Pb(OH)2  is  the  pigment  called  white 
leadf  and  is  prepared  by  the  action  of  carbon  dioxide  upon  basic 
lead  acetate  according  to  various  methods. 

1.  French  Method.  Carbon  dioxide  is  passed  into  a  solution  of  basic 
lead  acetate  (solution  of  lead  oxide  in  lead  acetate),  whereby  the  neutral 
lead  acetate  produced  remains  in  solution,  while  the  white  lead  precipi- 
tates. The  neutral  lead  acetate  is  again  transformed  into  the  basic  salt 
by  dissolving  lead  oxide  therein. 

2.  English  Method.  Lead  oxide  and  lead  acetate  are  rubbed  with 
water  and  carbon  dioxide  passed  through.  The  basic  lead  acetate  here 
formed  is  decomposed  as  described  in  method  1. 

3.  Dutch  Method.  Rolled  sheets  of  lead  are  placed  in  pots  contain- 
ing some  vinegar,  and  these  surrounded  by  manure.  By  the  fermentation 
a  rise  in  temperature  takes  place.  The  vinegar  evaporates  and  forms 
basic  lead  acetate  with  the  aid  of  the  oxygen  of  the  air.  This  is  con- 
verted into  white  lead  and  lead  acetate  by  the  carbon  dioxide  produced 
in  the  fermentation  of  the  manure. 

c.  Plumbic  Compounds, 

Plumbic  oxide,  lead  peroxide,  PbOg,  may  be  considered  as  the  anhy- 
dride of  ortho-  and  metaplumbic  acids;  e.g.,  Pb02  +  2H20=H^Pb04; 
Pb02  +  H20=H2Pb03  (see  below).  It  is  formed  at  the  positive  pole  in 
charging  lead  accumulators  from  the  lead  sulphate  covering  the  lead 
plate  (p.  260).  It  is  also  produced  on  treating  minium,  2PbO  +  Pb02  or 
Pb304,  with  nitric  acid,  when  the  PbO  dissolves,  forming  lead  nitrate,  while 
the  Pb02  remains  as  an  insoluble  dark-brown  amorphous  powder: 
Pb304  +  4HN03=Pb02  +  2Pb(N03)2  +  2H20.  If  reducing  bodies,  such  as 
sugar,  oxalic  acid,  etc.,  be  added  at  the  same  time,  then  the  PbOg  is  reduced 
to  PbO  and  then  dissolves  in  nitric  acid. 

On  heating  lead  peroxide  decomposes  into  PbO  and  O ;  warmed  with 
hydrochloric  acid  it  forms  lead  chloride  with  the  development  of  chlorine, 
and  with  sulphuric  acid  it  forms  lead  sulphate  with  the  generation  of 
oxygen: 

Pb02+H2SO,=PbSO,+H20  +  0; 

Pb02  +  4HC1  =PbCl2  +  2H20  +  2Cl. 


INORGANIC  CHEMISTRY, 

Orthoplumbic  acid,  plumbic  hydroxide,  Pb(0H)4,  is  known  only  in  the 
form  of  salts,  the  orthoplumbates. 

Calcium  orthoplumbate,  Ca2Pb04,  is  formed  on  heating  CaO  with  lead 
oxide  or  lead  peroxide  in  the  air.  It  is  a  yellowish  mass  which  is  used  in 
Kassner's  method  for  preparing  oxygen. 

Lead  orthoplumbate,  PbgCPbO^)  or  Pb304,  minium,  red  lead,  is  ob- 
tained by  heating  PbO  in  the  air  to  300°-400°,  and  forms  a  scarlet  red 
crystalline  powder  that  on  heating  above  400°  gives  off  oxygen  and  is 
transformed  again  into  lead  oxide.  With  acids  its  behavior  is  like  that 
of  a  mixture  of  2PbO  +  Pb02  (^^^  ^^is  latter). 

Metaplumbic  acid,  HaPbOg,  forms  on  the  positive  pole,  on  the  electroly- 
sis of  lead  salts,  as  a  bluish-black  body. 

Sodium  metaplumbate,  NagPbOg  +  SHgO,  is  obtained  as  colorless  crys- 
tals on  carefully  evaporating  a  solution  of  PbOa  in  caustic  potash  solution : 
Pb02  +  2NaOH  =  Na2Pb03  +  H20.  The  watery  solution  gives  with  many 
metallic  salt  solutions  a  precipitate  of  the  corresponding  metaplumbate. 

Lead  metaplumbate,  Pb(Pb03),  is  precipitated  from  the  solution  of 
PbO  in  caustic  alkali  by  NaClO  as  a  reddish-yellow  powder. 

Plumbic  chloride,  lead  tetrachloride,  PbCl^,  is  obtained  on  dissolving 
PbOj  in  ice-cold  hydrochloric  acid  and  treating  the  solution  with  NH^Cl, 
when  yellow  crystals  of  PbCl^  +  2NH4CI  separate  out.  If  these  crystals 
are  introduced  into  ice-cold  sulphuric  acid,  the  PbCl^  is  set  free  as  a  yel- 
low liquid  which  crystallizes  at  —15°. 

Plumbic  sulphate,  Pb (804)2,  is  produced  on  the  electrolysis  of  sul- 
phuric acid,  making  use  of  lead  electrodes,  and  is  a  yellowish-white  crystal- 
fine  powder  which  decomposes  with  water: 

Pb(S04)2  +  2H20=  PbOj  +  2H2SO4. 
d.  Detection  of  Lead  Compounds. 

1.  They  color  the  non-luminous  flame  pale  blue.  The  spectrum 
shows  characteristic  lines  in  the  green  part. 

2.  Heated  with  soda  upon  charcoal  they  yield  soft  metallic 
granules  of  lead  and  a  yellow  coating  of  lead  oxide. 

3.  Sulphuretted  hydrogen  precipitates  black-lead  sulphide  from 
solutions  of  lead  salts.  This  is  insoluble  in  alkali  sulphides  and 
dilute  acids. 

4.  Caustic  alkali  precipitates  white  lead  hydroxide  soluble  in 
an  excess  of  the  precipitant. 

5.  Sulphuric  acid  precipitates  white  lead  sulphate  soluble  in 
caustic  alkali  and  in  basic  ammonium  tartrate. 

6.  Zinc  and  iron  precipitate  lead  from  its  solutions  in  metallic 
shining  plates  (lead-tree). 

4.  Titanium. 

Atomic  weight  48.1  =  Ti. 

Occurs  only  in  combination,  chiefly  as  TiOg  in  the  minerals  anatase, 
rutile,  and  brookite,  which  differ  from  each  other  only  in  crystalline  form.    It 


ZIRCONIUM.— THORIUM.— BISMUTH.  263 

is  also  found  in  euxenite  and  oerstedite,  and  to  a  less  extent  in  many  rocks 
and  in  many  iron  ores.  The  metal  is  obtained  by  heating  potassium-titan- 
ium fluoride,  KgTiFg,  with  potassium.  It  forms  an  iron-gray  crystalline 
powder  having  a  specific  gravity  of  3.55. 

5.  Zirconium. 

Atomic  weight  90.6= Zr. 

Zirconiurn  occurs  only  in  combination,  especially  as  zircon  or  hyacinth, 
ZrSiO^,  also  in  wohlerite,  oerstedite,  and  is  obtained  in  the  same  manner 
as  titanium.  It  is  known  in  three  allotropic  modifications,  namely,  as 
gray  crystals  having  a  specific  gravity  of  4.15,  as  graphitic  zirconium,  and 
as  a  black  powder. 

Zirconium  oxide,  zirconia,  ZrOg,  on  heating  glows  with  an  intense  light 
and  is  used  as  the  illuminating  body  for  the  oxyhydrogen  flame  (zircon 
pencils)  (p.  113). 

6.  Thorium. 
Atomic  weight  232.5=  Th. 

Occurs  only  combined  in  thorite,  ThSi04,  and  with  the  rare  earthy 
metals  in  many  of  the  minerals  mentioned,  on  p.  248.  It  is  prepared 
in  an  analogous  manner  to  titanium  and  forms  a  gray  powder  having 
a  specific  gravity  of  11.0.  Thorium  oxide,  thoria,  ThOj,  glows  at  a 
much  lower  temperature  than  zirconium  oxide  and  with  a  more 
intense  light,  especially  when  it  contains  one  per  cent,  of  cerium 
dioxide,  CeOz-  This  mixture  serves  in  the  preparation  of  the  mantle 
for  the  Welsbach  light,  which  is  produced  when  a  cotton  tissue  impreg- 
nated with  thorium  nitrate,  Th(N03)4,  and  cerium  nitrate,  CeCNOg),, 
is  heated.  Both  of  these  salts  are  prepared  on  a  large  scale  from 
monazite  sand  or  cerite. 

BISMUTH  GROUP. 

Bismuth.     Vanadium.     Niobium.     Tantalum. 

These  elements  appear  trivalent  and  pentavalent  and  belong  to  the 
nitrogen  group  (p.  145).  Vanadium,  niobium,  and  tantalum  are  not 
precipitated  by  HgS  from  their  acid  nor  from  their  neutral  solutions. 

I.   Bismuth. 

Atomic  weight  208.5=  Bi. 
Occurrence.     Chiefly  native,  as  well  as  bismite  or  bismuth  ocher, 
Bi203,  bismuthinite,  BiSg,  eulytite,  Bi4(Si04)3,  seldom  as  tetradymite, 

Bi^TCg+Bi^Sg. 

Preparation.  It  is  separated  from  the  rocks  by  fusion;  from 
the  ores  by  roasting  and  reduction  of  the  obtained  bismuth  oxide 
by  carbon. 


264^  INORGANIC  CHEMISTRY, 

Properties.  Reddish-white  brittle  metal  having  a  specific  grav- 
ity of  9.8,  melting  at  268°,  and  which  on  slowly  coohng  crystal- 
lizes in  rhombohedra  (isomorphous  with  As  and  Sb)  very  similar 
to  cubes.  It  is  stable  in  the  air,  vaporizes  at  about  1300°,  and  on 
heating  it  burns  into  bismuth  trioxide.  It  decomposes  water  at  a 
red  heat.  It  is  the  poorest  conductor  for  heat  of  the  metals,  and 
expands  on  cooling.  It  is  insoluble  in  hydrochloric  acid  and  dilute 
sulphuric  acid,  but  dissolves  in  cold  nitric  acid  and  in  hot  concen- 
trated sulphuric  acid,  with  the  development  of  nitric  oxide  and  sul- 
phur dioxide  respectively,  forming  the  corresponding  salts: 

2Bi+ 8HNO3  =  2Bi(N03)3+ 4H2O+ 2N0; 

2Bi+  6H2SO,  =  Bi2(SO,)3+  6H,0+  SSOj. 

a.  Alloys  of  Bismuth 

are  characterized  by  their  ready  fusibility  and  are  used  in  the  making 

of  stereotypes,  etc.;    Rose's  metal  (Sn.Pb.Bi)  melts  at  94°,  Wood's 

metal  (Sn.Pb.Bi.Cd)  melts  at  63^. 

b.  Compounds  of  Bismuth. 

Bismuth  trioxide,  BigOj,  is  obtained  by  burning  bismuth  or  heating 
bismuth  nitrate,  hydroxide,  or  pentoxide  as  a  yellow  powder  insoluble  in 
water  and  in  caustic  alkalies. 

Bismuth  hydroxide,  Bi(0H)3,  is  precipitated  from  bismuth  salt  solu- 
tions by  caustic  alkali,  and  forms  an  amorphous  powder  which  is  insoluble 
in  water  and  caustic  alkalies,  and  at  100°  is  transformed  into 

Metabismuth  hydroxide,  HBiOa  or  OBi(OH),  which  when  dry  forms 
a  white  amorphous  mass :   H 36103=  HgO  +  HBiOg. 

Bismuth  tetr oxide,  BiaO^,  is  obtained  as  a  yellowish-brown  powder 
by  the  prolonged  action  of  nitric  acid  upon  bismuth  pentoxide. 

Bismuth  pentoxide,  bismuthic  anhydride,  BigO.,  is  obtained  by  heat- 
ing metabismuthic  acid,  and  forms  a  brown  powder  that  behaves  like  a 
superoxide  towards  acids. 

Bismuthic  acid,  HgBiO^,  which  is  analogous  to  phosphoric  acid,  is  not 
known,  but 

Metabismuthic  acid,  HBiOg,  which  is  analogous  to  metaphosphoric 
acid,  is  known.  This  is  formed  on  passing  chlorine  gas  into  caustic  alkali 
in  which  BiaOg is  suspended,  when  red  potassium  bismuthate  separates  out; 
this  can  be  decomposed  by  boiling  nitric  acid  into  metabismuthic  acid, 
which  forms  a  scarlet-red  powder  and  which  behaves  like  BiaOj  towards 
acids. 

Bismuth  salts,  BigOg  and  HBiOg,  differ  from  the  other  analogous  com- 
pounds of  the  nitrogen  group  in  having  basic  properties  and  being  insol- 
uble in  alkalies.  By  dissolving  them  in  acids  and  evaporating  to  crystal- 
lization the  normal  bismuth  salts  are  obtained;  e.g., 

BiClg;  Bi(N03)3  +  5H20;  Bi2(SO,)3;  BiPO,. 

Basic  Bismuth  Salts.    The  salts  of  bismuth  are  soluble  in  a  small  quan- 


VANADIUM,— NIOBIUM.— TANTALUM.  265 

tity  of  water,  but,  like  those  of  antimony,  are  decomposed  by  considerable 
water  and  basic  bismuth  salts  separate  out,  depending  upon  the  tempera- 
ture and  concentration  of  the  solution.     Ihus: 

BiClg        +   H^O^BiOCl  +2HC1; 

Bi(N03)3  +  2H20=Bi(OH)2N03  +  2HN03; 
Bi^CSO  4)3  +  4H2O  =  Bi2(0H),S0,  +  2H2SO,. 

Bismuth  subnitrate  is  obtained  on  mixing  a  concentrated  solution  of 
bismuth  nitrate  with  twenty-five  times  its  volume  of  boiling  water,  which 
forms  a  white  microcrystalline  powder: 

2Bi(N03)3  +  3H20=[Bi(OH)2N03  +  BiO(N03)]+4HNO^. 
c.  Detection  of  Bismuth  Compounds. 

1.  Considerable  water  precipitates  white  basic  bismuth  salts 
from  bismuth  salt  solution.  This  basic  bismuth  salt  is  insoluble  in 
tartaric  acid,  differing  in  this  respect  from  the  corresponding  anti- 
mony compounds. 

2.  Sulphuretted  hydrogen  precipitates  brownish-black  bismuth 
sulphide,  Bi^^^,  which  is  insoluble  in  dilute  acids  and  alkali  sulphides. 

3.  Mixed  with  soda  and  heated  upon  charcoal  brittle  granules 
of  metallic  bismuth  and  a  yellowish-brown  incrustation  of  bismuth 
trioxide  are  obtained. 

2.  Vanadium. 

Atomic  weight  51.2=  V. 

It  occurs  only  in  combination,  as  dechenite,  Pb(V03)2,  as  vanadinite, 
Pb3(V04)2,  as  carnotite,  and  in  the  Thomas  slag  from  Creuzot.  The  metal 
is  obtained  by  heating  VCI3  in  a  current  of  hydrogen  which  gives  a  gray 
powder  having  a  specific  gravity  of  5.5  and  melting  at  about  3000° 

3.  Niobium  (Columbium).  4.  Tantalum. 

Atomic  weight  94= Nb.  Atomic  weight  183= Ta. 

Are  found  only  in  combination  and  in  fact  always  together  as  colum- 
bite  and  tantalite,  both  03Ta~Fe~Nb03,  also  in  euxenite,  yttrotantalite, 
pyrochlore,  wohlerite  (p.  248).  They  are  prepared  in  the  same  way  as 
vanadium  and  form  gray  metallic  powders  whose  properties  in  a  pure 
state  are  not  well  known. 

CHROMIUM  GROUP. 

Chromium.  Molybdenum.  Tungsten.  Uranium. 
Just  as  the  metallic  elements  Sn,  Zr,  Ti,  Th  are  related  to  the  car- 
bon group  and  the  elements  Bi,  Va,  Nb,  Ta  to  the  nitrogen  group,  so 
the  elements  Cr,  Mo,  W,  and  more  remotely  U,  are  related  to  the  sulphur 
group.  Chromium  forms  the  connecting  member  of  this  group  with  that 
of  iron  and  aluminium,  as  its  compounds  are  closely  related  to  those  of 
iron  on  the  one  side  and  to  those  of  aluminium  on  the  other.     They  are 


266  INORGANIC  CHEMISTRY, 

stable  in  the  air  and  decompose  water  only  at  a  red  heat;  chromium  and 
tungsten  compounds  are  not  precipitated  from  their  acid  or  neutral  solu- 
tions by  sulphuretted  hydrogen. 

1.  Hexavalent  they  form,  like  the  elements  of  the  sulphur  group,  tri- 
oxides  which  are  acid  anhydrides.  They  form  salts  having  a  constitution 
analogous  to  that  of  the  manganates  and  ferrates,  although  they  are  more 
stable,  many  of  them  being  similar  and  isomorphous  with  the  sulphates: 
e.g.,  K^CrO^,  K^oO,. 

2.  Tetravalent  they  form  (with  the  exception  of  chromium)  com- 
pounds corresponding  to  the  elements  of  the  sulphur  group:  e.g.,  UO,. 
koO„  W0„  UCl,. 

3.  Chromium  and  molybdenum  may  form  trivalent  compounds  which 
are  very  similar  to  the  trivalent  compounds  of  the  iron  and  the  aluminium 
group;  e.g.,  CrPg,  CrClg. 

4.  With  the  exception  of  uranium,  they  form  divalent  compounds,  of 
which  those  of  chromium  are  very  similar  to  the  magnesium  group  and 
the  ferrous  compounds,  although  they  are  less  stable;  e.g.,  CrClg.  The 
corresponding  oxygen  salts  of  tungsten  and  molybdenum  are  not  known. 

5.  Molybdenum,  tungsten,  and  uranium  also  occur  pentavalent,  molyb- 
denum and  uranium  also  octavalent,  chromium  also  nonovalent. 

I.  Chromium. 

Atomic  weight  52.1  =  Cr. 

Occurrence.  Never  native,  generally  as  chromite  or  chrome-iron 
ore,  Fe(Cr:02)2j  seldom  as  crocoite,  PbCr04. 

Preparation.     By  heating  chromic  oxide  with  aluminium  (p.  248). 

Properties.     Pale-gray  shining  metal  having  a  specific  gravity  of 

6.8  whose  fracture  shows  large  crystals.      It  is  one  of  the  hardest 

and  most  refractory  (at  about  3000°)  of  the  metals;  it  is  non-magnetic, 

oxidizes  only  slowly  on  heating,  but  burns  into  chromic  oxide  on 

heating  to  a  white  heat  in  oxygen.     It  dissolves  in  hydrochloric 

acid  with  the  evolution  of  hydrogen,  forming  CrCla,  and  in  sulphuric 

acid,  producing  CrS04,  but  is  insoluble  in  nitric  acid. 

After  lying  in  the  air  chromium  does  not  dissolve  in  dilute  acids  (inac- 
tive chrornium).  But  on  heating  it  with  the  acid  it  begins  to  dissolve, 
and  this  continues  after  washing  it  off  and  placing  it  in  the  cold  acid 
(active  chromium). 

Divalent  chromium  forms  chromous  compounds,  trivalent  the 
chromic  compounds,  hexavalent  forms  chromium  trioxide  and  the 
chromates.  All  the  compounds  of  chromium  are  characterized  by 
their  beautiful  color  (xpc^ua,  color). 

a.  Alloys  of  Chromium 
with  iron  are  used  as  chrome-steel. 


CHROMIUM,  267 


h.  Chromous  Compounds. 

These  are  little  known,  as  they  have  great  power  of  absorbing  oxgyen 
and  being  converted  into  chromic  salts. 

Chromous  oxide,  CrO,  is  not  known. 

Chromous  hydroxide,  Cr(0H)2,  is  obtained  by  treating  chromous 
chloride  with  caustic  alkali,  which  gives  a  yellow  precipitate  that  is 
quickly  converted  into   chromic    oxide  with  the  evolution  of  hydrogen: 

2Cr(OH)2= CrA  +  H2O  +  2H. 

Chromous  chloride,  CrClj,  is  obtained  by  passing  hydrogen  over  heated 
chromic  chloride  which  yields  a  white  crystalline  powder  forming  a  blue 
solution  with  water.  This  solution  takes  up  oxygen  with  activity  and  be- 
comes green  with  the  probable  formation  of  Cr20Cl4(?). 

c.  Chromic  Compounds. 

These  are  prepared  analogously  to  the  corresponding  aluminium  com- 
pounds. 

Chromic  oxide,  chromium  sesquioxide,  CrgOg,  an  amorphous  green 
powder  nearly  insoluble  in  acids,  is  produced  on  heating  Cr(OH)3  or  CrOg. 
It  may  be  obtained  in  black  crystals  isomorphous  with  AI2O3  and  Fe^Og^ 
by  passing  the  vapors  of  chromyl  chloride  through  a  red-hot  tube: 

2CrO,Cl2=Cr20  -f-4Cl  +  0. 

Chromic  hydroxide,  Cr(0H)3,  is  precipitated  from  chromic  salt  solu- 
tions by  caustic  alkalies  or  ammonia  as  a  bluish-gray  precipitate  which, 
like  A1(0H)3,  behaves  Hke  a  weak  acid  and  is  soluble  in  an  excess  of  caustic 
alkali  (p.  270),  and  precipitating  again  on  boiling.  On  the  other  hand  it 
acts  Hke  a  weak  base,  like  A1(0H)3  and  Fe(0H)3,  but  not  combining  with 
the  weak  acids,  such  as  carbonic  acid,  sulphurous  acid,  sulphuretted  hydro- 
gen. On  heating  to  200°  in  a  current  of  hydrogen  it  is  converted  into 
metachromic  hydroxide,  HCrOa  or  CrO(OH),  which  is  bluish  gray  and 
insoluble  in  dilute  hydrochloric  acid.  The  hydrate  Cr,0(OH)^  is  used  as 
the  beautiful  pigment  called  Guignet  s  green. 

Chromites  are  the  compounds  corresponding  to  the  aluminates  (p.  251) 
and  are  derived  from  HCrOa,'  e.g.,  Mg(Cr02)2. 

Chromic  salts  are  obtained  by  dissolving  chromic  hydroxide  in  the 
respective  .acids  and  evaporating  at  as  low  a  temperature  as  possible. 
They  form  violet  crystals,  producing  a  violet  solution  in  cold  water;  on 
heating  this  solution  they  become  green  and  on  evaporation  yield  amor- 
phous green  masses  which  consist  of  a  mixture  of  basic  and  acid  chromic 
salts.  If  the  green  salts  are  dissolved,  then  the  solution  gradually  becomes 
violet,  and  on  careful  evaporation  violet  crystals  of  the  neutral  chromic 
salts  separate  out. 

Potassium-chromium  sulphate,  chrome  alum,  KCr(S04)2  +  12H20  (p. 
252) ,  forms  deep-violet  octahedra  and  is  obtained  by  the  action  of  sulphur 
dioxide  upon  a  solution  of  potassium  dichromate  treated  with  sulphuric 
acid  and  evaporating  the  same:  K2Cr207  +  H2S04+3S02=2KCr(SOj2  + 
H2O, 


268  INORGANIC  CHEMISTRY. 

d.  Higher  Chromium  Compounds. 
Chromium  trioxide,  chromic  anhydride,  CrOg,  is  formed  on  the 

electrolysis  of  chromic  sulphate,  as  well  as  on  treating  a  concentrated 
solution  of  potassium  dichromate  with  an  excess  of  concentrated 
sulphuric  acid:  K2Cr207+H2SO,  =  K2S04+2Cr03+H20.  On  cooHng 
the  chromium  trioxide  crystaUizes  out  in  long  scarlet-red  rhombic 
crystals;  it  is  deliquescent,  readily  soluble  in  water,  melts  on  heating, 
forming  a  deep-red  liquid,  and  decomposes  at  250° :  2Cr03  =  Cr203+  30. 
It  has  an  energetic  oxidizing  action,  so  that  it  destroys  many  organic 
bodies  (hence. its  solution  cannot  be  filtered  through  paper);  when 
poured  upon  alcohol  a  faint  explosion  occurs,  reducing  it  into 
chromic  oxide.  It  is  not  attacked  by  nitric  acid;  with  hydro- 
chloric acid  it  yields  chromic  chloride  with  the  generation  of  chlorine, 
and  with  sulphuric  acid  it  forms  chromic  sulphate  with  the  develop- 
ment of  oxygen: 

CrOg+eHCl     =CrCl3       -FSH^O+SCl; 
2Cr03+  3H2SO4  =  Cr2(S04)3+  ZYi.O^  30. 

Chromyl  chloride,  chromium  oxychloride,  Cr02C]2  (chromium  trioxide 
in  which  one  atom  of  oxygen  is  replaced  by  two  atoms  of  chlorine),  is  pre- 
pared by  distilling  alkali  dichromates  with  common  salt  and  an  excess  of 
sulphuric  acid  (to  combine  with  the  water).  It  forms  a  fuming,  deep-red 
liquid  which  decomposes  with  water  into  chromium  trioxide  and  hydro- 
chloric acid: 

K^Cr.O^  +  4NaCl  +  SH^SO,  =  2Na2SO,  +  K^SO,  +  2Cr02Cl2 + ZYL.O ; 
CrO^Cls  +  H2O = CrOg  +  2HC1. 

(The  formation  of  CrO^Clg  serves  to  detect  the  presence  of  chlorine  in 
the  presence  of  bromine  and  iodine  compounds,  these  last  two  not  form- 
ing an  analogous  compound.) 

Chromic  acid,  H2Cr04  or  HO-CrOz'^OH,  separates  on  cooling  the 
watery  solution  of  chromium  trioxide  to  0°  in  red  needles.  On  warm- 
ing the  solution,  it  decomposes  immediately  again  into  H^O+CrOg, 
which  latter  remains  behind  on  the  evaporation  of  the  solution. 

Chromates  form  yellow  crystals  and  are  prepared  by  fusing  the 
chromium  compound  with  bases  and  an  oxidizing  agent  (see  Sodium 
Dichromate),  or  by  the  action  of  bases  upon  CrOg;  e.g.,  2NaOH-|- 
CrO.^=Na2Cr04-|-H20.  The  chromates  of  the  heavy  metals  and  of 
barium  are  insoluble  in  water. 

Polychromic  acids,  H2Cr044-a'CrOg,  may  be  considered  as  ob- 
tained by  the  removal  of  H2O  from  several  chromic  acid  molecules; 


J 


CHROMIUM,  269 

e.g.,  2H2Cr04=H20+H2Cr207  (dichromic  acid),  3H2Cr04  =  2H20+ 
H2Cr30io  (trichromic  acid).  These  acids  are  not  known  free,  as  they 
decompose  immediately  on  being  formed:  H2Cr207  =  2Cr03+H20; 
H2Cr30io  =  3Cr03+H20.  Their  red  crystaUine  salts,  the  polychrp- 
mates,  are  prepared  from  the  chromates  by  the  action  of  cold  acids, 
and  are  transformed  into  chromates  by  the  action  of  bases.  On 
heating  to  a  red  heat  the  polychromates  give  off  oxygen,  and  on 
heating  with  acids  they  behave  hke  peroxides  (see  Potassium  and 
Sodium  Dichromate). 

Perchromic  acid,  HCrOg  or  HQ-CrO^,  is  known  only  in  the  form  of  deep 
violet  salts  and  as  an  unstable  deep-blue  anhydride,  Cr  O^  (see  Hydrogen 
Peroxide,  p.  119),  both  of  these  being  readily  decomposable,  the  first 
producmg  dichromates  and  the  second  chromium  trioxide,  and  at  the  same 
time  an  evolution  of  oxygen. 

Sodium  chromate,  Na2CrO,  + lOH^O,  isomorphous  with  sodium  sul- 
phate, crystallizmg  from  its  aqueous  solution  below  18°,  and  crystallizing 
at  18°-20°  as  NagCrO^  +  GHgO,  and  as  anhydrous  crystals  at  30°,  It  is 
prepared  analogously  to  potassium  chromate,  forming  yellow  deliquescent 
crystals.     For  the    preparation  on   a  large  scale  see  Sodium  Dichromate. 

Potassium  chromate,  yellow  chromate,  KgCrO^,  is  obtained  by  treating 
a  potassium  dichromate  solution  with  caustic  potash:  K2Cr207  +  2KOH= 
2K2Cr04  +  H20,  and  is  produced  on  fusing  every  chromium  compound 
with  potassium  carbonate  and  saltpeter  (p.  270).  It  forms  yellow 
masses  which  dissolve  in  water,  and  on  evaporation  yields  yellow  rhombic 
crystals  isomorphous  with  potassium  sulphate  and  potassium  man- 
ganate;  on  heating  with  concentrated  acids  the  chronr.ates  act  like  the 
dichromates. 

Lead  chromate.  Chromate  yellow,  PbCr04,  occurs  as  crocoite.  It  is 
obtained  as  a  yellow  precipitate  by  precipitating  a  lead  salt  solution  with 
potassium  chromate.  (Used  as  a  paint  under  the  name  chrome  yellow, 
Parisian  yellow,  Leipzig  yellow,  Hamburg  yellow.)  At  a  red  heat  it  decom- 
poses with  the  generation  of  oxygen,  which  oxidizes  all  organic  bodies; 
hence  it  is  used  like  copper  oxide  in  the  combustion  of  organic  bodies  in 
their  elementary  analysis.  It  dissolves  in  an  excess  of  caustic  alkali ;  if  a 
little  caustic  alkali  is  added,  and  it  is  then  warmed,  it  becomes  red  with 
the  formation  of  basic  lead  chromate,  PbO  +  PbCrO^,  which  is  used  as  a 
pigment  (chrome-red,  orange-red,  cinnabar-red,  carmine-red): 

2PbCr04  +  2K0H=  (PbO  +  PbCrO,)  +  K2Cr04  +  H2O. 

Potassium  dichromate,  Red  Chromate,  Double  Potassium  Chromate, 
Acid  Potassium  Chromate,  KoCr207.  If  a  saturated  solution  of  potassium 
chromate  is  treated  with  enough  sulphuric  acid  to  combine  with  one-half 
of  the  potassium  (p.  268),  then  on  cooUng  potassium  dichromate  separates 
out.  On  a  large  scale  it  is  obtained  by  treating  sodium  dichromate  with 
potassium  chloride,  when  on  evaporation  the  sodium  chloride  first  crys- 
tallizes out : 

Na2Cr207  +  2KC1=  K^CvJd,  +  2NaCl. 

It  forms  large  red  triclinic  crystals  soluble  in  ten  parts  of  water.    On 


270  INORGANIC  CHEMISTRY. 

heating   it  melts  without  decomposition;    on  heating  to  a  red  heat   it 
decomposes  into  potassium  chromate,  chromic  oxide,  and  oxygen: 

2K2Cr207=2K,CrO,+Cr203+30. 

When  heated  with  concentrated  suphuric  acid  it  yields  chrome  alum 
and  pure  oxygen  (method  of  preparing  oxygen) : 

KgCrPy  +  4H2SO,=  2KCr(S04),  +  4H2O + 30. 

When  heated  with  concentrated  hydrochloric  acid  it  forms  chromic 
chloride,  and  chlorine  is  evolved: 

K^Cr^O^  +  14HC1  =  2KC1  +  2CrCl3  +  TH^O  +  6C1. 

Sodium  dichromate,  NagCraOy  +  2H2O,  is  the  substance  from  which  all 
chromium  compounds  are  prepared.  Chrome-iron  ore  is  heated  with  cal- 
cium oxide  and  an  abundant  supply  of  air;  the  calcium  chromate  formed 
is  converted  into  sodium  chromate  by  heating  it  with  a  soda  solution. 
This  sodium  chromate  is  treated  with  the  proper  quantity  of  sulphuric 
acid,  when  from  the  hot  solution  anhydrous  sodium  sulphate  separates,  and 
on  evaporation  sodium  dichromate,  in  the  form  of  red  triclinic  crystals,  is 
obtained,  which  is  only  slightly  soluble  in  water: 

2Fe(Cr02)2  +  4CaO  +  70  =  4CaCrO,  +  Fe^Og; 
CaCrO^  +  Na2C03=  Na^CrO^  +  CaCOg ; 
2Na2CrO,  +  H^SO,  =  NagCrgO^  +  NagSO,  +  HjO. 

e.  Detection  of  Chromium  Compounds. 

Chromium  Salts.  1.  They  color  the  borax  bead  in  the  blowpip© 
flame  emerald-green. 

2.  Caustic  alkalies  precipitate  green  chromic  hydroxide,  which 
dissolves  in  an  excess  of  the  alkali  with  a  green  color,  and  on  boiling 
the  solution  separates  completely.  (Separation  from  aluminium  hy- 
droxide, which  remains  in  solution  on  boiling  its  alkahne  solution.) 

3.  Ammonia  or  ammonium  sulphide  precipitates  green  chromic 
hydroxide,  which  is  only  very  slightly  soluble  in  an  excess. 

4.  Sulphuretted  hydrogen  does  not  precipitate  chromium  salts. 

5.  On  fusion  with  soda  and  saltpeter  they  all  give  a  yellow  mass 
(p.  269)  whose  solution  acidified  with  acetic  acid  gives  the  reactions 
for  the  chromates. 

Chromates.  1.  They  are  transformed  into  chromium  salts  by 
reducing  bodies,  e.g.,  H2S,  SO2,  oxahc  acid,  alcohol;  hence  their 
yellow  or  red  solution  turns  green  (see  Potassium-chromium  Alum, 
p.  267). 

2.  Caustic  alkahes,  ammonia,  ammonium  sulphide  produce  no 
precipitation  in  chromate  solutions. 

3.  Lead  salts  precipitate  yellow  lead  chromate  from  their  neutral 


MOLYBDENUM.— TUNGSTEN.  271 

solution,  PbCr04  (p.  269);  barium  salts,  yellow  barium  chromate, 
BaCr04  (p.  226);  silver  salts,  red  silver  chromate,  Ag2Cr04. 
4.  By  transforming  them  into  perchromic  acid  (p.  119). 
a.  Molybdenum. 

Atomic  weight  96= Mo. 
Occurs  only  combined  in  molybdenite,  MoSg,  wulfenite,  PbMoO^.  It 
is  obtained  by  heating  its  oxides  with  aluminium,  which  forms  a  silver- 
white  metal,  malleable,  relatively  soft,  having  a  specific  gravity  of  9, 
fusing  at  about  1900°,  and  being  soluble  only  in  concentrated  sulphuric 
acid,  nitric  acid,  and  aqua  regia. 

Compounds  of  Molybdenum. 

Molybdenum  trioxide,  molybdic  anhydride,  M0O3,  is  obtained  on  roast- 
ing molybdenum  or  molybdenite  which  yields  white  crystals  that  are 
readily  soluble  in  ammonia  or  caustic  alkalies,  producing  molybdates, 
and  insoluble  in  water  and  acids. 

Molybdic  acid,  H2M0O4,  is  precipitated  as  yellow  crystals  from  the 
molybdates  by  means  of  nitric  acid. 

Phosphomolybdic  acid  (Sonnenschein's  reagent),  H3PO4  +  IIM0O3, 
serves  as  a  precipitant  for  alkali  salts  and  alkaloids  (which  see). 

Ammonium  molybdate,  (NHJ2M0O4,  is  a  reagent  and  precipitant  for 
phosphoric  acid  and  arsenic  acid  (see  these). 

Molybdenum  trisulphide,  M0S3,  is  obtained  as  a  black  precipitate  by 
treatmg  acidified  molybdenum  salt  solutions  with  HoS.     It  is  soluble  in 
alkali  sulphides,  forming  alkali  sulphomolybdates ;   e.g.,  K2M0S4. 
3.  Tungsten  (Wolfram). 
Atomic  weight  184=  W. 

Occurs  only  combined  as  wolframite,  FeW04,  as  tungsten  or  scheelite, 
BaW04,  or  more  seldom  stolzite,  PbW04.  By  the  reduction  of  its  oxides 
with  aluminium  (p.  248)  it  is  obtained  as  a  white,  very  hard,  brittle 
metal  of  a  specific  gravity  of  16.6,  and  fusible  at  about  2000°.  On  heating, 
as  well  as  by  warming  with  nitric  acid  or  aqua  regia,  it  is  converted  into 
insoluble  WO3.  Tungsten  is  insoluble  in  hydrochloric  or  sulphuric  acids. 
It  is  prepared  on  a  large  scale  in  order  to  produce  an  especially  hard  form 
of  steel  (tungsten  steel). 

Compounds  of  Tungsten. 

Tungsten  trioxide,  WO3,  is  produced  by  treating  finely  powdered  tung- 
sten ore  or  tungsten  with  nitric  acid.  It  forms  a  yellow  powder  which 
readily  dissolves  in  alkalies  or  ammonia,  forming  the  corresponding  salts, 
the  tungstates  or  wolframates,  but  is  insoluble  in  acids. 

Tungstic  acid,  wolframic  acid,  H4WO5,  which  is  readily  converted 
into  H4WO4,  is  precipitated  as  yellow  crystals  from  solutions  of  tung- 
states by  nitric  acid.  Peculiarly  constituted  alkali  tungstates,  K2W40j2, 
have  a  metallic  luster  and  various  colors,  and  are  used  as  tungsten  bronzes. 

Sodium  tungstate,  Na2W04  +  2H20,  is  used  as  a  mordant  in  calico- 
printing,  as  well  as  to  make  tissues  non-inflammable. 

Calciimi  tungstate,  CaW04,  serves  in  the  detection  of  the  Rontgen  rays, 
which  give  a  bluish-violet  fluorescence  therewith. 

Phosphotungstic  acid,  H3PO4  +  IIWO3  (Scheibler's  reagent),  is  used  for 
the  same  purposes  as  phosphomolybdic  acid. 


272  INORGANIC  CHEMISTRY. 

4.  Uranium. 

Atomic  weight  238.5=  U. 

Occurs  only  combined  and  chiefly  as  uraninite,  UO2  +  2UO3  (called 
pitchblende).  It  is  obtained  by  heating  uranium  oxides  with  aluminium, 
or  by  the  reduction  of  UCI4  with  sodium,  as  a  silver-white,  hard,  brittle 
metal  of  a  specific  gravity  of  18.7,  which  melts  at  about  1500°,  is  soluble 
in  dilute  acids,  and  which  burns  when  heated  into  uranic-uranous  oxide 
UO2  +  2UO3. 

Compounds  of  Uranium. 

It  occurs  tetravalent  in  the  unstable  uranous  compounds,  and  hexa- 
valent  in  the  uranic  compounds.  These  latter  all  contain  the  divalent 
radical  UOg,  called  uranyl: 

(U02)0,  Uranyl  oxide.  (U02)Cl2,    Uranyl  chloride. 

(UOaXNOg)^,  Uranyl  nitrate.        (U02)S0„  Uranyl  sulphate. 
Many  uranium  salts  have  a  beautiful  fluorescence.     Uranium  and  all 
its  compounds  have  the  property  of  acting  upon  photographic  plates  (p. 
241)  through  black  paper,  and  also  of  causing  the  illumination  of  certain 

Phosphorescent  substances  and  of  making  air  a  conductor  of  electricity, 
his  property  seems  to  depend  upon  the  presence  of  bodies,  probably 
elements,  which  always  accompany  uranium.  These  elements,  because 
of  their  similarity  to  the  known  elements,  have  been  called  radiolead, 
radiothorium  (=  actinium),  radiobismuth  (=  polonium),  radiobarium 
(=  radium). 

Uranium  oxide,  UO2,  is  obtained  as  a  black  powder  on  heating  the 
higher  uranium  oxides  in  a  current  of  H.  It  is  soluble  in  hydrocliloric 
and  sulphuric  acids,  forming  green  uranous  salts  and  also  soluble  in  nitric 
acid,  producing  uranyl  nitrate.  On  heating  in  the  air  it  is  transformed 
into  uranous-uranic  oxide,  UO2  +  2UO3,  and  colors  glass  or  porcelain  black. 

Uranyl  oxide,  (U02)0,  is  prepared  by  dissolving  uranium  or  uranium 
oxides  in  nitric  acid,  evaporating,  and  heating  the  uranyl  nitrate,  U02(N03)2, 
obtained  to  250°.  On  warming  uranyl  oxide  with  HNO3  it  is  changed 
into  uranylic  acid,  U02(OH)2.  Uranyl  oxide  gives  a  greenish-yellow 
fluorescence  when  fused  with  glass. 

Uranyl  phosphate,  (U02)2HP04  +  3H20,  is  precipitated  from  uranyl 
salts  by  phosphates  as  a  yellowish-white  powder  (quantitative  estimation 
of  phosphoric  acid). 

Uranyl  sulphide,  UO^S,  is  obtained  as  a  black  precipitate  by  treating 
uranyl  salts  with  ammonium  sulphide. 

Uranates.  Those  derived  from  uranylic  acid  are  not  known.  If  a 
solution  of  uranyl  salts  is  treated  with  caustic  alkali,  a  yellow  precipitate 
of  alkali  uranates  is  obtained.  These  are  analogous  in  composition  to 
the  dichromates;  e.g.,  NagUgO^.  Sodium  uranate  is  the  uranium  yellow 
of  commerce. 

IRON  GROUP. 
Manganese.     Iron.     Cobalt.     Nickel. 
These  decompose  water  only  at  higher  temperatures  and  are  precipi- 
tated from  their  solutions  by  HgS  only  in  the  presence  of  bases  (p.  123). 
The  cyanides  of  manganese,  iron,  and  cobalt  form  peculiarly  complicated 
compounds  (see  Cyanogen  and  p.  102). 


MANGANESE.  273 

1.  Divalent"  they  form  compounds  which  are  similar  to  those  of  the 
magnesium  group,  as  well  as  to  the  cupric  compounds,  especially  by  the 
behavior  of  their  sulphates  and  their  carbonates. 

2.  Trivalent  they  form  compounds  which  are  constituted  analogously 
to  those  of  the  aluminium  and  chromium  groups. 

3.  Manganese  and  iron  also  occur  hexavalent,  producing  acids;  man- 
ganese also  tetravalent  and  heptavalent. 

The  six  elements  of  the  platinum  group  as  mentioned  on  p.  55  are 
allied  to  the  metals  of  the  iron  group  with  regard  to  chemical  properties 
and  their  position  in  the  periodic  system. 

I.  Manganese. 

Atomic  weight  55=  Mn. 

Occurrence.  Only  native  in  meteorites;  combined  as  pyrolusite 
or  brownstone  (MnOj),  braunite  (Mn^g),  manganite,  (MnO.OH), 
hausmannite  (MnjOJ,  rhodochrosite  •  (MnCOg),  alabandite  (MnS). 
Traces  of  manganese  are  found  in  many  plants  and  animals. 

Preparation.  By  fusing  manganese  oxides  with  carbon  or  with 
aluminium  (p.  248). 

Properties.  Grajdsh-white,  very  hard,  brittle  metal  of  specific 
gravity  7.5,  melting  at  about  1900°.  It  oxidizes  in  moist  air,  decom- 
poses boihng  water  with  the  generation  of  hydrogen,  dissolves  in 
all  acids,  forming  manganous  salts,  is  not,  unlike  the  other  metals  of 
this  group,  attracted  to  a  magnet,  nor  does  it  become  magnetic. 

Divalent  manganese  forms  the  manganous  compounds,  triva- 
lent manganese  the  manganic  compounds,  the  hexavalent  manga- 
nese the  manganic  acid  compounds,  and  heptavalent  manganese  the 
permanganic  compounds. 

a.  Alloys  of  Manganese. 

Cupro-manganese,  manganese  copper  (30  per  cent.  Mn),is  a  constituent 
of  various  alloys  of  copper  having  great  hardness  and  toughness  (manga- 
nese bronzes);  spiegel-eisen  (10  to  20  per  cent.  Mn)  and  ferro-manganese 
(20  to  70  per  cent.  Mn)  are  of  importance,  as  they  make  varieties  of  iron 
denser  and  tougher.     Manganin,  see  Nickel. 

h.  Manganous  Compounds. 

Manganese  monoxide,  manganous  oxide,  MnO,  is  obtained  by  heating 
manganous  carbonate  in  the  absence  of  air,  or  by  heating  all  oxides  of 
manganese  in  a  current  of  hydrogen.  It  is  a  green  powder  readily  solu- 
ble in  acids,  and  quickly  oxidizes  into  brown  manganous-manganic  oxide, 
MugO^,  in  the  air. 

Manganous  hydroxide,  Mn(0H)2,  is  obtained  by  treating  a  manganous 
salt  solution  with  caustic  alkali,  when  a  white  precipitate  is  formed 
which  quickly  oxidizes  in  the  air  into  brown  manganic  hydroxide. 

Manganous  sulphide,  MnS,  occurs  as  manganese  blende  (alabandite) 
in  black  cubes,  and  is  obtained  by  treating  a  manganous  salt  solution  with 


274  INORGANIC  CHEMISTRY. 

ammonium  sulphide,  which  produces  a  flesh-colored  precipitate  that 
quickly  turns  brown  on  oxidizing  in  the  air. 

Manganous  chloride,  MnCl2  +  4H20,  forms  light-red  crystalline  masses 
which  deliquesce  in  the  air  and  decompose  on  heating.  The  solution 
of  MnClg  obtained  in  the  preparation  of  chlorine  (p.  133)  is  mixed  with 
lime  and  air  blown  through,  when  the  so-called  calcium  manganite, 
CaMnOg,  separates  (p.  275).  This  compound  can  be  used  like  MnOg  in 
the  preparation  of  chlorine :  MnClg  +  2CaO  +  0= CaMnOg  +  CaClg  ( Weldon's 
process). 

Manganous  sulphate,  MnS04,  crystallizes  below  6°  with  7  mol.  of  water 
in  pink  monoclinic  prisms  (isomorphous  with  ferrous  and  cobaltous  sul- 
phate, etc.) ;  at  ordinary  temperatures  it  forms  triclinic  prisms  with  5  mol. 
of  water  (isomorphous  with  cupric  sulphate);  1  mol.  of  water  of  crystal- 
lization is  first  given  off  at  higher  temperatures  than  the  others.  With 
alkali  sulphates  it  forms  double  salts  which  have  an  analogous  constitu- 
tion and  are  isomorphous  with  the  corresponding  magnesium  salts,  etc. 
(p.  229). 

Manganous  carbonate,  MnCOa,  occurs  as  manganese  spath  (rhodro- 
crosite)  in  rose-red  crystals  which  are  isomorphous  with  calc  spar  and  iron 
spar,  etc. 

c.  Manganic  Compounds. 

The  manganic  salts  are  very  unstable  and  are  decomposed  by  water  or 
on  heating. 

Manganic  oxide,  Mn203,  occurs  in  braunite  as  brown  crystals,  and  is 
obtained  as  a  black  powder  by  gently  heating  the  oxides  and  hydroxides 
of  manganese  in  the  air. 

Mangano-manganic  oxide,  Mn304  (mangano-manganite,  see  below), 
occurs  as  hausmannite  and  is  obtained  as  a  reddish-brown  powder  (man- 
ganese brown,  bister)  on  strongly  heating  all  oxides  and  hydroxides  of 
manganese  in  the  air.  Both  of  the  above  oxides  are  decomposed  by  hot 
nitric  acid  into  manganous  nitrate  and  manganese  dioxide: 
Mn  A  +  4HN03=  2Mn(N03)2 + MnO^  +  2H2O ; 
Mn203  +  2HN03=Mn(N03)2  +Mn02  +  H20. 

Cold  sulphuric  acid  dissolves  them,  forming  red  solutions  which  con- 
tain a  mixture  of  manganous  and  manganic  sulphates.  Cold  hydro- 
chloric acid  acts  in  a  similar  manner.  With  hot  sulphuric  acid  and  hydro- 
chloric acid,  on  the  contrary,  they  behave  like  manganese  dioxide  (see 
below). 

Manganic  hydroxide,  Mn(0H)3,  is  obtained  by  allowing  manganous 
hydroxide  to  stand  in  the  air,  producing  a  brownish-black  powder  which 
behaves  towards  acids  like  manganic  oxide.  It  decomposes  readily  into 
metamanganic  hydroxide,  MnO(OH),  which  occurs  as  manganite.  Mix- 
tures of  manganic  hydroxide  with  ferric  and  aluminium  hydroxides  form 
the  colors  umber  and  ocher. 

Manganic  chloride,  MnCls,  has  not  been  isolated.  If  manganic  hydrox- 
ide or  manganic  oxide  is  dissolved  in  hydrochloric  acid,  manganic  chloride 
is  formed,  which  on  warming  immediately  begins  to  decompose  with  the 
generation  of  chlorine  and  the  formation  of  manganous  chloride:  MnCl3= 
MnCl^+Cl. 

Manganic  sulphate,  Mn2(S04)3,  is  obtained  on  carefully  heating  man- 
ganese dioxide  with  concentrated  sulphuric  acid  to  140°,  which  gives  an 


MANGANESE.  275 

amorphous  dark-green  powder  that  at  160°  decomposes  into  2MnS04  + 
SO2  +  O2.  With  alkali  sulphates,  etc.,  it  forms  stable  manganese  alums 
(p.  252).  In  the  air  it  quickly  decomposes  into  manganic  hydroxide, 
but  with  water  much  quicker.  Manganese  alum  is  decomposed  in  the 
same  manner  by  water. 

Manganic  carbonate,  Mug  (003)3,  is  not  known. 

d.  Higher  Manganese  Compounds. 

Manganese  dioxide,  MnOj,  occurs  in  hard  gray  crystals,  as  well 

as  in  soft  fibrous  masses  as  pyrolusite  or  brownstone.     On  strongly 

heating  it  gives  off  part  of  its  oxygen  (p.  107),  and  on  warming  with 

concentrated  sulphuric  acid  it  dissolves  with  the  formation  of  man- 

ganous  sulphate  and  oxygen  is  set  free:    Mn02+H.S04  =  MnS04+ 

H2O+O   (method  of  preparing  oxygen).     It  is  insoluble  in  nitric 

acid  or  dilute  sulphuric  acid.     It  dissolves  in  warm   hydrochloric 

acid  with  the  generation  of  chlorine  and  the  formation  of  manganous 

chloride  (p.  132). 

Manganous  Acids.  MnOg  may  be  considered  as  the  anhydride  of  the 
acids  H2Mn03(Mn02  +  H20),  H4Mn04(Mn02  +  2H20),  H2Mn,05(2Mn02  + 
H2O),  which  are  not  known  free,  but  whose  salts  are  precipitated  by 
oxygen  from  the  manganous  salts  in  the  presence  of  bases.  These  salts 
are  called  manganites:  calcium  manganite,  CaMnOg  (p.  274),  manganous 
manganite,  (Mn2)Mn04  (see  above),  potassium  manganite,  KgMuaOg. 

Manganic  acid,  H2Mn04,  and  manganic  anhydride,  MnOg,  are 
not  known  free. 

Manganates  are  formed  as  dark-green  masses  whenever  a  man- 
ganese compound  is  fused  with  bases,  oxides,  or  carbonates  in  the 
air  (or  in  the  presence  of  salts,  giving  up  oxygen) : 

3Mn02+  6K0H+  KCIO3  =  3K2Mn04+  KCl-h  3H2O. 

Many  manganates,  especially  of  the  alkali  metals,  are  soluble  in 
water;  if  alkaU  hydroxides  are  present,  they  dissolve  unchanged 
with  a  green  color;  others  also  become  red  in  water  or  acids  (even  on 
standing  in  the  air  by  the  CO2  contained  therein),  or  by  chlorine,  due 
to  the  formation  of  permanganates  and  the  separation  of  brown 
MnO.;  e.g.,  3K2Mn04+2H20=2KMn04+Mn02+4KOH  (on  account 
of  this  change  in  color  potassium  manganate  was  formerly  called  the 
"mineral  chameleon").  If  the  green  solution  is  carefully  evaporated, 
we  obtain  the  manganate  in  dark-green  crystals,  of  which  the  alkah 
manganates  are  isomorphous  with  the  alkah  sulphates  and  chromates. 
The  manganates  act  either  directly  as  oxidizing  agent  or  indirectly  by 
their  conversion  into  permanganates. 


276  INORGANIC  CHEMISTRY. 

Manganese  heptoxide,  Mn207,  permanganic  anhydride,  is  obtained 
on  slowly  introducing  potassium  permanganate  into  cold  concen- 
trated sulphuric  acid:  2KMn04+H2804  =  K2S04+Mn20;+H20.  It 
is  a  dark-green  heavy  liquid  which  forms  readily  decomposable  violet 
vapors  and  which  on  heating  decomposes  into  2Mn02+30  with 
explosive  violence,  and  gradually  on  standing.  It  has  energetic 
action  on  paper,  alcohol,  etc.,  inflaming  them  on  contact  therewith. 

Permanganic  Acid,  HMn04.  If  a  barium  permanganate  solution 
is  treated  with  the  necessary  quantity  of  dilute  sulphuric  acid,  a 
deep-red  solution  of  permanganic  acid  is  obtained.  This  latter 
decomposes  even  in  the  light  or  on  warming,  with  the  generation  of 
oxygen:    2HMnO,  =  H20+30+2Mn02. 

Permanganates  are  produced  from  the  manganates  by  the  action 
of  chlorine  or  acids  (see  above),  and  are  obtained  as  dark-violet  crystal 
on  the  evaporation  of  the  respective  solution.  These  crystals  are 
mostly  isomorphous  with  the  corresponding  perchlorates.  The 
permanganates  are  soluble  in  water  or  dilute  acids  without  decom- 
position, and  in  the  presence  of  bases  they  are  converted  into  manga- 
nates: 2KMn04+2KOH-2K2Mn04+H20  +  0.  On  heating  they 
give  off  oxygen,  lOKMnO^  =3K,Mn04-f-7Mn02+2K,0+ 120,  and 
in  solution  they  also  readily  give  off  a  part  of  their  oxygen  to  oxidiza- 
ble  bodies,  and  hence  they  are  powerful  oxidizing  and  disinfecting 
agents.  They  set  chlorine  free  from  hydrochloric  acid,  they  oxidize 
sulphur  dioxide  into  sulphuric  acid,  ferrous  salts  into  ferric  salts, 
oxahc  acid  to  carbon  dioxide,  most  organic  compounds  into  carbon 
dioxide  and  water,  and  with  H2O2  they  give  off  oxygen  (p.  118).  If 
the  oxidation  takes  place  in  the  presence  of  an  acid,  then  colorless 
manganous  salts  are  produced :  2KMn04+  3H2SO4  =  K2SO4+  2MnS04+ 
3H2O+5O;  while  if  the  oxidation  takes  place  in  neutral  or  alkaline 
solution  the  oxides  of  manganese  separate  out:  2KMn04-|- H2O  = 
2Mn02+2KOH+30.  When  dry  they  explode  with  many  oxidiza- 
ble  bodies,  and  with  sulphuric  acid  they  generate  the  readily  explosible 
Mn20,. 

Potassium  permanganate,  KMn04,  is  obtained  by  the  action 
of  carbon  dioxide  upon  potassium  manganate  solutions  (p.  275)  until 
they  have  attained  a  red  color:  3K2Mn04+2C02=2KMn04+MnO  + 
2K2CO3.  On  evaporating  this  liquid  dark-violet  rhombic  prisms  are 
obtained  which  are  soluble  in  16  parts  water. 


k 


IRON.  277 

Calcium  permanganate,  Ca(MnOJ2  is  soluble  in  4  parts  water 
and  hence  its  aqueous  solution  has  a  greater  oxidizing  and  disin- 
fecting power  than  KMn04. 

e.  Detection  of  Manganese  Compounds. 

1.  When  fused  with  borax  in  the  outer  blowpipe  flame  they 
give  an  amethyst-red  bead. 

2.  When  heated  with  soda  and  saltpeter  they  give  a  bluish-green 
mass  of  sodium  manganate. 

3.  Ammonium  sulphide  precipitates  flesh-colored  manganous 
sulphide    (also   from  manganates   and   permanganates) : 

K2Mn04+  4(NHJ2S  =  K,S+  MnS+ 4H2O+  2S+  8NH3. 

3.  Iron  (Ferrum). 

Atomic  weight  55.9=  Fe. 

Occurrence.  Native  only  in  meteoric  iron,  but  combined  in  small 
quantities  in  river-,  sea-,  and  spring-waters,  and  in  large  quantities  in 
many  minerals  which  often  form  extensive  deposits: 

Ferro-ferric  oxide,  Fe3Q4,  as  magnetic  iron  ore. 

Ferric  oxide,  FeJ^.^,  as  red  haematite,  specular  iron  ore;  blood- 
stone ;  with  clay  as  red  clay-ironstone  and  called  itabiryte. 

Ferric  oxide  and  hydroxide,  Fe^03+2Fe(OH)3,  as  brown  haematite 
or  limonite. 

Iron  bisulphide,  FeSj,  when  regular  as  iron  pyrites  and  when 
rhombic  called  marcasite. 

Ferro-ferric  sulphide,  SFeS+Fe^Og,  as  magnetic  pyrites. 

Ferrous  carbonate,  FeCO^,  as  spathic  iron  ore. 

Ferrous  and  ferric  silicates  occur  in  many  minerals  and  in  most 
rocks,  and  reach  the  soil  after  weathering.  Iroji  nitride  is  found 
in  lava. 

Preparation.  Pure  iron  is  not  obtained  by  the  reduction  of  iron 
oxide  with  carbon,  as  this  latter  forms  in  part  a  carbide  with  the 
iron.  It  is  obtained  by  heating  ferric  oxide  or  ferrous  chloride  in  a 
current  of  hydrogen  which  forms  a  gray  powder  that  inflames  spon- 
taneously in  the  air  and  burns  into  ferric  oxide  (iron  p5a-ophorous) . 
If  the  reduction  takes  place  at  higher  temperatures,  it  is  no  longer 
inflammable  (reduced  iron,  ferrum  reductum).  It  is  obtained  in  com- 
pact masses  by  fusing  powdered  iron  in  the  oxyhydrogen  blowpipe 
or  by  fusing  the  purest  wrought  iron  (piano-wire)  with  iron  oxide, 
when  this  iron  oxide  takes  up  all  the  impurities. 


278  INORGANIC  CHEMISTRY. 

Properties.  Crystalline  silver-white  masses  which  melt  at  about 
1800°  and  have  a  specific  gravity  of  7.8.  Iron  is  rather  soft, 
weldable  and  malleable,  is  attracted  by  magnets,  and  is  itself  mag- 
netic, but  loses  its  magnetism  as  soon  as  the  magnet  is  removed. 
It  is  unchangeable  in  dry  air;  in  moist  air  it  is  covered  with  ferric 
hydroxide  (rust) ;  on  heating  in  the  air  it  is  covered  with  black  ferrous- 
ferric  oxide  (forge-scales).  When  finely  powdered  it  decomposes 
water  with  the  evolution  of  hydrogen  at  ordinary  temperatures, 
but  when  compact  this  takes  place  only  at  a  red  heat.  It  dissolves 
in  dilute  acids  with  the  generation  of  hydrogen  and  the  forma- 
tion of  ferrous  salts;  in  concentrated  sulphuric  acid  it  forms  ferric 
sulphate  and  generates  SO^;  in  hot  concentrated  nitric  acid  it  forms 
ferric  nitrate  with  the  generation  of  NO. 

If  iron  is  dipped  in  concentrated  nitric  acid  and  then  washed,  it 
is  not  further  acted  upon  by  nitric  acid  and  does  not  precipitate 
copper  from  the  solutions  of  its  salts  (passivity  of  iron).  In  the 
molten  state  it  can  take  up  5  per  cent,  of  carbon,  which  exists  either 
mechanically  mixed  in  the  form  of  graphite  or  alloyed  with  the  iron 
as  iron  carbide  (FeC4,  FeCj,  FcjCg,  p.  186).  When  finely  powdered 
it  may  also  combine  with  carbon  monoxide  (p.  189). 

Iron  forms  three  series  of  compounds: 

Bivalent  iron  forms  the  ferrous  compounds  whose  salts  are 
white  or  green  and  have  great  similarity  to  those  of  the  magnesium 
group. 

Trivalent  iron  forms  the  ferric  compounds,  which,  in  contradis- 
tinction to  the  corresponding  compounds  of  manganese,  cobalt,  and 
nickel,  are  very  stable  and  behave  like  the  aluminium  and  chromium 
salts.     The  salts  of  this  series  are  brown  or  yellow. 

Hexavalent  iron  forms  ferric  acid,  which,  Hke  manganic  acid,  is 
known  only  in  combination. 

a.  Alloys  of  Iron. 

Pure  iron  has  no  technical  uses,  but  only  as  alloyed^  with  carbon, 
manganese,  chromium,  tungsten,  and  silicon.  Iron  is  classified 
according  to  the  amount  of  carbon  it  contains  and  the  properties  im- 
parted thereby,  as  follows: 

1.  Malleable  iron  contains  0.1  to  1.6  per  cent,  carbon,  is  fused 
with  difficulty,  is  forgeable  and  malleable. 

a.  Steel  contains  0.6  to  1.6  per  cent,  carbon,  is  the  only  form  of 


I 


IRON.  279 

iron  that  can  be  tempered,  is  light  gray  in  color,  granular  and  not 
fibrous,  not  as  tough  as  wrought  iron,  more  easily  melted  (at  about 
1400°),  and  does  not  readily  rust. 

If  melted  steel  is  allowed  to  cool  slowly,  it  becomes  more  pUable 
and  softer  than  crude  iron.  But  if  it  is  quickly  plunged  in  water,  it 
becomes  brittle  and  hard  so  that  it  can  scratch  glass,  and  in  fact 
the  higher  the  temperature  to  which  it  is  heated  and  the  colder  the 
liquid  used  in  cooling  it  the  harder  does  it  become. 

As  the  degree  of  hardness  cannot  be  well  controlled  by  simply  cooling, 
it  is  best  to  heat  the  steel  to  be  hardened  to  a  certain  temperature  and 
then  allow  it  to  cool  slowly.  Polished  steel  on  heating  first  becomes  pale 
yellow,  then  brown,  violet,  pale  blue,  dark  blue,  depending  upon  the  heat 
applied. 

h.  Wrought  iron  contains  less  than  0.5  per  cent,  carbon  and 
melts  at  about  1500°.  It  is  the  softest  of  all  varieties  of  iron.  When 
it  contains  0.3  per  cent,  carbon  or  less  it  has  a  fibrous  fracture,  and 
when  it  contains  more  the  fracture  is  granular.  When  fibrous  it  is 
more  resistant  to  fracture. 

As  forms  of  iron  which  can  be  tempered  can  now  be  prepared 
by  the  addition  of  larger  amounts  of  manganese,  chromium,  tungsten, 
and  siUcon  to  iron  containing  minimum  amounts  of  carbon,  it  is  not 
possible  to  differentiate  between  steel  and  wrought  iron  by  the  amount 
of  carbon  contained  in  them.  Many  intermediary  products  exist 
between  steel  and  wTought  iron,  so  that  it  is  often  impossible  to  tell 
which  is  which.  For  this  reason  malleable  iron  is  classified  accord- 
ing to  its  condition  after  its  preparation. 

2.  Pig  or  cast  iron  (crude  iron)  contains  2.3  to  5  per  cent,  carbon, 
is  hard  and  brittle,  melting  at  about  1100°  and  suddenly  passing 
into  the  liquid  state  without  previously  softening.  For  this  reason 
it  is  riot  forgeable  nor  malleable  when  heated. 

a.  Gray  pig  iron  is  produced  by  slowly  cooling  pig  iron,  when  a 
part  of  the  carbon  contained  therein  separates  out  as  black  plates  of 
graphite  and  gives  the  iron  a  dark-gray  color.  It  is  not  very  hard,  but 
brittle,  and  contracts  uniformly  on  cooling;  hence  it  is  used  as  cast  iron 
in  the  preparation  of  cast-iron  ware. 

6.  White  pig  iron  is  produced  by  quickly  cooling  the  pig  iron,  when 
the  carbon  remains  in  combination  with  the  iron.  From  crude  iron  con- 
taining manganese  we  obtain  on  slowly  cooling  a  variety  of  iron  called 
"  spiegel-eisen."  It  is  very  hard  and  brittle  and  contracts  unevenly  on 
cooling.     It  is  used  in  the  manufacture  of  steel  and  wrought  iron. 


280  INORGANIC  CHEMISTRY, 

Iron  containing  1.6  to  2.3  per  cent,  carbon  is  not  used  for  technical 
purposes.  Pig  iron  is  the  material  from  which  all  other  varieties  of 
iron  are  prepared.  In  its  obtainment  ores  containing  chiefly  iron 
oxide  and  iron  carbonate  are  made  use  of,  and  these  are  reduced  by- 
heating  with  carbon.  Ores  containing  sulphur  are  seldom  used,  as  the 
sulphur  must  first  be  removed  by  roasting  and  converted  into  iron 
oxide. 

1.  Preparation  of  Pig  or  Crude  Iron.  The  ores  are  roasted,  in  order 
to  make  them  more  porous  and  to  form  oxides,  then  mixed  with 
coke  (or  coal)  and  slag-forming  substance  (flux),  and  then  introduced 
into  the  blast-furnace,  which  is  previously  filled  with  red-hot  coals 
(charcoal  was  formerly  used;  anthracite  cannot  be  used  directly, 
but  must  first  be  converted  into  coke).  The  iron  ores  nearly  always 
contain  clay  and  sand,  which  are  both  infusible  and  prevent  the 
coalescence  of  the  melted  particles  of  iron;  hence  substances  (flux) 
are  added  to  the  ore  before  the  iron  melts  which  form  a  readily 
liquefiable  silicate  (slag)  with  the  above  bodies. 

The  flux  consists  of  sand  or  clay  when  the  ores  are  poor  in  silicates, 
and  of  limestone  when  the  ores  are  rich  in  silicates.  The  slag  causes 
the  molten  particles  of  iron  to  conglomerate,  dissolves  the  foreign  con- 
stituents of  the  iron,  and  prevents  the  oxidation  of  the  crude  iron  by  the 
oxygen  of  the  air-blast.  As  the  iron  ores  are  reduced  only  at  very  high 
temperatures,  the  active  combustion  is  maintained  by  a  blast  opening  in 
the  lower  part  of  the  furnace. 

As  fast  as  the  coke  burns  and  the  ore  with  the  flux  melts,  the  material 
sinks  and  is  replaced  from  above  continuously,  so  that  a  blast-furnace 
may  be  in  operation  for  several  years.  The  molten  iron  collects  at  the 
base  of  the  furnace,  and  the  molten  slag  floats  upon  the  iron  and  is  drawn 
off  through  openings  on  the  side.  As  soon  as  the  melted  iron  reaches  the 
slag  apertures  it  is  drawn  off  through  openings  at  the  bottom  and  run 
off  into  sand  moulds. 

In  the  upper  part  of  the  furnace  (heating  zone)  the  material  is  warmed 
and  dried.  In  the  next  part  (the  reduction  zone)  the  iron  oxide  is  reduced 
into  spongy  iron  by  the  carbon  monoxide  produced  in  the  lower  part  of 
the  furnace  by  the  combustion:  Fe203  +  3CO=2Fe+3C02.  In  the  lower 
part  of  the  furnace,  where  the  combustion  is  very  energetic,  due  to  the 
air  introduced  by  the  blast,  the  coke  burns  into  carbon  dioxide,  which  is 
reduced  to  carbon  monoxide  by  passing  through  the  upper  layers  of  red- 
hot  coal:  C02  +  C=2CO. 

The  temperature  of  the  reduction  zone  is  not  sufficient  to  melt  the 
iron;  but  it  sinks  with  the  flux  to  the  lower  and  hotter  part  of  the  furnace 
and  here  combines  with  the  carbon,  forming  readily  fusible  crude  iron 
(carbonization  zone).  The  soft  crude  iron  now  sinks  to  a  still  hotter  part, 
where  it  melts  (fusion  zone),  and  where  the  slag  forms  from  the  flux  and  the 
other  bodies  admixed,  and  which  prevents  the  oxidation  of  the  iron  as  it 


IRON.  281 

passes  the  openings  of  the  air-blast  (combustion  or  oxidation  zone).  The 
iron  collects  below  the  air-blast,  and  the  slag  which  floats  upon  it  prevents 
its  further  oxidation. 

2.  Preparation  of  Wrought  Iron.  a.  In  the  Bessemer  process 
fused  crude  ken  is  introduced  into  a  large  pear-shaped  vessel  (con- 
verter) and  compressed  air  blown  through  the  bottom,  and  the  carbon, 
sihcon,  etc.,  is  completely  burnt  out.  In  this  manner  10  tons  of  pig 
iron  can  be  converted  into  wrought  iron  in  20  minutes.  As  soon 
as  all  the  carbon  has  been  burnt  out  (as  shown  by  the  disappearance 
of  the  green  lines  of  carbon  from  the  spectrum  of  the  flame)  the 
molten,  slag-free  wrought  iron  is  poured  out  by  tipping  the  con- 
verter. 

In  the  Bessemer  process  the  phosphorus  contained  in  many  iron  ores 
is  not  burnt  out,  and  this  makes  the  iron  brittle.  In  order  to  prevent  this 
the  converter  is  lined  with  limestone  containing  some  magnesia,  when  all 
the  phosphorus  is  converted  into  calcium  phosphate  (Thomas-Gilchrist 
process,  basic  process).  This  is  collected  as  Thomas  slag,  which  when 
ground  becomes  a  valuable  fertilizer,  as  it  contains  50  per  cent,  calcium 
phosphate  (Thomas  phosphate,  p.  223). 

b.  Pig  iron  is  melted  on  an  open  hearth  or  on  a  reverberatory  hearth 
and  continuously  stirred  (hence  the  name  "puddle  process")*  and  ex- 
posed to  a  current  of  air.  By  this  means  nearly  all  the  carbon  is  burnt 
into  CO2,  while  the  phosphorus,  sulphur,  and  silicon  which  always  exist 
to  a  slight  extent  in  pig  iron  are  also  burnt  into  oxides,  and  the  sur- 
face of  the  molten  iron  is  also  oxidized;  the  ferric  oxide  produced  forms 
a  slag  with  the  silicon  dioxide.  The  mass,  which  consists  of  pasty  wrought 
iron  and  slag  (the  blooms),  is  hammered  or  rolled  while  white-hot  and 
the  slag  pressed  out. 

3.  Preparation  of  Steel,  a.  By  the  Bessemer  process  (2a),  where 
the  air-blast  is  stopped  when  the  flame  is  highest  (Swedish  method),  or 
by  adding  the  proper  amount  of  pig  iron  to  the  wrought  iron  produced 
in  the  converter  and  allowing  the  air-blast  to  blow  through  this 
mixture  for  a  moment  in  order  to  melt  the  mass  (English  method 
of  preparing  Bessemer  steel). 

h.  Pieces  of  wrought  iron  are  embedded  in  carbon  powder  and  heated 
in  closed  clay  boxes,  when  the  carbon  unites  with  the  iron.  This  cementa- 
tion steel  contains  more  carbon  on  the  outside  than  on  the  inside  and  hence 
is  reforged  or  remelted  (cast  steel). 

c.  By  the  Siemens-Martin  process.  By  melting  pig  and  wrought  iron 
together  in  especially  constructed  furnaces  at  a  very  high  temperature. 

d.  By  puddling  in  a  similar  manner  as  described  under  the  preparation 
of  wrought  iron,  but  the  decarbonization  is  not  allowed  to  progress  so  far 
as  in  wrought  iron. 


282  INORGANIC  CHEMISTRY, 

b.  Ferrous  Compounds. 
Ferrous  oxide,  FeO,  is  obtained  as  a  very  unstable  black  powder 

when  hydrogen  or  CO  is  passed  over  ferric  oxide  heated  to  300°. 

Ferrous  hydroxide,  Fe(0H)2,  obtained  by  precipitating  ferrous 
salt  solutions  with  caustic  alkali,  is  a  light-green  precipitate  which 
quickly  oxidizes  into  brown  ferric  hydroxide  in  the  air. 

Ferrous  sulptiide,  FeS,  is  obtained  by  heating  iron  with  the  proper 
amount  of  sulphur  as  a  bronze-colored  crystalline  mass,  insoluble  in 
water,  which  readily  fuses  and  which  dissolves  in  acids  with  the  gen- 
eration of  HjS:  FeS+2HCl  =  FeCl2+H2S.  If  an  intimate  mixture 
of  iron  and  sulphur  powder  is  moistened  with  water,  a  combination 
takes  place  even  at  ordinary  temperatures.  Ammonium  sulphide 
precipitates  amorphous  black  ferrous  sulphide  from  all  iron  salts; 
ferric  salts  are  first  reduced  to  ferrous  salts  by  this  agent,  and  at  the 
same  time  sulphur  separates: 

2FeCl3+  (NHJ^S  =  2FeCl2+  2NH,C1+  S; 
FeCl24-  (NHJ^S  =  FeS     -1-  2NH4CI. 

In  the  air  at  a  gentle  heat  it  is  oxidized  in  part  into  ferrous  sul- 
phate; with  higher  heat  sulphur  dioxide  and  ferric  oxide  are  pro- 
duced :   2FeS+  70  =  Fe,0,+  280^. 

Ferrous  chloride,  FeCl2  +  4H20,  is  obtained  by  dissolving  iron  in  hydro- 
chloric acid  and  evaporating  in  the  absence  of  air.  It  forms  pale-green 
prisms  which  deliquesce  and  which  cannot  be  obtained  anhydrous  with- 
out decomposition.  Anhydrous  ferrous  chloride  can  be  obtained  as  white, 
fusible,  volatile  plates  on  heating  iron  in  hydrochloric  acid  gas. 

Ferrous  iodide,  Felg.  Powdered  iron  is  placed  in  water  and  the  corre- 
sponding quantity  of  iodine  added,  when  a  greenish  solution  is  obtained 
from  which  on  evaporation  Fel2-I-4H20  separates  out  as  bluish-green 
monoclinic  crystals.  It  oxidizes  in  the  air  into  iron  oxide  and  iodine 
separates;  this  decomposition  is  greatly  retarded  by  the  addition  of 
sugar,  hence  the  druggist  keeps  this  body  in  sugar  or  adds  sugar  to  its 
solution. 

Ferrous  sulphate,  green  vitriol,  FeSO.,4-  7H2O,  is  obtained  pure  by 
dissolving  iron  in  dilute  sulphuric  acid  and  evaporating  the  solution. 
It  forms  pale-green  monoclinic  crystals  which  effloresce  in  dry  air 
(p.  115),  and  in  moist  are  covered  with  brown  basic  ferric  sulphate. 
It  may  be  obtained  as  a  crystalline  powder  by  precipitating  the 
solution  w-ith  alcohol.  Ferrous  sulphate  is  prepared  on  a  large 
scale  by  allowing  roasted  iron  pyrites,  FeS_,  to  he  in  the  air  after 
moistening,  when  it  is  oxidized  into  ferrous  sulphate.    This  is  ex- 


IRON.  283 

tracted  with  water  and  allowed  to  crystallize.  On  roasting  the 
iron  pyrites  one-half  of  the  sulphur  is  eliminated  as  sulphur  dioxide 
and  is  used  in  the  manufacture  of  sulphuric  acid.  Ferrous  sulphate 
is  also  prepared  in  the  obtainment  of  copper  by  the  wet  method 
(p.  234).  It  is  soluble  in  1.8  parts  cold  water,  insoluble  in  alcohol,  and 
•on  heating  in  the  air  it  is  transformed  into  ferric  oxide  (p.  130). 

With  alkali  sulphates  it  forms  isomorphous  double  salts  corresponding 
to  the  magnesium  compounds,  of  which  iron  ammonium  sulphate,  FeSO^  + 
(NH4)2S04  +  6H20,  so-called  Mohr's  salt,  is  characterized  by  its  stability 
in  the  air.  Like  magnesium  sulphate,  ferrous  sulphate  loses  its  seventh 
molecule  of  water  first  at  260°. 

Ferrous  sulphate  (siccum) ,  2FeS04  +  SHgO,  is  obtained  as  a  white  powder 
by  heating  ferrous  sulphate  until  it  has  lost  35  per  cent,  of  its  water  and 
still  contains  15  per  cent. 

Ferrous  phosphate^  FcgCPOJa,  occurs  with  SHgO  as  vivianite,  is  ob- 
tained as  a  white  precipitate,  which  is  insoluble  in  acetic  acid,  but  soluble 
in  other  acids,  by  treating  ferrous  salt  solutions  with  sodium  phosphate. 
It  is  oxidized  in  the  air  and  becomes  grayish  blue. 

Ferrous  carbonate,  FeCOg,  occurs  as  spathic  iron  ore  in  yellowish  crys- 
talline masses  or  in  rhombohedra  (which  are  isomorphous  with  carbonates 
of  calcium,  magnesium,  zinc,  manganese,  as  well  as  with  nickelous  and 
cobaltous  carbonates).  It  is  obtained  by  treating  a  solution  of  ferrous 
salt  with  alkali  carbonate  with  the  exclusion  of  air.  It  is  a  white  pre- 
cipitate which  in  the  air  is  quickly  changed  into  brown  ferric  hydroxide; 
as  the  addition  of  sugar  retards  the  oxidation  for  a  long  time,  a  mixture 
of  ferrous  carbonate  with  sugar  forms  the  official  Ferri  carbonas  sac- 
charatus.  Ferrous  carbonate  is  somewhat  soluble  in  water  containing 
carbon  dioxide  and  occurs  in  what  are  called  chalybeate  waters. 

c.  Ferric  Compounds. 

Ferric  oxide,  FeoOg,  occurs  extensively  in  nature  (p.  277).  It  is 
obtained  as  an  amorphous  reddish-brown  powder,  difficultly  soluble  in 
acids,  by  heating  green  vitriol  (in  the  manufacture  of  fuming  sul- 
phuric acid,  p.  130),  also   from  ferrous  or  ferric  hydroxides. 

Ferric  hydroxide,  Fe(0H)3,  occurs  as  brown  haematite  (p.  277), 
and  is  produced  as  rust  on  exposing  iron  to  moist  air.  It  is  ob- 
tained by  mixing  a  ferric  salt  solution  with  an  excess  of  caustic  alkali 
or  ammonia  carbonate  (p.  284)  which  gives  a  reddish-brown  precipi- 
tate insoluble  in  water  and  readily  soluble  in  acids.  It  may  be  dried 
by  careful  heating,  forming  an  amorphous  granular  mass.  When 
freshly  precipitated  it  serves  as  an  antidote  in  arsenical  poisoning 
(p.  174). 

With  cane-sugar,  C.JJ.22^^.,  it  forms  a  so-called  iron  saccharate, 
2Fe(OH)3+Ci2H220ii  +  7H20,  which  is  readily  soluble  in  water. 


284  INORGANIC  CHEMISTRY. 

Sirupus  ferri  oxydati  is  a  solution  of  iron  saccharate  in  dilute  sugar 
sirup. 

Freshly  precipitated  ferric  hydroxide  dissolves  in  ferric  chloride  with 
the  formation  of  iron  oxychloride,  4Fe(OH)3  +  FeCl3.  A  similar  iron 
oxychloride  solution  may  also  be  obtained  by  the  action  of  HCl  upon 
freshly  precipitated  ferric  hydroxide  in  certain  proportions  (Liquor  ferri 
oxychlorati) .  In  these  solutions  the  chlorine  does  not  exist  as  chlorine 
ions  and  hence  does  not  give  any  precipitate  with  silver  nitrate.  If  this 
solution  is  placed  in  a  dialyzer  (p.  47),  a  colloidal  solution  of  ferric  hy- 
droxide free  from  FeClg  is  obtained  as  a  brown  liquid  (dialyzed  iron  oxide 
solution).  Small  quantities  of  alkalies,  alkali  salts,  or  sulphuric  acid,  as 
well  as  boiling,  precipitate  the  ferric  hydroxide  as  a  red  gelatinous  mass. 

Ferric  sulphide,  FcgSg,  may  be  obtained  by  fusing  iron  together  with 
the  proper  quantity  of  sulphur,  like  the  other  sulphides  of  iron. 

Ferric  chloride,  FeCla,  is  obtained  in  an  anhydrous  form  as  dark- 
green  plates  by  heating  iron  in  chlorine  gas.  It  is  obtained  in  solu- 
tion by  the  action  of  hydrochloric  acid  upon  ferric  hydroxide  or 
upon  iron.  In  the  latter  case  ferrous  chloride  solution  is  obtained 
which  is  oxidized  by  chlorine  or  nitric  acid:  FeCl2+Cl  =  FeCl3; 
3FeCl2+  3HC1+  HNO3  =  3FeCl3+  2H2O+  NO. 

On  the  evaporation  of  this  solution  until  it  has  a  specific  gravity  of 
1.57  it  solidifies,  forming  a  yellow  crystalline  mass,  FeClg  +  GHgO.  On 
further  evaporation  to  a  thick  sirup  reddish-brown  crystals  having  the 
formula  FeClg  +  BHaO  separate  out  on  cooling.  These  salts  are  very 
deliquescent,  and  readily  soluble  in  water,  alcohol,  and  ether. 

Ferric  sulphate,  Fe2(S04)3  +  9H20,  is  obtained  by  the  addition  of 
nitric  acid  to  a  solution  of  ferrous  sulphate  which  has  previously  been 
treated,  with  sulphuric  acid.  On  evaporation  to  sirupy  consistency 
colorless  crystals  are  obtained: 

GFeSO^  +  3H2SO4  +  2HN03=  BFe^CSOJg  +  2N0  +  4H2O. 

Ferric-ammonium  sulphate,  FeCNHJ  (804)2+121120,  ferric  alum, 
ammonium  iron  alum,  forms  amethyst-colored  octahedra  which  are 
soluble  in  water. 

Ferric  carbonate,  Fe2(C03)3,  is  not  known;  if  a  ferric  salt  solution  is 
treated  with  alkali  carbonate,  ferric  hydroxide  is  produced: 

2FeCl3  +  BNaaCOa  +  3H2O = 2Fe  (0H)3  +  6NaCl  +  SCO^. 
d.  Higher  Iron  Compounds. 

Ferric  acid,  HJFeO^,  and  its  anhydride,  FeOg,  like  the  corresponding 
compounds  of  manganese,  are  not  found  in  the  free  state. 

Ferrates,  with  the  exception  of  potassium  ferrate,  KjFeO^,  are  un- 
known. Potassium  ferrate  is  obtained  by  fusing  iron  and  potassium 
nitrate  together:  Fe  +  2KN03  =  K2Fe04  +  2NO.  It  forms  red  prisms 
isomorphous  with  potassium  sulphate  and  chromate  which  are  soluble  in 
water  and  whose  solution  is  decolorized  by  an  excess  of  water,  by  acids, 
or  by  standing  in  the  air: 

2K2Fe04  +  5H20  =4KOH  +  2Fe(OH)3  +  30. 


COBALT.  285 

e.  Detection  of  Iron  Compounds. 

1.  Ammonium  sulphide  precipitates  black  ferrous  sulphide 
from  all  solutions  of  iron  salts.  This  precipitate  is  readily  soluble  in 
acids  (p.  282). 

2.  Potassium  ferrocyanide  produces  with  ferrous  salt  solutions 
a  white  precipitate  which  quickly  changes  to  light  blue.  In  ferric 
salt  solutions  it  immediately  produces  a  deep-blue  precipitate  of 
Prussian  blue  (See  Cyanogen  Compounds). 

3.  Potassium  ferricyanide  produces  immediately  a  deep-blue 
precipitate  called  Turnbull's  blue  with  ferrous  salts.  With  ferric 
salt  it  only  forms  a  reddish-brown  coloration. 

4.  Tannic  acid  (which  see)  produces  no  change  in  ferrous  salt 
solutions,  but  with  ferric  salts  it  immediately  gives  a  bluish-black 
precipitate  (pigment  of  common  ink). 

5.  Potassium  sulphocyanide  (which  see)  produces  no  change 
with  ferrous  salts,  but  with  ferric  salts  it  gives  a  blood-red  colora- 
tion of  soluble  iron  sulphocyanide,  Fe(CNS)3. 

3.  Cobalt. 

Atomic  weight  59= Co. 

Occurrence.     Native  only  in  meteoric  iron;   combined  as  safflorite, 

CoAsj,    cobaltite,   CoS.As,   cobalt    pyrites    or   linnseite,    C0S+C02S3, 

cobalt  bloom  or  erythrite,  Co3(As04)2. 

Preparation.  In  all  cobalt  ores  cobalt  is,  in  part  replaced  by  isomor- 
phous  Ni,  Fe,  Mn.  The  separation  of  these  metals  takes  place  in  a  similar 
manner  as  in  quantitative  analysis.  We  obtain  finally  by  this  method 
cobaltous  oxide,  which  is  mixed  with  flour  into  a  dough,  this  pressed 
into  small  cubes,  dried,  and  heated  to  a  white  heat  in  large  crucibles  sur- 
rounded by  charcoal  powder  (cube  cobalt  of  commerce). 

Properties.  Reddish- white,  ductile,  tough,  shining  metal  having 
a  specific  gravity  of  8.9,  melting  at  about  1800°;  it  is  attracted  to 
a  magnet  and,  like  iron,  is  temporarily  magnetic  and  passive  (p.  278). 
It  does  not  change  in  moist  air;  decomposes  water  at  a  red  heat; 
dissolves  slowly  in  hydrochloric  or  sulphuric  acid,  but  rapidly  in 
nitric  acid,  forming  the  corresponding  cobaltous  salts  and  H  or  NO 
respectively. 

As  divalent  it  forms  the  cobaltous  compounds ;  these  behave  sim- 
ilar to  the  magnesium  compounds  (p.  229)  and  are  very  stable.  The 
salts  of  this  series  are  mostly  red  when  they  contain  water,  and  blue 


286  INORGANIC  CHEMISTRY. 

when  anhydrous,  and  are  isomorphous  with  the  corresponding  ferrous 
compounds. 

As  trivalent,  cobalt  forms  cobaltic  compounds;  only  a  few  simple 
salts  of  this  series  are  known,  but  more  complex  salts  are  known 
(see  below). 

a.  Cohaltous  Compounds. 

Cobaltous  oxide,  CoO,  is  obtained  by  heating  cobaltous  hydroxide  or 
cobaltous  carbonate  in  the  absence  of  air.  It  forms  a  greenish  powder 
which,  on  heating  in  the  air,  forms  cobaltous-cobaltic  oxide. 

Cobaltous  hydroxide,  Co(OH)2.  Caustic  alkalies  precipitate  from 
cobaltous  salt  solutions  blue  basic  cobaltous  salts;  these,  on  boiling,  are 
converted  into  rose-red  cobaltous  hydroxide,  which,  on  standing  in  the  air, 
turns  brown  by  oxidation.  It  also  dissolves  in  an  excess  of  ammonia,  form- 
ing cobaltic-amine  salts  (see  below). 

Cobaltous  sulphide,  CoS,  is  obtained  as  a  black  precipitate,  insoluble 
in  dilute  hydrochloric  acid,  when  a  cobaltous  salt  solution  is  precipitated 
with  ammonium  sulphide. 

Cobaltous  sulphate,  CoSO^  +  THjO,  crystallizes  in  monoclinic  brownish- 
red  prisms  and  behaves  like  the  sulphates  of  the  magnesium  group. 

Cobaltous  chloride,  CoClg  +  GHgO,  forms  red  monoclinic  prisms. 
Writing  with  a  pale-red  solution  of  this  salt  can  be  read  only  after  warm- 
ing, as  the  previously  imperceptible  rose-color  becomes  blue  in  this  opera- 
tion, due  to  the  formation  of  anhydrous  cobaltous  chloride  (sympathetic 
ink,  hygrometers). 

Cobaltous  nitrate,  Co(N03)2,  has  the  color  and  the  properties  of  the 
chloride;  it  is  used  in  blowpipe  analysis. 

Cobaltous  silicate  forms  a  constituent  of  blue  glass.  The  blue  color 
called  smalt  is  potassium -cobaltous  silicate. 

b.  Cobaltic  Compounds. 

Cobaltic  oxide,  cobalt  sesquioxide,  CogOg,  is  obtained  as  a  black  powder 
by  gently  heating  cobaltous  nitrate.  On  stronger  heating  it  is,  like 
cobaltous  oxide,  converted  into  black 

Cobaltous-cobaltic  oxide,  Co304=  (CoO+Co^Og). 

Cobaltic  hydroxide,  Co  (OH),,  is  produced  when  chlorine  is  passed  into 
cobaltous  hydroxide  suspended  in  caustic  alkali.  It  forms  a  brownish- 
black  powder:   Co(OH)2  +  H20+Cl=Co(OH)3  +  HCh 

Cobaltic  salts.  Cobaltic  oxide  and  cobaltic  hydroxide,  on  being  well 
cooled,  dissolve  in  acids  with  a  brownish-yellow  color.  The  cobaltic  salts 
thus  obtained  cannot  be  isolated  because  on  evaporation,  or  on  gently 
warming,  they  decompose  with  the  evolution  of  oxygen  or  chlorine  and 
are  transformed  into  cobaltous  salts,  hence  only  a  few  are  known;  e.g., 
002(804)3+181120,  as  well  as  the  corresponding  alum.  We  also  know  of 
the  cohaltic-amine  salts,  especially  the  deep-red  purjmreo-cobaltic  salts, 
CoCl3(NH3)5,  the  pale-red  roseo-cobaUic  salts,  CoCl3(NH3)5(H20),  the 
brownish  yellow  luteo-cobaltic  salts,  CoCl3(NH3)j,  which  are  precipitated 
by  HCl  from  solutions  of  Co(OH)2  in  NHg  when  they  have  stood  in  the 


NICKEL.  287 

air.  Salts  of  cohaltic-hydrocyanic  acid,  H3Co(CN)8  (known  free),  and  of 
cobaltic-nitrous  acid,  H3Co(N02)6  (not  known  free),  are  also  known.  The 
potassium  salt  of  the  latter,  potassium  cobaltic  nitrite,  K3Co(N02)6,  which 
separates  as  a  yellow  precipitate  when  a  cobaltous  salt  solution  is  treated 
with  acetic  acid  and  potassium  nitrite,  is  used  in  the  separation  of  cobalt 
from  nickel  and  in  the  detection  of  potassium,  and  forms  the  color  called 
cobalt-yellow. 

These  last  compounds  have  complex  ions  instead  of  one  cobalt  ion, 
and  hence  do  not  give  the  following  reactions  for  cobalt. 

c.  Detection  of  Cobalt  Compounds. 

1.  When  fused  with  borax  they  yield  a  beautiful  blue  vitreous  mass. 

2..  Ammonium  sulphide  precipitates  black  cobaltous  sulphide,  which  is 
insoluble  in  dilute  hydrochloric  acid  (all  other  metals,  with  the  exception 
of  nickel,  which  are  precipitable  by  ammonium  sulphide  form  sulphides 
which  are  soluble  in  dilute  hydrochloric  acid). 

3.  Potassium  nitrite  precipitates  yellow  potassium  cobaltic  nitrite 
from  cobaltous  salt  solutions  acidified  with  acetic  acid  (see  above). 

4.  Caustic  alkali  precipitates  blue  basic  cobaltous  salts  (p.  286). 

5.  Ammonia  precipitates  blue  basic  cobaltous  salts,  which  are  soluble 
in  excess  of  ammonia  with  brown  coloration,  gradually  becoming  red; 
cobaltic-amine  salts  are  hereby  produced. 

4.  Nickel. 

Atomic  weight  5S.7=Ni. 
Occurrence.     Native  only  in  meteoric  iron;  combined  as  copper- 
nickel  or  niccolite,  NiAs,  nickel  glance  or  gersdorffite,  NiAsS,  nickel 
pyrites,  NiS,  and  garnierite,  Ni5Si40i3+  IVIggSi^Oig^-  SHjO  and  also  in  the 
cobalt  ores. 

Preparation.  Since  the  discovery  of  garnierite,  nickel  is  nearly  entirely 
obtained  from  this  mineral  by  means  of  the  blast-furnace,  in  the  same  way 
as  iron.  In  all  other  nickel  ores  the  nickel  is  partly  replaced  by  isomor- 
phous  Co,  Fe,  Cu;  the  separation  of  these  metals  takes  place  in  several 
roundabout  ways;  the  nickel  oxide  finally  obtained  is  reduced  similarly  to 
cobaltous  oxide  (see  Cobalt). 

Properties.  Silver-white,  ductile,  tough  metal,  of  specific  gravity 
8.8,  unchangeable  in  the  air,  decomposing  water  at  a  red  heat,  melting 
at  about  1600°,  slowly  dissolved  by  hydrochloric  and  sulphuric  acids, 
and  rapidly  by  nitric  acid  with  the  evolution  of  H  or  NO.  It  is  attracted 
by  a  magnet  and  may,  like  iron,  be  temporarily  magnetic  as  well  as 
passive.  On  account  of  its  silver-like  color  and  stabihty,  it  is  exten- 
sively used  to  cover  other  metals  (nickel  plate).  Like  iron,  it  com- 
bines with  carbon  monoxide  (p.  189).  Nickel  compounds  correspond 
in  their  constitution  and  properties  to  those  of  cobalt,  and  are  obtained 
in  the  same  manner. 


288  INORGANIC  CHEMISTRY. 

a.  Alloys  of  Nickel. 

Alloys  of  nickel,  copper,  and  zinc  are  called  German  silver,  argen- 
tan.  German  and  United  States  nickel  coins  consist  of  25  per  cent, 
nickel  and  75  per  cent,  copper.  Nickel  steel  for  armor-plates  con- 
tains 4-5  per  cent,  nickel. 

Alloys  of  nickel  with  copper  (called  nickelin,  constantan),also  with 
copper  and  manganese  (manganin),  have  low  electrical  conductivity 
and  hence  are  used  for  electrical  resistances. 

6.  Nickelous  Compounds. 

Nickelous  oxide,  NiO,  forms  a  gray  powder  and  is  produced  by  heating 

Nickelous  hydroxide,  Ni(0H)2.  This  is  obtained  from  nickelous  salts 
by  alkali  hydroxide  as  a  green  precipitate,  soluble  in  ammonia  with  blue 
color  and,  contrary  to  Co  (OH) 2,  stable  in  the  air, 

Nickelous  sulphide,  NiS,  is  black  and  behaves  like  CoS. 

Nickelous  salts  when  anhydrous  are  yellow  and  green  when  they  con- 
tain water. 

c.  Nickelic  Compounds. 

Nickelic  hydroxide,  Ni(0H)3,  a  black  powder,  and 

Nickelic  oxide,  NigOg,  forming  black  masses,  are  prepared  like  and 
have  similar  properties  to  the  analogous  cobalt  compounds. 

Nickelic  salts  are  not  known  even  in  solution,  as  nickelic  oxide  as  well 
as  nickelic  hydroxide  is  soluble  in  acids  even  in  the  cold,  forming  nickelous 
salts  and  evolving  oxygen  or  chlorine,  and  hence  acts  like  a  superoxide 
(see  Cobaltic  Salts). 

d.  Detection  of  Nickel  Compounds. 

1.  When  fused  with  borax  they  give  a  dark-red  mass  which  on  cooling 
turns  pale  yellow. 

2.  Caustic  alkali  precipitates  green  nickelous  hydroxide   Ni(0H)2. 

3.  Ammonia  partly  precipitates  green  nickelic  hydroxide,  which  is 
soluble  in  an  excess  of  ammonia  with  blue  color. 

4.  Nickel  salts  behave  like  the  cobalt  salts  towards  anunonium  sul- 
phide; they  are  not  precipitated  by  potassium  nitrite. 

GOLD  AND  PLATINUM  GROUP. 

Gold.     Platinum.     Iridium. 

Osmium.     Palladium.     Rhodium.     Ruthenium. 

These  metals,  with  the  exception  of  palladium  and  osmium,  are  not 
acted  upon  by  nitric  acid  and  are  only  dissolved  by  aqua  regia  or  other 
liquids  containing  chlorine.  They  do  not  decompose  water  even  at 
higher  temperatures,  and  are  precipitated  as  sulphides  from  their  acid 
solutions  by  sulphuretted  hydrogen.  These  sulphides  are  soluble  in  alkali 
sulphide  solutions,  forming  alkali  sulphosalts  (see  p.  176). 

Their  oxides  decompose  on  heating  into  the  metal  and  oxygen  (with 
the  exception  of  ruthenium  and  osmium);  hence  they  are  called  noble 
metals  (p.  200). 


GOLD.  289 

Their  lower  oxides  are  weak  bases;  the  higher  oxides,  with  the  excep- 
tion of  those  of  palladium,  are  acidic  oxides.  Gold  occurs  mono-  and  tri- 
valent. 

The  six  metals  related  to  gold  form  the  platinum  group.     They  are 
all  found  native  and  in  fact  alloyed  with  each  other  in   the  platinum 
ores.      They  have   similarities  to  the  iron  group,  and  those  arranged  in 
columns  in  the  following  table  show  great ^lemical  similarity: 
Manganese.     Iron.  CohsMl  Nickel. 

Ruthenium.  Rhodium.  Palladium. 

Osmium.  Iridium.  Platinum. 

The  metals  of  the  first  group  occur  di-,  tri-,  tetra-,  and  octavalent, 
oxidize  readily  in  the  air,  and  form  when  hexavalent  salts  corresponding 
to  the  unknown  acid  W^qO^.  Manganese  and  ruthenium  also  occur 
heptavalent  in  the  acids  HMnO^  and  HRuO^.  Osmium  and  ruthenium 
form  volatile  tetroxides. 

The  metals  of  the  second  group  occur  di-,  tri-,  and  tetravalent,  and 
are  stable  in  the  air  and  form  when  trivalent  stable  salts  corresponding  to 
the  unknown  acid  H3Co(N02)8,  etc.  They  also  form  complex  amine 
salts  with  NHg  (p.  286). 

The  metals  of  the  third  group  occur  di-  and  tetravalent,  nickel  also 
occurring  as  trivalent,  and  likewise  form  amine  salts  with  NH3. 

The  metals  of  all  three  groups,  as  well  as  gold,  form,  as  cyanides,  com- 
plex compounds  with  alkali  cyanides,  and  also  as  chlorides  with  alkali 
chlorides. 

Ru,  Rh,  Pd,  having  a  specific  gravity  of  11.8  to  12.1,  are  called  the 
light  platinum  metals,  while  Os,  Ir,  Pt,  having  a  specific  gravity  of  21.1  to 
22.4,  are  called  the  heavy  platinum  metals. 

I.  Gold  (Auruiti). 

Atomic  weight  197.2=  Au. 

Occurrence.  Native  or  mixed  with  silver  in  the  crystalline  rocks 
or  in  the  sands  obtained  on  the  weathering  of  the  same.  Nearly  all 
river  sand  contains  small  amounts  of  gold. 

Preparation.  The  sand  or  the  rocks  containing  gold  are  stamped, 
and  then  washed  with  water,  when  all  lighter  particles  are  removed, 
while  the  gold  remains  (gold  washing).  The  sands  may  also  be 
mixed  with  mercury,  with  which  it  forms  an  amalgam,  and  the 
mercury  separated  from  the  dissolved  gold  by  distillation. 

Ores  poor  in  gold,  or  the  ores  after  the  amalgamation  process,  are 
ground  with  a  watery  solution  of  potassium  cyanide  with  an  excess  of  air, 
when  all  the  gold  goes  into  solution  as  potassium  aurocyanide,  KAuCCN)^ 
(p.  290),  and  the  gold  is  separated  from  the  solution  by  the  galvanic  current 
or  by  metallic  zinc.  Or  the  roasted  ore  can  also  be  treated  with  chlorine, 
and  the  dissolved  gold  chloride  precipitated  by  ferrous  sulphate  (process, 
p.  290). 

The  gold  thus  obtained  is  separated  from  the  silver,  which  is  nearly 
always  present,  either  by  boiling  with  nitric  acid  (p.  160),  or  with  con- 
centrated sulphuric  acid,  which  leaves  the  gold  undissolved. 


290  INORGANIC  CHEMISTRY. 

Pure  gold  is  obtained  by  dissolving  the  commercial  metal  in  aqua  regia 
and  treating  the  solution  with  ferrous  sulphate,  which  reduces  the  gold 
chloride  and  precipitates  the  gold  as  a  brown  powder.  This  is  fused  with 
borax  and  saltpeter: 

AuCl3+3FeSO,=  Au  +  Fe2(SOj3  +  FeCla. 

Properties.  Shining,  yellow  metal,  nearly  as  soft  as  lead,  having  a 
specific  gravity  of  19.3,  melting  at  1064°.  It  is  the  most  ductile  of 
all  metals  and  can  be  beaten  into  very  thin  sheets  (gold-leaf)  which 
have  a  green  color  by  transmitted  light.  When  finely  divided,  as 
when  precipitated  from  solution  by  organic  substances  (on  the  skin) 
or  by  fine  silver  (toning  of  photographic  prints),  it  appears  red  or 
bluish  violet.  Neither  oxygen  nor  sulphur  nor  acids  combine  with 
gold  directly,  but  liquids  containing  chlorine  (aqua  regia,  chlorine- 
water)  dissolve  it  readily  with  the  formation  of  auric  chloride,  AuClg) 
potassium  cyanide  in  the  presence  of  oxygen  also  dissolves  gold 
readily,  forming  potassium  aurocyanide: 

2Au+  4KCN+  H,0+  O  =  2KAu(CN)2-l-  2K0H. 

Colloidal  gold,  which  with  water  forms  a  blue  or  purplish-red 
solution,  is  also  known  (pp.  199  and  292).  Gold  may  be  precipitated 
as  a  dark-brown  po\vder  from  solutions  of  its  salts  by  other  metals 
and  many  reducing  agents. 

Gold  forms  compounds  having  a  composition  analogous  to 
those  of  thallium;  thus  as  monovalent  it  forms  aureus  compounds,  as 
trivalent  it  forms  auric  compounds.  Besides  the  haloid  salts  no  simple 
salts  are  known,  but,  on  the  contrary,  a  few  complex  salts. 

a.  Alloys  of  Gold. 
Gold  is  alloyed  with  silver  or  copper,  making  it  harder  and  more 
readily  fusible  without  losing  its  color.  The  amount  of  gold  in  an 
alloy  was  formerly  expressed  in  carats  (pure  gold  =  24  carats) ;  good 
gold  ware  is  14  carats,  i.e.,  it  consists  of  14  parts  gold  and  10  parts 
copper.  At  the  present  time  we  generally  designate  pure  gold  as 
1000,  and  denote  the  amount  of  alloys  in  parts  per  1000.  United 
States  and  German  gold  coins  have  a  fineness  of  j%%%,  i.e.,  contam 
one-tenth  copper. 

b.  Aurous  Compounds. 

Aureus  oxide,  AU2O,  is  obtained  by  the  action  of  alkali  hydroxides 
upon  aurous  chloride,  giving  a  dark-violet  powder  which  decomposes  at 
250°  into  Auj  +  O,  and  by  HCl  into  AuClg  +  Au. 


GOLD.  291 

Aureus  chloride,  AuCl,  is  produced  on  heating  auric  chloride  to  180°, 
and  forms  a  white  powder  decomposing  into  Au+Cl  upon  further  heat- 
ing, and  into  AuClg  +  2Au  on  boiling  with  water. 

c.  Auric  Compounds. 

Auric  oxide,  auric  anhydride,  gold  oxide,  AugOg,  is  produced  from  mag- 
nesium aurate  by  treatment  with  concentrated  nitric  acid:  Mg(Au02)2  + 
2HN03=Mg(N03)2  +  H20  +  Au203.  It  is  a  brown  powder  which  behaves 
like  auric  hydroxide  and  decomposes  at  250°  into  AU2  +  O. 

Auric  hydroxide,  auric  acid,  Au(0H)3,  is  prepared  from  magnesium 
aurate  (see  below)  by  treatment  with  dilute  nitric  acid,  Mg(Au02)2  + 
2HN03  +  2H20  =  Mg(N03)2  +  2Au(OH)3,  giving  a  reddish-brown  powder 
which  decomposes  in  the  light,  with  the  generation  of  oxygen.  It  dis- 
solves in  hydrochloric  acid,  forming  auric  chloride;  it  is  not  attacked  by 
oxyacids,  and  dissolves  in  alkali  hydroxides,  forming  aurates. 

The  aurates  are  derived  from  metauric  acid,  HAUO2,  which  is  not  known 
free.  If  an  auric  chloride  solution  is  gently  warmed  with  magnesium 
oxide,  we  obtain  a  yellow  precipitate  of  magnesium  aurate,  Mg(Au02)2; 
if  auric  chloride  solution  is  treated  with  caustic  potash,  auric  hydroxide 
is  precipitated,  and  this  dissolves  in  an  excess  of  the  caustic  potash,  forming 
potassium  aurate,  KAuOg,  which  on  careful  evaporation  may  be  obtained 
as  yellow  needles:  Au(OH)3  +  KOH=  KAUO2  +  2H2O. 

Auric  chloride,  AuClg,  so-called  brown  gold  chloride,  is  obtained  as  a 
brown  crystalline,  deliquescent  mass  on  heating  powdered  gold  in  chlo- 
rine gas.  If  heated  to  180°,  it  decomposes  into  AuCl  +  Clj,  and  on 
slowly  evaporating  its  watery  solution  it  separates  in  yellow  needles  of 
AUCI3  +  4H2O. 

Hydrochlorauric  acid,  HAuCl^,  so-called  yellow  gold  chloride,  sepa- 
rates with  four  molecules  of  water  in  yellow  crystals  on  the  evaporation 
of  the  solution  obtained  by  dissolving  gold  in  aqua  regia. 

Chloroaurates  are  prepared  by  evaporating  the  mixed  solutions  of 
auric  chloride  and  the  respective  metallic  chloride.  They  form  yellow 
crystals,  e.g.,  sodium  chloroaurate,  NaAuCl^  (gold  salt  of  the  photog- 
rapTier). 

Gold  oxide  ammonia,  AU2O3  +  4NH3,  is  obtained  as  a  yellowish-brown, 
readily  explosive  precipitate  when  a  gold  chloride  solution  is  treated  with 
ammonia. 

Auric  sulphide,  gold  sulphide,  AUgSg,  is  obtained  as  a  black  precipitate 
from  gold  salt  solutions  by  sulphuretted  hydrogen;  it  is  only  soluble  in 
aqua  regia,  and  in  alkali  sulphides  it  dissolves,  forming  sulphoauric  salts 
(p.  176),  which  are  derived  from  sulphoauric  acid,  HgAuSg,  which  is  not 
known  free. 

d.  Detection  of  Gold  Compounds. 

1.  When  fused  with  soda  upon  charcoal  they  yield  golden  ductile  gran- 
ules. 

2.  Zinc,  iron,  copper,  and  many  other  metals,  also  reducing  agents, 
such  as  ferrous  sulphate,  arsenic  trioxide,  sulphur  dioxide,  oxalic  acid,  etc., 

Erecipitate  metallic  gold  as  a  brown  powder  from  gold  solutions.     On  rub- 
ing  this  powder  with  a  hard  object  it  takes  a  metallic  luster. 

3.  Sulphuretted  hydrogen  precipitates  black  auric  sulphide,  readily 
soluble  in  yellow  ammonium  sulphide,  forming  (NH4)3AuSa. 


292  INORGANIC  CHEMISTRY. 

4.  Stannous  chloride  solution  which  contains  some  stannic  chloride 
causes  purple-red  precipitations  m  gold  solution.  This  precipitate  con- 
sists of  tin  hydroxide  and  colloidal  gold,  called  purple  of  Cassius. 

2.  Platinum. 

Atomic  weight  194.8=  Pt. 

Occurrence,  Always  native  and  mixed  with  the  other  platinum  metals 
(p.  289)  in  platinum  ores. 

Preparation.  The  platinum  ores  are  treated  with  aqua  regia.  The 
osmium  and  iridium  remaining  undissolved,  the  solution  obtained  is  evap- 
orated partly  and  treated  with  ammonium  chloride,  when  the  plati- 
num precipitates  as  ammonium  platinic  chloride,  (NHJgPtClg,  mixed 
with  some  ammonium  iridium  chloride  (NH^glrClg.  This  precipitate  is 
heated,  when  the  platinum  containing  iridium  remains  as  a  gray  porous 
mass  (spongy  platinum) ;  this  is  fused  in  the  oxyhydrogen  blowpipe  flame 
and  cast  in  moulds.  The  solution  obtained  on  the  filtration  of  the  ammo- 
nium-platinic  chloride  contains  the  chlorides  of  palladium,  rhodium,  ruthe- 
nium, and  a  part  of  the  iridium,  which  can  be  precipitated  by  means  of 
iron  and  separated  according  to  different  methods. 

Properties.  White  soft  metal  having  a  specific  gravity  of  21.4, 
fusible  only  at  1770°,  malleable  at  white  heat,  soluble  only  in  aqua 
regia,  and  not  directly  oxidizable  by  any  oxidizing  agent;  hence 
platinum  vessels  are  extensively  used  in  chemical  manipulations. 
As  platiniun  has  the  same  expansion  coefficient  as  glass,  platinum 
wire  is  used  to  conduct  electricity  into  vacuous  glass  vessels  (incan- 
descent electric  lamps). 

Platinum  is  attacked  on  fusing  with  hydroxides,  sulphides,  nitrates,  and 
cyanides  of  the  alkalies;  it  forms  readily  fusible  alloys  with  phosphorus, 
arsenic,  antimony,  boron,  silicon,  and  most  metals,  so  that  these  metals 
and  very  readily  reducible  compounds  must  not  be  heated  in  platinum 
vessels.  On  heating  with  carbon  or  silicates,  platinum  takes  up  carbon  and 
silicon,  becomes  brittle,  and  hence  platinum  vessels  must  not  be  heated 
on  a  coal  fire  or  over  a  smoky  flame. 

Platinum  may  be  obtained  in  a  finely  divided  state  as  a  black 
powder  (platinum  black)  by  precipitating  it  from  its  solution  by 
zinc  or  iron,  or  by  heating  its  solution  with  caustic  alkah  and  organic 
reducing  substances,  such  as  glucose,  alcohol,  and  glycerine. 

Colloidal  platinum,  which  gives  a  deep-black  solution  in  water,  is 
obtained  when  the  electric  arc  plays  between  platinum  wires  under  water 
(p.  53),  and  may  be  precipitated  from  this  solution  by  salts. 

Platinum  when  finely  divided  has  strong  catalytic  properties  (p.  66), 
especially  accelerating  the  union  of  many  gases  (p.  105).  This  seems  to 
be  brought  about  by  the  property  of  platinum,  especially  when  finely 
divided,  of  condensing  (absorption,  p.  49)  oxygen  and  more  partic- 
ularly hydrogen,  so  that  these  gases,  even  at  ordinary  temperatures,  bring 
about  chemical  changes  which  otherwise  require  higher  temperatures. 


PLATINUM.  293 

Platinum  occurs  divalent  in  the  platinous  compounds  and  tetravalent 
in  the  platinic  compounds. 

a.  Alloys  of  Platinum. 

Platinum  alloyed  with  2  to  3  per  cent,  iridium  is  ordinarily  used, 

as  it  is  harder  and  more  resistant  to  chemicals. 

h.  Platinous  Compounds. 

Platinous  oxide,  PtO,  is  obtained  as  a  gray  powder  on  carefully  heat- 
ing Pt(OH),. 

Platinous  hydroxide,  Pt(0H)2,  is  obtained  as  a  black  powder  on 
warming  PtCl2  with  caustic  alkali.  Both  of  these  compounds  dissolve  in 
bases  and  acids  with  the  formation  of  salts. 

Platinous  chloride,  PtClg,  produced  on  heating  hydrochlorplatinic 
acid  to  280°,  is  a  green  powder,  insoluble  in  water,  which  readily  forms 
soluble  double  salts  with  the  alkali  chlorides,  NaaPtCl^,  which  are  derived 
from 

Hydrochlorplatinous  acid,  HgPtCl^,  which  is  obtained  on  evaporating 
PtCla  with  HCl.     It  forms  yellow  crystals. 

Platosamines  is  the  name  given  to  the  compounds  of  platinous  salts 
with  ammonia;  e.g.,  PtClgCNHg),  PtClgCNHg)^,  PtgClaCNHg),  etc.,  in  which, 
in  place  of  one  platinum  ion,  a  complex  ion  with  one  or  two  divalent  plati- 
num atoms  exists  (p.  84). 

c.  Platinic  Compounds, 

Platinic  oxide,  PtOg,  produced  as  a  black  powder  on  heating  Pt(OH)^, 
and  behaves  like  this  towards  acids  and  bases. 

Platinic  hydroxide,  Pt(OH)^,  platinic  acid,  precipitates  as  a  reddish- 
brown  powder  by  treating  a  solution  of  platinic  chloride  with  caustic 
alkah.  It  dissolves  in  an  excess  of  caustic  alkali,  forming  potassium  plat- 
inate;  e.g.,  Pt(OH),  +  4KOH=K4Pt04  +  4H20.  It  dissolves  in  acids, 
forming  the  corresponding  platinic  salts;    e.g.,  Pt(S04)2. 

Platinates  are  also  produced  on  fusing  platinum  with  alkali  hydroxides. 

Platinic  chloride,  PtCl^,  is  produced  by  the  action  of  chlorine  upon 
platinum  at  very  high  temperatures  and  hence  is  better  obtained  by  heating 
HgPtClg  in  a  current  of  chlorine.  It  forms  reddish-brown  crystalline 
masses  which  readily  dissolve  by  water.  On  the  evaporation  of  its  watery 
solution  PtCl^-t-SHaO  separates  in  yellow  prisms. 

Hydrochlorplatinic  acid,  HaPtClg  +  6H2O,  platinum  chloride  of  com- 
merce, is  obtained  as  red,  deliquescent  crystals  by  evaporating  a  solution 
of  platinum  in  aqua  regia. 

Chloroplatinates.  Those  of  potassium,  ammonium,  calcium,  rubidium, 
as  well  as  numerous  organic  bases,  are  difficultly  soluble  in  water,  hence 
HgPtClg  is  used  in  chemical  analysis. 

Platinic  sulphide,  PtSg,  is  obtained  as  a  black  precipitate,  insoluble 
in  all  acids,  with  the  exception  of  aqua  regia,  by  passing  H2S  into  platinic 
salt  solutions;  alkali  sulphides  dissolve  it  slowly  with  the  formation  of 
sulphoplatinic  salts  Cp-  176),  which  are  derived  from 

Sulphoplatinic  acids,  H^PtgSg  and  HaPtS^,  which  can  be  separated  from 
the  corresponding  sulpho  salts. 

Platinamines  are  the  compounds  of  platinic  salts  with  ammonia,  e.g,, 


294  INORGANIC  CHEMISTRY. 

PtCl^CNHs),  PtCl^CNHg)^,  etc.,  and  which  have  a  constitution  analogous 
to  that  of  the  cobaltic-amine  salts  (p.  286). 

d.  Detection  of  Platinum  Compounds. 

1.  When  fused  with  soda  on  charcoal  they  yield  gray  porous  platinum 
(spongy  platinum)  without  incrustation. 

2.  Sulphuretted  hydrogen  precipitates  black  platinic  or  platinous  sul- 
phide from  its  solution.  On  the  addition  of  ammonium  chloride  or  potas- 
sium chloride  to  its  solution  in  aqua  regia,  the  corresponding  hydrochlor- 
platinic  acid  salt  is  precipitated  (p.  208),  or  finely  divided  platinum  is 
precipitated  from  its  solutions  by  metallic  zinc. 

3.  Palladium. 

Atomic  weight  106.5=  Pd. 
This  metal  occurs  only  native  and  in  the  platinum  ores  (preparation, 
p.  292).  It  is  white,  has  a  specific  gravity  of  11.9,  and  melts  at  about 
1500°  ;|  when  finely  divided  as  so-called  palladium  black  it  dissolves  on 
boiling  with  concentrated  hydrochloric  acid,  sulphuric  acid,  or  nitric  acid. 
It  has  the  property,  especially  when  finely  divided,  of  absorbing  hydrogen, 
even  980  times  its  volume,  with  the  formation  of  a  solid  solution  (p.  65) 
which  appears  like  palladium  and  has  an  energetic  reducing  power  like 
nascent  hydrogen.  Palladium  occurs  divalent  in  the  stable  palladous 
compounds  and  tetravalent  in  the  less  stable  palladic  compounds;  e.g., 
PdCl,. 

Compounds  of  Palladium. 

Palladous  iodide,  Pdig,  is  precipitated  from  solutions  of  iodides  by 
palladium  salts  as  a  black  powder,  and  is  used  in  the  quantitative  estima- 
tion of  iodine  in  the  presence  of  chlorine  and  bromine. 

Palladous  chloride,  PdCla,  forms  brown  masses. 

Palladic  chloride,  PdCl^,  is  known  only  in  solution;  from  both  of  these 
alkali  chlorides  precipitate  the  salts  of  hydrochlorpalladous  acid,  HgPdCl^, 
and  hydrochlorpaUadic  acid,  HaPdClg,  which  are  not  known  free. 

4.  Iridium.  5.  Rhodium.  6.  Ruthenium. 

Atomic  weight  Atomic  weight  Atomic  weight 

193 =Ir.  103 =Rh.  101.7= Ru. 

These  metals  occur  only  native  in  the  platinum  ores  (preparation,  p. 
292),  are  insoluble  when  pure  in  acids  and  aqua  regia,  but  when  alloyed 
with  platinum  are  partly  soluble.  IrClg,  RhClg,  RuClg,  are  formed  by 
heating  the  respective  metal  in  a  current  of  chlorine;  these  give  crys- 
talline, rather  soluble  complex  salts  with  2  mols.  of  alkali  chlorides: 
KaRuClg,  NaglrClg,  (NH4)2RhCl5.  On  dissolving  Ru  and  Ir  in  aqua  regia 
RuCl^  and  IrCl^  are  formed,  which  with  2  mols.  of  alkali  chlorides  yield 
rather  soluble  compounds  which  are  isomorphous  with  the  corresponding 
platinum  salts;  e.g.,  K^RuClg,  (NH4)2lrClg.  RhCl2  and  RhCl^  are  not 
Known;   on  the  other  hand  RhClg  is  found. 

Iridium  is  light  gray,  ductile,  has  a  specific  gravity  of  22.4,  and  melts 
at  1950°.     Its  name  is  derived  from  the  various  colors  of  its  compounds. 

Rhodium  is  light  gray,  ductile,  has  a  specific  gravity  of  12.1  and  melts 
at  about  1860°.  Its  name  is  derived  from  its  red  double  chlorides  {fiodoeii, 
rose-red). 


OSMIUM.  295 

Ruthenium  is  steel-gray,  hard,  and  brittle,  has  a  specific  gravity  of 
12.3,  and  melts  at  about  2000°. 

7.  Osmium. 

Atomic  weight  191  =  0s. 

This  metal  occurs  only  native  in  platinum  ores  (preparation,  p.  292), 
is  steel-gray,  hard,  and  heaviest  of  all  boaies,  specific  gravity  22.5,  and 
melts  at  about  2500°.  On  account  of  its  inlusibility  osmium  is  used 
instead  of  the  carbon  fi.ament  in  incandebcent  electric  light  (Auer's 
osmium  lamp).  When  finely  divided  it  is  oxidized  into  osmium  tetrox- 
ide  on  healing  to  a  red  heat,  as  well  as  by  nitric  acid  or  aqua  regia.  Com- 
pact osmium  is  insoluble  in  acids  and  aqua  regia;  alloys  of  osmium  and 
iridium  as  found  in  platinum  ores  are  likewise  insoluble  therein. 

Compounds  of  Osmium. 

Osmium  tetroxide,  perosmic  anhydride,  ObO^  (preparation,  see  above), 
forms  colorless  prisms  melting  at  about  100°  and  subliming  at  a  some- 
what higher  temperature  and  is  readily  soluble  in  water.  Its  odor  is 
disagreeably  pungent  (oS/U?/,  odor),  its  vapors  attack  the  eyes  and  respira- 
tory organs  violently;  it  is  used  in  histology  as  osmic  acid  or  perosmic 
acid  in  order  to  harden  as  well  as  to  stain  various  tissues,  as  organic 
and  other  reducing  bodies  separate  finely  divided  metallic  osmium  from 
its  solution. 

Osmic  acid,  HgOsO^,  is  precipitated  from  potassium  osmate  by  dilute 
inorganic  acids  sa  a  black  porous  powder. 

Potassium  osmate,  K2OSO4  +  2H2O,  forms  red  octahedra,  and  is  pro- 
duced by  fusnig  osmium  with  KOH  +  KNO3. 

Osmium  chlorides,  OsClg,  OsClg,  OsCl^,  are  produced  on  heating  osmium 
in  a  current  of  chlorine,  and  form  double  salts  with  alkali  chlorides  which 
are  analogous  to  the  ruthenium  compounds;   e.g.,  NagOsClg. 


PART  THIED. 

ORGANIC   CHEMISTRY,  OR  CHEMISTRY  OF  THE 
CARBON  COMPOUNDS. 


CONSTITUTION. 


The  number  of  known  carbon  compounds  is  much  greater  than 
the  compounds  of  all  the  other  elements  together,  and  new  organic 
compounds  are  being  continually  prepared  artificially. 

The  number  of  atoms  which  form  the  molecule  of  an  organic 
compound  is  as  a  rule  very  much  larger  than  in  inorganic  compounds; 
thus,  for  example,  cane-sugar,  CjjHjaOn,  contains  45  atoms  and 
stearin,  03115(0,8113502)3,  173  atoms. 

This  multiplicity  and  complexity  of  organic  compounds  can  be 
explained  (see  Isomerism,  p.  300)  by  the  fact  that  the  0  atoms  are 
tetravalent  and  have  the  power  of  uniting  with  each  other  by  means 
of  one  of  the  bonds  to  a  much  higher  degree  than  the  atoms  of  any 
other  element.  This  bondage  can  also  take  place  in  a  great  many 
different  ways. 

Carbon  is  a  tetravalent  element  and  exists  in  its  simplest  com- 
pound (with  the  exception  of   CO)  with  all  four  valences  satisfied, 

I        II       II 
e.g.,  CH4,  CO2,  CSj)    these  four  bonds  (affinities,  valences,,  p.  28)  of 
carbon  are  alike  in  behavior. 

When  tetravalent  carbon  atoms  combine  together,  then  in  the 
simplest  case  one  bond  of  one  atom  saturates  one  bond  of  the  other 
atom.  Thus  if  two  carbon  atoms  combine  in  this  way,  then  two  of 
the  eight  bonds  are  necessary  for  the  union  of  the  0  atoms;  if  three 
carbon  atoms  combine,  then  four  of  the  twelve  valences  are  necessary 

296 


CONSTITUTION.  297 

for  the  mutual  union;  if  four  carbon  atoms  combine,  then  six  bonds 
are  necessary  for  the  mutual  union,  etc.    Thus: 

Each  new  carbon  atom  introduced  therefore  contains  only  two 
free  bonds  to  which  other  atoms  or  groups  of  atoms,  depending 
upon  their  valence,  can  be  united.  If  we  consider  these  valences 
satisfied,  for  instance,  with  hydrogen,  then  we  obtain  the  compounds 
CH„  C,He,  C3H8,  C,H,o,  etc.,  or  CH„  H3C-CH3,  H3C-CHrCH3, 
CH3"CH2"CH2~CH3,  etc.  Each  of  these  hydrocarbons  (as  well 
as  their  derivatives)  differs  from  the  previous  one  by  CHj  and  hence  we 
can  represent  this  series  by  the  general  formula  CnH;,n+2,  where  N  can 
represent  each  full  number;  e.g.,  C30H62. 

None  of  these  combinations  can  take  up  more  atoms  or  groups 
of  atoms  than  are  represented  by  the  formula  CnHsn+z,  because  the 
remaining  valences  of  the  C  atoms  are  necessary  for  the  mutual 
union;  hence  all  combinations  which  contain  C  atoms  which  are  united 
together  with  one  bond  each,  are  called  saturated  compounds. 

Besides  saturated  compounds  we  know  of  others  which  contain 
C  atoms  united  together  by  more  than  one  valence.  The  individual 
hydrocarbons  of  these  series  (as  well  as  their  derivatives)  differ  also 
from  one  another  by  CHj;  e.g., 

CHrCH^.        CH2=CH-CH3.        CH2=CH-CH2-CH3. 
CH^CH.  CH^C-CHg.  CH^C-CH^-CHg. 

The  compounds  C2H4,  C3H6,  C4H8,  etc.,  correspond  to  the  general 
formula  CnHjn,  the  compounds  C2H2,  C3H4,  CJi^,  etc.,  to  the  general 
formual  CnH;jn-2,  where  n  represents  a  full  number  from  2  on. 

The  union  of  the  C  atoms  by  several  bonds  does  not  denote 
a  firmer  mutual  union  of  these  atoms,  as  such  combinations  are  in  fact 
much  more  readily  split  than  those  where  the  C  atoms  are  simply 
united. 

Compounds  with  multiple-united  C  atoms  can  be  converted  into 
compounds  having  the  C  atoms  in  simple  union;  thus  the  compounds 
having  the  formula  CnHzn  and  CnH2n-2  can  be  converted  into  com- 
pounds having  the  formula  CnH2n+2  by  the  action  of  hydrogen.  In 
these  cases  the  C  atoms  with  double  and  treble  bonds  are  changed 
to  simple  bonds. 


298  ORGANIC  CHEMISTRY. 

Besides  these  unsaturated  compounds  a  still  larger  group  of  C 
compounds  (p.  327)  are  known  which  contain  fewer  hydrogen  atoms, 
etc.,  in  the  molecule  than  the  saturated  compounds,  but  which  still 
behave  like  saturated  ones  in  that  they  are  not  converted  into  satu- 
rated compounds  having  the  formula  CnH2n+2  by  the  addition  of 
atoms  or  groups  of  atoms,  as,  for  instance,  by  H  atoms.  This  devia- 
tion is  to  be  explained  by  the  fact  that  in  these  compounds  the  C 
atoms  do  not  form  an  open  chain,  but  rather  a  ring-formed  closed 
chain  (a  carbon  ring  or  nucleus),  i.e.,  the  beginning  and  end  member 
of  the  chain  are  united  together  (see  below.  Figs.  3,  4). 

In  the  formation  of  carbon  chains  and  carbon  rings  other  multi- 
valent atoms  may  take  part  besides  the  C  atoms  (see  below,  Figs.  1,  2, 
5,  and  6). 

c=      c=         c  c  c  o 

L    h-  =A.=  _/V  -/V   -A- 
i      i     4  i=  4  L  4J-   J  j- 

C=         C=  C  C  N  N 

II  I  I 

Fig.  1.         Fig.  2.  Fig  3.  Fig.  4.  Fig.  5.  Fig.  6. 

Open  chains  which  contain  only  C  atoms  are  called  homocatenic, 
while  those  containing  other  atoms  besides  C  atoms  are  called  hetero- 
catenic.  Closed  chains  which  contain  only  C  atoms  are  called  homO' 
cyclic,  while  those  containing  other  atoms  are  called  heterocyclic^ 
and  the  compounds  of  such  chains  and  rings  have  the  corresponding 
name. 

We  also  know  of  C  compounds  having  several  atomic  rings  which 
are  united  together  directly  or  by  means  of  C  or  other  atoms.  They 
contain  condensed  atomic  rings,  that  is,  atomic  rings  which  belong 
to  several  atoms: 

~     h      h  h  ^  <i   i 

__c    c-c    c—     — c    c— N=:N— c    c—     —dec— 

4  U  (L    4  ^-     4  ,!-    4  ^  <L 

Y  Y        Y         Y        YY 
II  I  I  II. 

Chain  ring.  Condensed  ring. 


SUBSTITUTION.  299 

All  series  whose  individual  members  always  increase  by  CH^  are 
called  homologous  and  isologous  series: 

CH4,  CjHe,  CgHg,  C4H10,  C5H12,  etc. 

C2H4,  CjHe,  C4H8,  C5H10,  etc. 

^2^2;  C3H4,  C4H6,  CsHg,  etc. 

Combinations  belonging  to  a  homologous  series  nearly  always  have 
analogous  properties,  so  that  the  study  of  a  single  member  is  generally 
sufficient  for  the  determination  of  the  properties  of  the  entire  series. 

SUBSTITUTION. 

If  one  or  more  atoms  in  an  organic  compound  be  replaced  (sub- 
stituted) by  one  or  more  atoms  of  corresponding  valence,  we  obtain 
derivatives  of  the  compound;  thus  one  or  more  and  even  in  some 
cases  all  the  hydrogen  atoms  in  a  hydrocarbon  can  be  replaced  by 
other  elementary  atoms  or  by  groups  of  atoms.  Every  hydrocarbon 
thus  forms  the  starting-point  for  a  series  of  compounds  which  all 
contain  the  same  number  of  carbon  atoms.  The  following  substitu- 
tions are  of  general  interest: 

1.  One  hydrogen  atom  can  be  replaced  by  another  univalent  atom 
or  by  a  univalent  group  of  atoms;  thus  from  CH4  we  obtain 

CH3-OH,     CH3-CI,     CH3-NH2,    CH3-CH3. 

2.  Two  hydrogen  atoms  can  be  replaced  by  two  univalent  atoms  or 
one  bivalent  atom  or  group  of  atoms;  thus  from  CH4  we  obtain 

CH2=Cl2,    CH2=(OH)2,    CH2=0,     CH2=NH,    CH^-CH^. 

3.  Three  hydrogen  atoms  can  be  replaced  by  three  univalent, 
one  trivalent,  or  one  bivalent  and  one  univalent  atom  or  group  of 
atoms;  thus  from  CH4  we  obtain 

CH^Clj,    CH^N,    CH^CH,    CH^^' 

4.  Finally,  all  four  hydrogen  atoms  can  be  replaced  by  imi-,  bi-,  etc., 
atoms  or  groups  of  atoms ;  thus  from  CH4  we  obtain 

C^Cl4,    C-O2,     N-C-a,     CF(CH3)4. 

When  uni-,  bi-  and  trivalent  hydrocarbon  radicals  such  as  "CH,, 
"CHj,  -CH  are  substituted  in  place  of  the  hydrogen  atoms  in  CH4, 


300  ORGANIC  CHEMISTRY. 

we  obtain  saturated  and  unsaturated  hydrocarbons  which  are  richer 
in  carbon  and  in  which  substitutions  can  take  place  as  in  CH4;  e.g., 


CH3 

CH3 

CH3 

CH3 

CH, 

:5H, 

CH3 

CH3 

CH, 

CH, 

CH, 

l^H. 

1 

Jh 

in 

k 

CH3 

CH3 

Organic  chemistry  can  therefore  be  defined  as  the  chemistry  of 
the  hydrocarbons  and  their  derivatives.  The  international  nomencla- 
ture given  on  p.  337  depends  upon  the  derivation  of  all  organic 
compounds  from  the  hydrocarbons  having  an  equal  number  of 
C  atoms. 

ISOMERISM. 

The  number  of  C  compounds  is  considerably  increased  by  the 
existence  of  numerous  isomeric  compounds  (pp.  30,  80),  i.e.,  those 
which  have  the  same  qualitative  and  quantitative  composition  but 
different  properties. 

Isomerism  (^cro?,  equal,  /iepo<;,  part)  of  C  compounds  is  to  be 
explained  either  by  the  fact  that  the  molecular  weights  of  the  respective 
compounds  are  multiples  of  each  other  (see  under  1),  or  by  the  fact 
that  the  atoms  constituting  the  molecule  have  a  different  arrange- 
ment in  the  molecule  (see  under  2  and  3). 

On  the  other  hand  many  chemical  compounds  behave  in  such  a  man- 
ner that  two  different  structural  formulae  may  be  ascribed  to  them;  thus 
hydrocyanic  acid  reacts  according  to  the  formula  N=C~H  and  also  ac- 
cording to  the  formula  C  =  N-H.  That  property  of  a  compound  which 
causes  it  so  to  behave  that  two  different^  structural  formulae  can  be 
ascribed  to  it  is  called  tautomerism  (ravro,  same),  pseudomerism,  or 
desmotropism.  It  is  due  to  the  presence  of  a  mixture  of  two  structural 
isomers  which  are  undergoing  continuous  transformations  from  one  into 
the  other. 

I.  General  Isomerism, 

generally  called  polymerism,  is  conditioned  upon  differing  molecular 
weights  of  the  compounds.  We  call  all  compounds  having  unlike 
chemical  and  physical  properties,  the  same  elementary  and  percentage 
composition,  but  different  molecular  weights,  polymers;  thus, 


SPECIFIC  ISOMERISM,  301 

CH,0,  C2H4O2,  CgHgOg,  CfiHjaOe, 

Formalaehyde.        Acetic  acid.  Lactic  acid.  Dextrose. 

^2114,  CgHg,  C4H8,  C5H10, 

Ethylene.  Propylene.  Butylene.  Pentylene. 

2.  Specific  Isomerism, 

generally  called  isomerism  simply,  and  less  often  metamerism,  is 
produced  by  a  different  intramolecular  arrangement  of  the  atoms 
although  the  molecule  has  the  same  size.  Compounds  having  unlike 
chemical  and  physical  properties  but  the  same  percentage  and  ele- 
mentary composition  and  the  same  molecular  weight  are  called  isomers. 

The  atoms  form  in  a  certain  sense  the  building-stones  from  which  the 
structure  of  the  molecules  is  erected.  As  it  is  possible  to  build  two 
entirely  different  structures  from  the  same  number  of  stones,  so  it 
follows  that  the  varying  arrangement  of  the  atoms  in  the  molecule  may 
account  for  the  existence  of  compounds  which  consist  of  the  same  num- 
ber of  atoms  of  the  same  elements  but  having  unlike  chemical  and 
physical  properties. 

This  isomerism  of  the  C  compounds  (with  the  exception  of  stereo- 
isomerism, p.  302)  can  only  be  explained  by  the  fact  that  the  C  atoms 
are  arranged  in  the  molecule  in  different  relative  positions;  thus  in 
the  following  compounds,  which  are  derived  from  CH4  by  the  intro- 
duction of  the  univalent  radical  "CHg,  no  different  arrangement  of 
the  C  atoms  is  possible:    CH3~CH3,   CH3~CH2-CH3. 

If  the  univalent  radical  CH3  is  again  introduced,  we  obtain  the 
hydrocarbon  C4Hio.  The  substitution  may  take  place  in  several 
ways,  either  at  the  C  atom  which  lies  at  the  ends  of  the  chain,  or  at 
the  middle  C  atom;  thus  we  obtain  two  compounds  C4H10: 

In  the  next  member,  C5H12,  three  cases  are  possible: 

CH,-CH-CH2~CH2~CH3  CH3        CH, 


C 
cJg'J)CH-CHrCH,  CH3        CH 

With  the  higher  members  of  this  hydrocarbon  series  (CnHsn+z)  the 
number  of  possible  isomers  increases  very  rapidly  according  to  the  law 
of  permutations: 

Nuniber  of  C  atoms 6 

Possible  number  of  hydrocarbons. .  .   5 


7  8   9  10 

11 

12 

13 

9  18  35  75 

159 

355 

802 

302  ORGANIC  CHEMISTRY. 

Hydrocarbons  having  continuous  carbon  chains  without  branches  are 
called  normal  hydrocarbons. 

Isomers  which  depend  upon  differing  arrangement  of  the  C  chain  are 
also  called  chain  isomers. 

As  we  can  obtain  isomeric  combinations  by  the  introduction  of 
the  univalent  CH3  group  in  different  positions,  so  we  can  obtain  the 
same  by  the  introduction  of  other  atoms  or  groups  of  atoms.  In 
compounds  Hke  CH3CI,  CH2CI2,  CHCI3,  only  one  formation  is  possible 
(see  Stereoisomerism),  also  in  CH2C1~CH3.  In  compounds  like 
C2H4CI2,  €2114(011)2,  etc.,  two  arrangements  of  the  atoms  are  possible, 
as  follows: 

CHg-CHQa  CH2Cl-CH2a. 

CH3CH(OH)2  CH2(OH)-CH2(OH). 

In  the   next   hydrocarbon,   CH3~CH2~CH3,   two   different   com- 
pounds are  possible  by  the  substitution  of  a  chlorine  atom,  namely, 
CH3-CH2-CH2CI  CH3-CHCI-CH3. 

As  above  stated,  two  compounds  having  the  formula  C4H10  are 
possible.  If  only  one  H  atom  is  substituted  in  these  compounds, 
four  different  combinations  are  possible;  thus,  on  the  introduction 
of  the  OH  group  we  obtain  four  compoimds  C4H9OH,  called  butyl 
alcohols: 

CH,  CH3  CH,         CH3  CH3         CH3 

dH,  CH-OH      \/  \/ 

I  J  CH  C-OH 

CH3  6k,  I  I 

I  I  dH20H  CH, 

CH2OH      CH3 
Isomers  which  are  due  to  the  various  positions  of  the  introduced  atoms, 
etc.,  while  the  order  of  the  members  of  the  C  chain  remains  the  same,  are 
also  called  position  isomers. 

With  the  unsaturated  compounds  the  number  of  possible  isomers  is  still 
greater  than  with  the  saturated  because  substitution  takes  place  at  differ- 
ent points  and  also  because  the  bonds  of  the  C  atoms  are  multiple  at 
certain  points. 

In  regard  to  the  special  form  of  isomerism  which  occurs  with 
compounds  with  ring-formed  C  atoms,  we  refer  to  isocarbocyclic 
and  heterocyclic  compounds. 

3.  Stereoisomerism. 

A  number  of  compounds  having  similar  qualitative  and  percentage 
composition  are  known  which  do  not  differ,  or  which  differ  in  only  a 


STEREOISOMERISM.  303 

slight  degree,  in  their  chemical  properties,  but  which  exhibit  certain 
differences  in  their  physical  properties  (for  example,  variation  in 
behavior  towards  polarized  light)  and  which  are  therefore  called 
physically  isomeric  (also  optically  isomeric)  compounds. 

One  kind  of  physical  isomerism  is  due  to  a  varied  arrangement  or 
grouping  of  the  molecules  themselves,  since  it  appears  only  in  sohd 
compounds;  thus,  for  example,  the  crystallization  of  one  and  the 
same  substance  in  two  or  more  crystal  forms  (dimorphism  and  poly- 
morphism, p.  35),  and  further  the  property  possessed  by  certain  sub- 
stances of  diverting  the  ray  of  polarized  light  only  when  in  the  solid 
state,  which  property  is  not  retained  when  the  substances  are  in  the 
liquid  or  dissolved  state,  namely,  when  the  molecules  are  free  to 
move  about  one  another  (p.  38). 

The  second  kind  of  physical  isomerism  can  be  caused  only  by  the 
arrangement  of  the  atoms  in  the  molecules,  and  is  exhibited  in  the 
case  of  certain  isomeric  compounds  which  have  the  power  of  divert- 
ing the  polarized  ray  of  light  equally  strongly  to  the  right  or  to  the 
left  when  they  are  in  the  melted  or  dissolved  condition,  namely, 
when  the  molecules  are  free  to  move  about  one  another  (optical 
isomerism).  This  kind  of  physical  isomerism  is  also  exhibited  in 
the  case  of  certain  unsaturated  isomeric  compounds  which  differ 
from  each  other  in  all  their  physical  and  in  certain  of  their  chemical 
properties. 

This  second  sort  of  physical  isomerism  cannot  be  explained 
by  the  theories  of  structure  or  constitution  (p.  30),  since  it  is  not 
apparent  from  these  how  a  difference  in  the  structure  of  the  given 
isomeric  compounds  can  be  possible,  but  it  can  be  explained  if  the 
spatial  arrangement  of  the  atoms  in  the  molecule  is  taken  into  con- 
sideration. 

Those  compounds  whose  isomerism  can  only  be  explained  on 
the  assumption  of  a  different  spatial  arrangement  of  the  atoms  in 
the  molecule  are  called  stereoisomeric  (arepeov,  solid  body)  and,  this 
isomerism  is  called  stereo-  or  space-isomerism,  also  alio-  or  geow,etric 
isomerism.  The  formulas  representing  these  compounds  are  called 
stereochemical  formulas,  and  instead  of  speaking  of  the  structure  or 
constitution  of  such  bodies  the  expression  "configuration  of  the 
molecules"  is  employed. 

The  structural  or  constitutional  formulas  represent  the  bonding 


304 


ORGANIC  CHEMISTRY. 


together  of  the  carbon  atoms  and  the  distribution  of  the  atoms  and 
radicals  combined  with  them  in  such  a  manner  that  the  formula 
always  hes  in  a  single  plane;  but  since  all  bodies,  including  mole- 
cules must  extend  in  three  dimensions,  this  is  not  expressed  in  the 
original  formulas;  indeed  these  are  actually  contradictory  to  many 
facts. 

For  example,  by  assuming  that  the  four  valences  of  carbon  all  lie  in 
one  plane,  of  all  compounds  of  the  formula  Cajbz  (where  a  and  b  represent 
different  monovalent  groups*),  there  would  be  two  isomers  possible, 
namely,  one  where  a  and  a  and  b  and  b  were  adjoining,  and  one  where 
they  were  separated  from  each  other: 


X     X 


while  in  fact  only  one  such  compound  (for  example,  only  one  methylene 
chloride,  CHgClJ  is  known  and  nothing  points  to  the  existence  of  two 
such  isomers.  Of  all  compounds  having  the  formula  Cabcd  there  must 
exist  for  each  three  isomers,  namely, 

X    X    X 

while  actually  only  two  isomers  are  known,  for  example,  two  chlorbrom- 
iodomethanes,  CHClBrl. 

When  a  spatial  configuration  is  assumed  for  the  carbon  compounds,  in 
accordance  with  the  theory  proposed  by  Le  Bel 
and  van't  Hoff  all  of  the  previously  mentioned 
difficulties  and  contradictions  disappear. 

This  theory  is  based  on  the  assumption  that 
the  four  valences  of  every  carbon  atom  are  equally 
distributed  symmetrically  about  the  space  surround- 
ing the  carbon  atom,  and  that  the  direction  of 
every  valence  forms  the  same  angle  with  the  di- 
kCt  rection  of  every  other  valence,  which  agrees  with 
the  equal  value  of  each  of  the  four  valences. 
This  is  best  represented  by  placing  the  carbon 
atom  at  the  center  of  a  tetrahedron,  the  four 
valences  being  directed  towards  the  four  solid  angles  of  the  tetrahedron. 

If  we  imagine  that  in  the  molecule  of  the  compound  Caaaa  three  of 
the  similar  groups  a  are  replaced  by  dissimilar  groups,  then  the  following 
isomers  are  possible: 

a.  Isomers  in  the  case  of  simple  saturated  compounds. 

a.  If  a  group  b   or  still  another  group  c  takes   the  place  of  one  or 

two  of   the  groups  a,  then    only  one  configuration    can    be    conceived, 

since  both  figures  can  be  made  to  correspond  by  turning,  so  that  it  is 

immaterial  on  which  angle  of  the  tetrahedron  the  substitution  takes  place 

*  The  expression  "group"  as  used  in  this  chapter  denotes  "an  atom  or  an    atomic 
group." 


Fig.  1. 


STEREOISOMERISM. 


305 


(Figs.  2  and  3).     Therefore  mono-  and  disubstitution  products  of  methane 
can  exist  only  in  one  modification,  a  fact  justified  by  experience. 

/?.  If  a  group  d,  different  from  a,  b,  c,  is  introduced  in  place  of  one  of 
the  remaining  a  groups,  then  two  different  configurations  are  obtained. 


according  to  whether  the  group  a  standing  to  the  right  or  that  to  the  left 
in  the  figure  is  replaced  by  d.  These  two  configurations  cannot  be  made 
to  correspond  to  one  another  by  turning. 

If  one  pictures,  one's  self  as  standing  at  the  point  of  attachment  of  the 
group  a,  then  in  order  to  pass  from  b  over  c  to  d  along  the  circumference 
of  the  circle  joining  these  three  points  it  would  be  necessary  to  move  in 
the  direction  of  the  hands  of  a  clock  in  one  case  (Fig.  4),  and  in  the  oppo- 
site direction  in  the  other  (Fig.  5) . 


The  two  systems  are  not  identical,  but  stand  to  each  other  in  the  same 
relation  as  an  object  stands  to  its  image  as  reflected  in  a  mirror,  and  many 
compounds  which  correspond  to  these  systems  crystallize  in  two  different 
forms  which  bear  a  similar  relation  to  one  another.  These  are  called 
enantiomorphic  crystals  (evayriaio<;,  opposite,  enantiomorphism).  Com- 
pounds of  this  kind  which  contain  an  asymmetric  carbon  atom  can  be 
optically  active,  and  this  property,  when  the  arrangement  is  that  shown 
in  Fig.  4,  is  of  an  opposite  quality  from  that  when  the  arrangement 
is  as  shown  in  Fig.  5. 

As  a  matter  of  fact  the  isomeric  compounds  with  one  asymmetric  car- 
bon atom  are  identical  in  their  chemical  and  mostly  also  in  their  physical 
properties  with  the  exception  of  their  optical  behavior,  since  there  are 
known  two  modifications  of  every  compound  with  an  asymmetric  carbon 
atom  (p.  39),  one  of  which  rotates  the  plane  of  polarization  to  the  right  and 
the  other  to  the  left  (optical  isomerism).  When  such  compounds  crystal- 
lize they  also  exhibit  enantiomorphism. 


306 


ORGANIC  CHEMISTRY, 


h.  Isomerism  in  complicated  saturated  compounds. 

Here  the  tetrahedrons  corresponding  to  the  asymmetric  carbon  atoms 
have  a  common  point  of  contact.  These  compounds  may  differ  not  only 
in  optical  properties,  but  also  in  other  physical  properties;  indeed  they 
may  show  a  slight  chemical  difference.  In  order  to  determine  the  number 
of  isomers  in  every  conceivable  case,  it  must  be  assumed  that  both 
tetrahedrons  continually  rotate  about  their  common  axis  in  the  same  or 
in  opposite  directions,  an  assumption  which  corresponds  to  the  view  that 
a  movement  of  the  atoms  in  the  molecule  is  present. 

In  the  case  of  the  rigid  combination  of  two  carbon  tetrahedrons  even 
for  compounds  which  do  not  contain  an  asymmetric  carbon  atom  (p.  39), 
as,  for  example,  for  Cga^bj,  there  would  be  three  isomers  possible;  i.e., 


or 


^t^  \!/  \F 


C  C  c 

/1\    /K    /l\ 

a  a  cC     h  a  a     a  a  b 

f Symbolic  notation.) 
Fig.  6.     Fia.  7.      Fio.  8. 


If  the  two  tetrahedrons  can  rotate  about  their  common  axis,  then  the 
arrangement  shown  in  Figs.  7  and  8  would  not  represent  isomerism,  but 
only  different  phases  of  rotation,  and  by  turning  could  all  be  brought 
into  the  same  position.  There  are  therefore  only  two  compounds  C2aib2 
possible;  and  smce,  further,  all  chemical  facts  go  to  show  that  an  influ- 
ence is  exerted  by  the  atoms  within  the  molecule,  therefore  the  one 
isomeric  compound  02^462  would  more  probably  correspond  to  Fig.  8  than 
to  Fig.  7,  since  there  different  groups  are  opposed.  Under  such  condi- 
tions, then,  on  account  of  the  opposite  attraction  of  a  and  b,  the  rotation 
can  be  completely  prevented.  With  reference  to  these  relations  the  fol- 
lowing isomers  are  possible: 

a.  If  two  asymmetric  carbon  atoms  are  present  in  the  molecule  of  a 
compound,  and  if  one  of  these  carbon  atoms  is  combined  with  groups  which 
are  similar  to  those  combined  with  the  other  carbon  atom  (for  exam  pie,  when 
thev  form  a  so-called  svmmetrical  molecule,  as  in  the  case  of  tartaric  acid, 
HOOC.OH.HC-CH-OH.COOH),  then,  in  addition  to  the  two  optically 
opposed  forms  (i.e.,  dextrotartaric  and  laevotartaric  acid),  and  the  inactive 
form  which  is  produced  by  their  combination  (e.g.,  racemic  acid),  there 
exists  a  second  inactive  form  (inactive  tartaric  acid)  which  cannot  be  split 
up  into  the  two  active  modifications.  In  order  to  explain  the  occurrence 
of  the  latter  form,  it  is  assumed  that  in  the  molecule  of  this  substance 
the  position  of  the  atoms  attached  to  one  of  the  asymmetric  carbon  atoms 
is  such  as  to  cause  rotation  to  the  right,  while  the  position  of  the  atoms 
attached  to  the  other  asymmetric  carbon  atoms,  namely,  the  other  half  of 
the  niolecule,  is  such  as  to  cause  rotation  to  the  left,  and  as  a  result  the 
rotation  of  the  molecule  as  a  whole  is  prevented  and  the  compound  is 


STEREOISOMERISM. 


307 


inactive  optically.    This  modification  cannot  be  split  up  into  two  opti- 
cally active  modifications,  because  on  decomposition  the  molecule  itself 


6/7^       ^^xF^^         ' 


J)  b 

FiQ.  9.  Fig.  10, 


h  d 


or 


/l\    /i\    /w 

d  b  G      o  b  d      c  b  d 

(Symbolic  notation.) 
Fig.  9.      Fig.  10.      Fig.  11. 


is  destroyed.  Thus,  for  example,  in  Fig.  11,  if  the  arrangement  of  the 
groups  b,  c,  d,  in  the  upper  tetrahedron  corresponds  to  a  rotation  to  the 
feft,  then  in  the  lower  half  of  the  molecule  the  arrangement  corresponds 
to  a  rotation  to  the  right,  while  in  Fig.  9  the  arrangement  b,  c,  d  in  both 
tetrahedrons  corresponds  to  a  rotation  to  the  left,  and  in  Fig.  10  it  cor- 
responds to  a  rotation  to  the  right,  representing  the  two  optically 
opposed  modifications. 

/?.  If  there  are  present  in  the  molecule  of  a  compound  two  asymmetric 
carbon  atoms  to  which  are  attached  altogether  six  different  groups  (form- 
ing a  so-called  asymmetric  molecule),  for  example,  cba-C-C-def,  then  there 
are  four  isomers  possible,  namely, 


^^>  +B' 


(2)  r^.       (3)  +^. 


Wrs' 


where  A  and  B  represent  the  two  tetrahedrons  and  +  represents  the 
arrangement  of  the  atoms  in  a  clockwise  direction  (i.e.,  dextrorotatory 
position) ,  and  —  represents  the  arrangement  of  the  atoms  in  a  counter- 
clockwise or  Isevorotatory  position. 

y.  If  three  asymmetric  carbon  atoms  are  present  in  a  single  asymmetric 
molecule,  for  example  hgfC-Cab-Ccde  (as  in  the  pentoses  and  their  corre- 
sponding acids),  then  there  are  eight  isomers  possible;  if  four  asymmetric 
carbon  atoms  are  present  in  an  asymmetric  molecule  (as  in  the  case  of  the 
hexoses),  there  are  sixteen  isomers  possible;  so  that  in  general  for  every 
compound  having  n  asymmetric  carbon  atoms  there  will  exist  2"  isomeric 
modifications  (e.g.,  for  four  asymmetric  carbon  atoms  2*=  16  isomers). 

All  of  these  isomers  are  optically  active,  because  in  the  presence  of 
different  atoms  or  atomic  groups  attached  to  the  two  asymmetric  carbon 
atoms  no  compensation  of  the  rotator)'  power  can  take  place. 

In  addition  to  these  active  modifications  it  is  still  possible  to  have 
inactive  forms  which  are  produced  by  the  combination  of  two  active  mod- 
ifications for  example,  of  1  and  4,  2  and  3,  but  not  of  1  and  2,  or  2  and 
4  (see  ,8  above). 

d.  In  the  case  of  compounds  having  three  or  more  asymmetric  carbon 
atoms  in  a  symmetric  molecule,  the  number  of  possible  isomers  (as  was 
shown  for  two  asymmetric  carbon  atoms  on  p.  306,  cc)  is  small,  and  these 


308 


ORGANIC  CHEMISTRY. 


are  in  part  optically  active,  but  in  part  optically  inactive,  and  cannot  be 
split  up  into  active  modifications  (because  of  intramolecular  compensa- 
tion, as  in  a,  Fig.  11).  In  addition  to  these  other  inactive,  resolvable 
mixtures  (racemic  modifications,  p.  39)  are  possible. 

c.  Isomerism  in  unsaturated  compounds. 

a.  Compounds  containing  carbon  atoms  connected  by  double  bonds. 

In  such  cases  the  tetrahedrons  corresponding  to  the  asymmetric  car- 
bon atoms  are  connected  together  at  two  apices,  namely,  at  one  edge, 
and  therefore  no  rotation  of  the  two  tetrahedrons  can  take  place  about 
a  common  axis.  The  atoms  or  atomic  groups  attached  to  each  of  the 
asymmetric  carbon  atoms  must  therefore  remain  fixed  in  their  original 
positions  (see  Figs.  12  and  13). 


OOOH 


H      COOH 

Y 

H     COOH 


COOH 


HOOC 


COOH 


H      COOH 


y 

or  I 

HOOC      H 


Fig.  12.— Maleic  acid,  G4H4O4.  Fia.  13.— Fumaric  acid,  C4H4O4. 

The  conditions  here  are  different  on  the  right  and  left,  although  they 
resemble  the  conditions  which  exist  when  the  asymmetric  carbon  atoms 
are  attached  by  a  single  valence,  and  when  two,  three,  or  four  different 
groups  are  attached  to  the  tetrahedrons  it  is  possible  to  recognize  two 
isomers  of  each  which  show  a  complete  difference  in  almost  all  physical 
and  also  in  certain  chemical  properties. 

Since  the  atoms  or  atomic  groups  which  are  attached  to  the  asymmetric 
carbon  atoms  all  lie  in  one  plane,  these  compounds  cannot  be  optically 
active. 

According  to  the  theory  of  structure  both  maleic  and  fumaric  acid 
must  have  the  same  formula:  HOOC-CH=CH-COOH.  In  a  spatial  repre- 
sentation of  these  two  substances  a  different  structure  is  evident  if  for  one 
acid  we  employ  the  so-called  plane-symmetric  or  as  form  (Fig.  12)  for  one 
acid  and  the  so-called  axial-symmetric  or  trans  form  (Fig.  13)  for  the  other. 
p.  Compounds  containing  carbon  atoms  connected  by  triple  bonds. 
In  this  case  the  tetrahedrons  corresponding  to  these  carbon  atoms  are 
connected  by  three  apices,  namely,  by  one  of  their  faces,  and  therefore 
jj.  form  a  double  triangular  pyramid,  so  that 
the  two  free  valences,  just  as  in  the  above 
case  a,  lie  in  one  plane.  Isomers  are  here 
impossible. 

If  one  of  the  bonds  is  severed,  then  the 
two  tetrahedrons  swing  apart.  The  two 
attached  atoms  or  atomic  groups  will  then 
lie  one  above  the  other  and  the  molecule 
becomes  plane-symmetric. 

d.  Isomerism  in  nitrogen  compounds. 
Isomers  appear  in  the  case  of  certain  oximes,  diazo-  and  azo-com- 
pounds,  in  which  a  trivalent  nitrogen  atom  is  attached  by  two  of  its 


+Bir- 


QUALITATIVE  ELEMENTARY  ANALYSIS 


309 


valences  to  a  carbon  or  nitrogen  atom,  which  can  be  explained  by  the 
assumption  that  the  three  nitrogen  valences  do  not  lie  in  a  single  plane  but 
are  distributed  in  space  like  the  four  free  valences  of  the  carbon  atom  in 
Figs.  6  to  11.  The  three  valences  of  nitrogen  are  imagined  as  directed 
towards  three  corners  of  a  tetrahedron,  the  nitrogen  atom  itseK  being 
situated  at  the  fourth  corner.  In  this  way  is  represented,  for  example, 
the  structure  of  the  two  isomeric  benzaldoximes,  HO — N  =  CH — CgHg,  as 
shown  below.     Isomers  of  this  sort  are  known  as  syn  and  onti  forms. 


HbCo 

Syn-benzaldoxime. 


HaC 


or 


N-OH 


Anti-benzaldoxime. 


DETERMINATION    OF  THE   COMPOSITION,  MOLECULAR  AND 
CONSTITUTIONAL  FORMULA. 

In  order  to  ascribe  an  empirical  and  rational  molecular  formula 
(p.  26)  to  an  organic  compound  the  following  essentials  are  necessary: 

1.  The  elements,  of  which  the  compounds  are  composed,  must 
be  determined  (qualitative  analysis). 

2.  The  proportion  in  which  the  respective  elements  exist  in  the 
compound  must  be  estimated  (quantitative  analysis). 

3.  The  molecular  weight  must  be  determined  with  reference  to 
the  qualitative  and  quantitative  composition. 

4.  The  intermolecular  arrangement  of  the  atoms  or  atomic  groups 
in  the  molecule  (the  constitutional  formula)  must  be  studied. 

I.  Qualitative  Elementary  Analysis. 

The  elements  in  an  organic  compound  can  generally  only  be 
detected  after  the  destruction  of  the  molecule  of  the  compound, 
which  may  be  done  as  follows : 

The  carbon  in  most  organic  bodies  can  be  detected  by  their  yield- 
ing black  carbon  on  heating  them  in  the  absence  of  air.  The  carbon 
can  be  more  positively  detected  by  heating  the  substance  with  copper 
oxide  (p.  236)  or  if  the  substance  is  volatile,  by  passing  the  vapors 
slowly  over  heated  copper  oxide  contained  in  a  glass  tube.  The  carbon 
in  this  case  suffers  oxidation  at  the  expense  of  the  oxygen  of  the 


310  ORGANIC  CHEMISTRY. 

copper  oxide  and  is  converted  into  carbon  dioxide,  which  can  be 
detected  by  passing  the  gas  into  Hme-water,  which  becomes  cloudy 
(p.  191). 

The  hydrogen  is  detected  by  heating  the  perfectly  dry  substance 
with  copper  oxide  in  a  glass  tube  whereby  it  is  burnt  into  water, 
which  collects  on  the  cold  part  of  the  tube. 

The  nitrogen  is  detected  by  heating  the  substance  with  potassium 
in  a  glass  tube  until  the  excess  of  potassium  is  driven  off.  The  nitrogen 
present  is  converted  into  potassium  cyanide,  which  can  be  detected 
by  the  methods  given  in  connection  with  the  cyanogen  compounds. 
Many  nitrogenous  compoimds  also  yield  ammonia  on  heating  them 
with  soda-lime. 

The  oxygen  of  these  hydroxides  unites  with  the  carbon,  forming  carbon 
dioxide,  which  combines  with  the  alkali,  forming  carbonates,  while  the 
hydrogen  at  the  moment  it  is  set  free  unites  with  the  nitrogen,  forming  am- 
monia. The  excess  of  hydrogen  escapes  as  such  or  unites  with  the  carbon, 
forming  volatile  hydrocarbons;  thus 

NCOH  +  Ca(0H)2=  CaCOs  +  NH3, 

(CN)2  +  4Ca(OH)2=  2CaC03 + 2NH3 + 2CaO  +  2H. 

Many  nitrogen  compounds  such  as  diazo  bodies  do  not  give  these 
reactions  because  they  decompose  very  readily  with  the  formation 
of  gaseous  nitrogen.  In  these  cases  we  are  obliged  to  proceed  accord- 
ing to  the  Dumas  method  (p.  312)  for  the  quantitative  estimation  of 
nitrogen. 

Oxygen  is  determined  in  the  quantitative  analysis  of  the  sub- 
stance and  indeed  generally  indirectly. 

Phosphorus  and  sulphur  are  detected  by  fusing  the  substance 
with  a  mixture  of  sodium  carbonate  and  potassium  nitrate,  which 
converts  them  into  phosphoric  and  sulphuric  acids.  These  are  de- 
tected in  the  watery  solution  of  the  fused  mass  after  acidification 
with  nitric  acid  as  ammonium  phosphomolybdate  (p.  169)  and  barium 
sulphate  (p.  130)  respectively.  With  volatile  substances  the  oxida- 
tion into  sulphuric  and  phosphoric  acids  is  brought  about  by  heating 
the  substance  with  fuming  nitric  acid  in  sealed  glass  tubes. 

The  halogens  are  converted  into  calcium  halogen  salts  by  heating 
the  substance  with  calcium  oxide  (with  volatile  substances  in  sealed 
glass  tubes)  and  then  detected  in  the  watery  solution,  after  acidifi- 
cation with  nitric  acid  by  silver  nitrate  (pp.  136,  141,  143). 


QUANTITATIVE  ELEMENTARY  ANALYSIS,  311 

On  heating  an  organic  halogen  compound  on  a  platinum  wire  with 
copper  oxide  in  a  non-luminous  flame  a  blue  or  green  color  is  given 
to  the  flame.  On  heating  organic  halogen  compounds  with  fuming 
nitric  acid  and  silver  nitrate  in  sealed  glass  tubes  an  insoluble  silver 
halogen  precipitate  is  obtained. 

The  remaining  elements  are  to  be  sought  for,  if  they  are  not 
volatile,  in  the  residue  obtained  on  the  incineration  of  the  substance, 
the  ash,  and  if  volatile  in  the  colorless  Hquid  finally  obtained  on  boil- 
ing the  substance  with  concentrated  sulphuric  acid. 

2.  Quantitative  Elementary  Analysis. 

a.  Determination  of  the  Elements. 
Determination  of  the  Carbon  and  Hydrogen, 

A  weighed  amount  of  the  substance  is  mixed  with  copper  oxide 
and  introduced  into  a  tube  of  infusible  glass  to  the  open  end  of  which 
is  attached  a  weighed  calcium  chloride  tube  and  to  this  a  weighed 
potash  bulb.  The  contents  of  the  tube  is  heated  to  a  red  heat  whereby 
the  carbon  is  burnt  into  carbon  dioxide  and  the  hydrogen  into  water; 
this  water  is  vaporized  and  is  retained  in  the  calcium  chloride  tube 
while  the  carbon  dioxide  is  absorbed  by  the  caustic  potash  in  the  bulb. 
After  complete  combustion  both  tubes  are  re  weighed  in  order  to 
determine  the  weight  of  carbon  dioxide  and  water  formed,  from 
which  the  amount  of  C  and  H  in  the  weighed  amount  of  substance 
can  be  calculated  (p.  312). 

Determination  of  Nitrogen.  Estimation  as  Ammonia,  a.  Will- 
Varrentrap  method,  A  weighed  amount  of  the  substance  is  mixed 
with  soda-lime  and  introduced  into  a  hard-glass  tube  the  open  end  of 
which  is  connected  with  an  apparatus  filled  with  hydrochloric  acid. 
The  contents  of  the  tube  is  heated  and  the  gases  produced  allowed 
to  bubble  through  the  hydrochloric  acid,  which  combines  with  all 
the  ammonia  produced  (see  p.  310).  The  ammonium  chloride  formed 
is  precipitated  as  insoluble  ammonium  platino-chloride,  (NH4)2PtCl8 
(p.  293),  which  is  collected,  dried,  weighed,  and  the  nitrogen  calculated 
therefrom. 

/?.  Kjeldahl  Method.  A  weighed  amount  of  the  substance  is  heated 
with  concentrated  sulphuric  aoid  and  certain  metallic  oxides  (CuO, 
HgO)  which  have  an  oxidizing  action,  until  a  complete  solution  has 
taken  place  and  the  fluid  is  clear.     The  ammonia  which  is  produced 


312  ORGANIC  CHEMISTRY, 

from  the  nitrogen  in  this  method  and  which  exists  in  the  liquid  aa 
ammonium  sulphate  is  driven  off  by  distillation  with  caustic  alkali 
and  determined  as  described  in  method  a. 

Estimation  as  Gaseous  Nitrogen.  Dumas  Method.  Many  arti- 
ficially prepared  organic  compounds  contain  nitrogen  in  the  form  of 
NO,  NO2,  NO3,  etc.;  this  nitrogen  is  not  completely  converted  into 
ammonia  on  heating  with  soda-lime  or  on  boiling  with  H2SO4;  hence 
their  nitrogen  must  be  determined  by  the  following  method,  which 
is  applicable  for  all  nitrogenous  compounds.  A  weighed  amount  of 
the  substance  is  mixed  with  copper  oxide  and  heated  in  a  glass  tube 
free  from  air  and  which  contains  copper  turnings  at  one  end.  The 
gases  produced,  which  consist  of  water,  carbon  dioxide,  nitrogen, 
are  collected  in  a  graduated  glass  tube  filled  with  caustic  alkali.  As 
the  gases  pass  through  the  red-hot  copper  turnings  any  oxides  of 
nitrogen  which  may  have  been  produced  are  decomposed,  the  oxygen 
uniting  with  the  Cu  and  the  nitrogen  being  set  free.  The  carbon 
dioxide  and  water  are  not  decomposed,  but  are  absorbed  by  the  caustic 
alkah,  so  that  the  gas  collected  in  the  graduated  tube  consists  of 
pure  nitrogen  and  its  volume  is  readily  determined. 

From  the  cubic  centimeters  of  nitrogen  obtained  (F)  the  weight  of 
nitrogen  (N)  can  be  calculated  according  to  the  formula  (p.  42),  where  T 
represents  the  temperature,  B  the  barometric  pressure,  and  W  the  tension 
of  the  caustic  alkali  solution. 

(1  c.c.  N  weighs  0.00125  gram  at  0°  C.  and  760  mm.  pressure.) 

The  estimation  of  phosphorus,  sulphur,  and  the  halogens  is  performed 
as  described  in  the  quahtative  analysis,  but  here  the  precipitates 
obtained  are  weighed  and  the  amount  calculated  therefrom. 

Estimation  of  Oxygen.  This  is  generally  done  indirectly  in  that 
all  the  other  constituents  are  quantitatively  determined  and  their 
weight  subtracted  from  the  weight  of  the  substance  analyzed.  The 
difference  represents  the  weight  of  the  oxygen  in  the  substance. 

b.  Calculation  of  the  Analysis. 
In  order  the  better  to  compare  the  results  of  the  different  analyses, 
the  results  obtained  are  calculated  on  100  parts  by  weight  of  the 
substance,  and    the   difference  between  the  sum   of    the   elements 


DETERMINATION  OF  THE  MOLECULAR  FORMULA.  313 

estimated  and  100  represents  the  oxygen  which  was  not  directly 
estimated.  If  these  percentages  are  divided  by  the  atomic  weights 
of  the  respective  elements,  we  obtain  figures  which  represent  the 
relationship  existing  between  the  elements  of  the  compound. 

Thus  on  the  qualitative  examination  of  pure  acetic  acid  it  was  found 
apparently  to  contain  carbon  and  hydrogen;  0.395  gram  acetic  acid 
yielded  on  combustion  0.5793  gram  COg  and  0.2349  gram  HgO.  From 
these  results  we  calculate  the  amounts  of  carbon  and  hydrogen  as  follows: 

CO2  :C      =  confound  :C. 

44:12    =0.5793         :x.     a:=0.158C. 

H2O  :H2   =H20  found  :H2. 

18.02:2.02=0.2349         :x.     a:=0.0261H. 

Calculated  in  percentage  we  find  the  following: 

0.395  gram  acetic  acid: 0.1580  gram  C=  100: a;.     a:=40. 
0.395     "         "        ''    :0.0261     "    H=100:a;.     a:=6.6. 

From  this  we  see  there  is  a  difference  of  53.4  grams  (100  — [40  +  6.6]= 
53.4),  which  must  be  the  weight  of  oxygen  in  the  substance,  as  no  other 
element  was  found  on  qualitative  testing. 

One  hundred  parts  acetic  acid  therefore  consist  of: 

Carbon 40.0  parts 

Hydrogen 6.6      " 

Oxygen 53.4      '* 

If  these  figures  are  divided  by  the  atomic  weights  of  the  respective  ele- 
ments, we  obtain  the  relative  number  of  atoms  which  the  compound  con- 
tains: 

12=3.3  C.         ^=6.6  H.         ^*=3.3  0. 
12  1  16 

The  atoms  in  acetic  acid  have  the  following  relationship  to  each  other: 
3.3:6.6:3.3  (as  the  atoms  are  indivisible,  hence  no  fractions  are  possible, 
we  call  the  lowest  number=l);  then  the  relationship  is  1:2:1,  and  hence 
CH2O  =  30  represents  the  simplest  expression  for  the  molecule. 

3.  Determination  of  tlie  Molecular  Formula. 

The  formula  calculated  from  the  elementary  analysis  of  a  com- 
pound may  indeed  represent  its  true  molecular  weight,  but  it  may  also 
be  a  multiple  of  the  formula,  hence  the  determination  of  the  molecu- 
lar weight  must  follow  the  analysis. 

The  above  formula,  CH2O  =  30,  represents  the  simplest  formula  for 
acetic  acid,  but  we  know  of  many  compounds  having  entirely  different 


314  ORGANIC  CHEMISTRY. 

chemical  and  physical  properites  which  on  elementary  analysis  also  give 
the  same  formula  CHgO;  hence  it  is  probable  that  their  molecular  weights 
are  different. 

Before  the  molecular  formula  is  decided  upon  it  should  be  noted 
whether  the  simplest  formula  found  by  analysis  coincides  with  the 
law  of  even  numbers,  which  is  that  the  sum  of  the  elements  with 
uneven  valences  (i.e.,  univalent  and  trivalent,  such  as  H,  CI,  Br,  I 
and  N,  P,  As)  of  each  C  compound  must  be  an  even  number. 

This  law  can  be  explained  by  the  fact  that  the  carbon  is  tetravalent 
and  that  the  elements  combine  according  to  their  atomicity.  Thus  in 
cyanuric  acid,  C3H3N3O3,  the  sum  of  the  N  and  H  atoms  =  6 ;  in  ammonium 
trichloracetate,  C2Cl3(NH4)02,  the  sum  of  the  CI,  N,  and  H  atoms  =8. 
If  in  the  analysis  of  cyanuric  acid  the  formula  C3H2N3O3  was  derived 
there  must  be  some  mistake  in  the  analysis,  as  the  sum  of  the  elements 
with  uneven  valences  is  5,  an  uneven  number. 

a.  Methods  depending  upon  the  determination  of  the  specific  gravity 
of  the  gaseous  compound  {gas  or  vapor  density  of  the  compound,  p.  18). 

If  the  compound  is  a  gas  or  can  be  vaporized  without  decompo- 
sition all  that  is  necessary  is  to  determine  the  gaseous  volume  ob- 
tained from  a  known  weight  of  the  substance  and  to  calculate  from 
this  the  weight  of  the  volume  of  the  gaseous  compound  as  com- 
pared to  an  equal  volume  of  oxygen  taken  as  32. 

For  example,  0.134  gram  acetic  acid  yield  50  cc.  gas  (reduced  to  0* 
and  760  mm.  pressure,  p.  42),  and  as  50  cc.  oxygen  (at  0°  and  760  mm.) 
weigh  50X0.01429  grams=  0.0715  grams  (p.  107),  then  the  molecular 
weight  of  acetic  acid  is  60;  e.g.. 

Weight  of  50  cc.  oxygen         "Weight  of  50  cc.  acetic  acid 

0.0715  :  0.134 

Molecular  weight  of  O  Molecular  weight  of  acetic  acid 

=32  :  X  {x=m). 

The  vapor  density  of  a  gaseous  compound  may  be  determined  by  first 
weighing  a  glass  vessel  free  from  air  and  then  filled  with  the  gas  in  question. 

The  following  rapid  and  easy  methods  may  be  used  for  liquid  and  solid 
compounds. 

Vapor  Density  Determination  according  to  A .  W.  Hofmann.  The  method 
ordinarily  used  (see  page  315),  is  only  applicable  for  those  substances 
which  are  not  decomposed  at  temperatures  above  their  boiling-point. 
In  other  cases  a  weighed  amount  of  substances  is  introduced  into  the 
vacuum  in  a  barometer  tube  and  vaporized  and  the  volume  of  the  vapor 
determined.  In  this  manner  the  vapor  density  can  be  determined  at 
temperatures  50  to  100°  below  the  boiling-point  of  the  substance  at  ordi- 
nary pressures,  so  that  the  substance  is  not  decomposed. 


DETERMINATION  OF  THE  MOLECULAR  FORMULA,  315 


Determination  of  the  Vapor  Density  by  the  Expulsion  of  Air  according 
to  Victor  Meyer.  The  vessel  b,  which  is  constructed  of  glass  or  porcelain 
and  which  contains  air,  is  heated  in  the  large  tube  c  by  ^ 

the  vapors  of  the  liquid  contained  therein  (water, 
boihng-point  100°;  aniline,  boiling-point  183°-  diphe- 
nylamine,  boiling-point  310°),  or  by  molten  lead  (at 
about  1000°)  until  the  temperature  is  constant  or 
until  no  more  air-bubbles  rise  from  the  tube  a  at  f  The 
graduated  tube,  which  is  full  of  water,  is  now  adjusted 
over  the  opening  of  tube  a  and  the  glass  tube  b  opened 
at  d  and  a  weighed  amount  of  the  substance  quickly 
introduced  and  the  cork  at  d  quickly  replaced.  The 
substance  rapidly  vaporizes  and  expels  from  b  a  quan- 
tity of  air  corresponding  to  its  vapor  volume,  which 
collects  in  the  graduated  tube  g.  The  volume  of  air  read 
off  in  the  tube  corresponds  to  an  equal  volume  of  the 
vapor  of  the  substance  in  question  just  as  if  it  were 
possible  to  obtain  the  vapor  of  the  substance  at  ordinary 
temperatures. 

B.  Methods  depending  upon  the  determination  of 
the  elevation  of  the  boiling-point  and  depression  of 
the  freezing-point  (p.  19). 

The  depression  of  the  freezing-point  or  the 
elevation  of  the  boiUng-point  for  the  molecular 
weight  of  a  body  in  dilute  solution  is  constant  for 
various  substances  when  equal  quantities  of  the 
same  solvent  are  used.  In  order  to  find  the  con- 
stant, (K),  the  freezing-point  depression  or  the 
boiling-point  elevation  (T)  produced  by  a  few 
grams  (P)  of  a  substance  of  known  molecular 
weight  when  dissolved  in  100  grams  of  the  solvent 
is  determined  and  then  calculated  upon  the  molec- 
ular weight  of  the  respective  substance  as  follows: 

P  :  T'-'M  :  K;  hence  TxM-PxK; 
TxM 


hence 


K 


A  few  grams  (P)  of  the  substance  of  imknown  molecular  weight 

are  dissolved  in  100  grams  of  the  solvent  whose  constant  (K)  has 

been  determined  and  the  depression  of  the  freezing-point  or  elevation 

of  the  boiling-point  (T)  determined  and  the  molecular  weight  (M) 

KxP 
calculated  according  to  the  equation  M  =  —=^ — . 


316  ORGANIC  CHEMISTRY. 

For  example,  2.721  grams  acetic  acid  (P)  dissolved  in  100  parts  benzol 
iK=4Q)   depressed  the  freezing-point  2.222°   {T),  hence  the  molecular 

49x2  721 
weight  of  acetic  acid  M= —      ^  — =60,  which  corresponds  to  the  figure 

obtained  by  the  vapor  density  and  shows  that  the  simplest  formula  ob- 
tained for  acetic  acid  by  chemical  analysis,  CH20= 30,  must  be  double;  that 
is,  C2HA=60. 

C  Chemical  methods. 

The  physical  methods,  on  account  of  the  ease  with  which  they 
are  performed,  have  replaced  the  chemical  methods.  The  latter 
methods  must  be  different,  depending  upon  the  chemical  properties 
of  the  substance  investigated. 

If  the  compound  is  an  acid  the  molecular  weight  may  be  deter- 
mined after  the  basicity  has  been  learned  by  the  analysis  of  its 
salts,  when  generally  the  easily  purified  silver  salt  is  used,  which 
on  incineration  leaves  metallic  silver,  which  can  be  directly  weighed 
and  the  molecular  weight  of  the  acid  calculated  from  this  result. 
With  a  monobasic  acid  the  quantity  by  weight  which  unites  with  1 
atom  of  silver  represents  its  molecular  weight  minus  1  atom  hydrogen. 

For  example,  acetic  acid,  which  by  analysis  (p.  313)  may  have  the 
formula  CHgO  or  a  multiple  thereof,  is  a  monobasic  acid,  and  hence  in  its 
molecule  1  atom  H  is  replaceable  by  1  atom  of  a  univalent  metal.  If 
now  by  analysis  we  determine  how  much  acetic  acid  is  combined  with 
1  atom  of  silver,  then  we  obtain  the  molecular  weight  of  acetic  acid 
minus  1  atom  H. 

One  hundred  parts  silver  acetate  yield  64.68  parts  silver  on  incinera- 
tion, while  35.32  parts  are  lost.  The  acetic  acid  united  with  1  atom  of 
silver  (108  parts)  in  silver  acetate  will  be  59  parts  by  weight: 

64.68  :  35.32  ::  108:  x;    a;=59. 

Silver.  At.  wt. 

Silver. 

Now,  as  in  acetic  acid,  1  atom  H  is  replaced  by  1  atom  Ag,  hence  its 
molecular  weight  is  59  + 1  =  60,  which  corresponds  to  the  formula  CaH^Og. 
The  formula  cannot  be  CH2O,  otherwise  the  molecular  weight  would  be 
30  and  cannot  be  CgHgOg,  because  then  the  silver  salt  must  contain  1^ 
atoms  silver,  which  is  impossible.  The  formulae  C4Hg04,  CgHigOe  are 
only  possible  if  the  acetic  acid  was  bi-,  tri-,  etc.,  basic. 

If  the  compound  is  a  base  the  molecular  weight  may  be  deter- 
mined by  the  analysis  of  its  salts.  For  instance,  all  organic  bases 
form  salts,  by  direct  addition  with  acids,  analogous  to  ammonia.  I 
HCl  is  used  in  the  formation  of  the  salt,  then  the  quantity  by  weight  of 
a  monoacid  ( =  monovalent)  base  which  unites  with  one  molecule  HCl 


I 


DETERMINATION  OF  THE  CONSTITUTIONAL  FORMULA.  317 

or  of  a  biacid  base  which  unites  with  2  molecules    HCl  represents 
the  molecular  weight  of  the  base. 

We  generally  make  use  of  the  hydrochlorplatinic  acid  salt  of  the  base 
instead  of  the  HCl  salt,  as  this  forms  compounds  corresponding  to  the 
ammonium  compound  (NH4)2PtCl6,  having  an  analogous  composition. 
These  can  be  prepared  readily  in  a  pure  form  generally  with  water  of 
crystallization  and  leave  platinum,  which  can  be  directly  weighed  on 
incineration  and  the  molecular  weight  calculated  from  its  weight. 

If  the  compound  is  indifferent,  then  the  molecular  weight  may  often 
be  determined  by  the  preparation  of  simple  substitution  products,  or 
the  quantitative  relationship  of  the  individual  constituents  having 
known  molecular  weight,  of  which  the  compound  is  constructed, 
may  be  investigated  after  cleavage. 

With  compounds  containing  hydrogen  we  can  generally  replace  one  H 
atom  by  a  halogen  atom  and  the  substitution  product  obtained  can  be 
analyzed.  Naphthalin,  according  to  analysis,  has  the  formula  C5H4  or  a 
multiple  thereof.  The  analysis  of  bromnaphthalin  shows  that  one  atom  H 
is  replaced  in  C^oHg  oy  one  bromine  atom,  while  the  formulae  CjoHje,  C30H24, 
etc.,  are  excluded,  as  we  know  of  no  compound  in  which  ^V*  s'l*  ^^c,  of  the 
hydrogen  is  replaced  by  halogens. 

If  the  molecular  weight  cannot  be  determined  either  by  physical  or 
chemical  methods,  the  simplest  formula  found  by  analysis  must  be  suffi- 
cient, and  at  the  same  time  the  law  of  even  numbers  must  be  considered 
(p.  313). 

4.  Determination  of  the  Constitutional  Formulae. 

If  in  a  compound  we  have  determined  the  composition  as  well 
as  molecular  weight  (empirical  molecular  formula),  still  it  is  impossible 
to  characterize  the  compound  by  the  formula  thus  obtained  and  to 
prevent  a  confusion  with  other  compounds.  We  have  seen  that  a 
great  number  of  isomeric  compounds  are  possible,  i.e.,  compounds 
having  the  same  composition  and  the  same  molecular  weight;  thus  we 
learned  on  page  302  that  four  compounds  having  the  formula  C4H10O 
are  known,  and  it  is  therefore  necessary,  as  soon  as  it  does  not  follow 
from  circumstances  which  of  these  four  is  meant,  that  the  chemical 
formulae  simultaneously  express  the  constitution  or  structure,  i.e., 
the  inner  construction,  of  the  compound  in  question. 

The  construction  of  a  compound  as  represented  by  the  consti- 
tutional formula  (rational  molecular  formula)  is  not  the  result  of 
theoretical  speculation,  but  these  formulae  must  be  derived  from 
the  study  of  the  decompositions,  cleavages,  and  methods  of  formation 


318  ORGANIC  CHEMISTRY. 

of  the  respective  compound  and  serve  the  purpose  of  giving  us  an 
exact  representation  of  the  chemical  nature  of  the  compound,  of 
caUing  our  attention  from  what  other  compounds  it  is  derived  and  into 
which  it  can  be  converted,  etc. 

The  investigation  of  the  constitutional  formula  is  of  special  impor- 
tance for  organic  compounds  (carbon  compounds) ,  as  by  these  means 
important  natural  products  for  man  have  been  artificially  prepared. 
This  is  easier  for  organic  compounds  than  for  inorganic  ones,  as  the 
carbon,  although  the  multiplicity  of  its  compounds,  shows  in  many 
ways  a  more  regular  behavior  than  the  other  elements.  We 
are  therefore  able  to  give  well-based  constitutional  formula  for 
most  organic  compounds,  while  this  is  not  possible  for  many  of  the 
much  simpler  constructed  inorganic  compounds. 

In  the  construction  of  the  constitutional  formulae  for  organic 
compounds  we  ordinarily  try  to  decompose  the  complicated  com- 
pounds into  simpler  ones  of  known  constitution  (analytical  method), 
or  we  prepare  complicated  compounds  step  by  step  from  simple 
compounds  of  known  constitution  (synthetical  method);  still  the 
various  physical  properties  of  the  compound  also  help  us  in  the 
elucidation  of  its  constitution. 

1.  Chemical  Methods. 

By  oxidation  we  differentiate  between  the  primary  alcohols  which 
first  yield  aldehydes  and  secondary  alcohols  which,  under  the  same  con- 
ditions, yield  ketones;  and  tertiary  alcohols,  which  yield  acids,  having  fewer 
C  atoms.  Aldehydes  differ  from  the  isomeric  ketones  by  yielding,  on 
oxidation,  acids  having  the  same  number  of  C  atoms,  while  the  ketones 
yield  acids  with  fewer  C  atoms.  Aromatic  compounds  which  contain  the 
aliphatic  side-chain  attached  to  the  benzol  nucleus  are  readily  oxidized,  as 
of  the  entire  side-chain  only  that  C  atom  which  is  directly  united  to  the 
benzol  nucleus  is  converted  into  the  COOH  group,  while  the  other  C  atoms 
of  the  side-chain  are  split  off  and  oxidized;  thus 

CeH,=  (CH3),  +  60  =  C,H,(C00H)2  +  2H,0 ; 

CeH,=  (CHg-CHg)^  + 120  =  C6H,(COOH)2  +  200^  +  4H2O. 

By  reduction  we  can  differentiate  between  nitro-compounds  and  their 
isomers,  the  nitrite  esters.  The  first  yield  amines  with  nascent  hydrogen, 
while  the  latter  yield  alcohols: 

C2H5NO2  +  6H = C^H.NH^  +  2H2O ; 

Nitroethane.  Ethylamine. 

C^Hs-O-NO  +  GH-CgHpH  +NH3  +  H2O. 
Ethyl  nitrite.  Ethyl  alcohol. 


DETERMINATION  OF  THE  CONSTITUTIONAL  FORMULA.  319 

Primary  sulphurous  acid  esters  are  converted  into  alcohols  by  naacent 
hydrogen,  while  the  isomeric  suiphonic  acids  give  mercaptans: 

C2H5-0-SO-OH  +  6H  =  C2Hs-OH  +  2H20  +  H2S; 

Ethyl  sulphite.  Ethyl  alcohol. 

C2H5-SO2-OH  +  6H     =C2H,SH     +     3H2O. 

Ethyl  sulphouic  acid.  Ethyl  mercaptan. 

The  splitting  off  of  carbon  dioxide  often  gives  important  information 
as  to  the  constitution  of  a  compound.  Acetic  acid  heated  with  lime  yields 
marsh-gas:  C2H402  +  CaO  =  CaC03  +  CH4.  Benzoic  acid  heated  with  lime 
yields  benzol:  CyngOg  f  CaO  =  CaC03  +  C6H6.  From  this  it  follows  that 
benzoic  acid  is  related  to  benzol  in  the  same  manner  as  acetic  acid  to 
marsh-gas.  Those  organic  bodies  which  are  obtained  by  splitting  off  of 
CO2  generally  have  the  prefix  pyro. 

The  methods  of  preparation  of  compounds  richer  in  carbon  from  those 
poorer  in  carbon  are  of  importance  in  the  study  of  the  constitution. 

From  methane,  by  the  action  of  chlorine,  we  obtain  methyl  chloride, 
CH3CI,  from  which  all  the  derivatives  of  methane  can  be  prepared.  Carbon 
and  hydrogen  unite  with  the  formation  of  acetylene,  C2H2,  which  can  be 
converted  into  ethylene,  CgH^,  and  ethane,  C^g,  by  nascent  hydrogen,  and 
from  these  a  large  number  of  other  compounds  can  be  obtained.  If  acety- 
lene is  passed  t?hrough  a  tube  heated  red-hot,  it  is  converted  into  benzol, 
CgHg,  from  which  a  great  number  of  cyclic  compounds  may  be  obtained. 

Sodium  combinations  of  organic  substances  are  decomposed  by  organic 
halogen  compounds,  so  that  the  sodium  haloid  salt  is  formed  and  the  two 
organic  residues  unite;  thus  CHg-Na  +  CH^Cl^CHg-CHg  (ethane)  +NaCl. 

If  carbon  dioxide  is  passed  into  a  sodium  compound  of  a  hydrocarbon, 
then  the  salt  of  an  acid  richer  by  one  atom  C  is  obtained:  CH3~Na  +  C02 
=  CH3C00Na  (sodium  acetate). 

The  halogen  compounds  of  the  hydrocarbons  of  the  methane  series  or 
the  suiphonic  acids  of  the  benzol  series  yield  cyanides  of  the  hydrocarbons 
on  heating  with  potassium  cyanide  (KCN).  In  these  compounds  the 
cyanogen  group  (CN)  is  converted  into  the  carboxyl  group  (COOH)  on 
heating  with  water: 

CHg-a  +KCN    =KC1  +  CH3-CN  (methyl  cyanide); 
CH3-CN-t-2HOH  =  NH3+CH3-COOH  (acetic  acid). 

Condensation  consists  in  the  union  of  two  or  more  molecules  of  the 
same  or  different  organic  substances  forming  one  molecule  by  union 
through  the  C  atoms,  generally  by  the  elimination  of  HgO,  HCl,  NHg,  COg. 
The  components  cannot  be  split  off  from  the  new  molecule  by  simple 
means. 

Condensation  takes  place  readily  amongst  the  aldehydes  and  ketones 
and  can  indeed  be  brought  about  by  the  direct  action  of  two  substances 
upon  each  other.  This  condensation  is  generally  brought  about  by  the 
presence  of  certain  bodies  such  as  aluminium  chloride,  potassium  bisul- 
phate,  anhydrous  sodium  acetate,  sodium  hydroxide,  hydrochloric  acid, 
sulphuric  acid,  zinc  chloride,  etc. 


320  ORGANIC  CHEMISTRY. 

Aluminium  chloride  brings  about  the  union  of  chlorine  derivatives  of 
the  methane  series  with  hydrocarbons  of  the  benzol  series:  CjHj  +  C^HgCl 
=  C,ll,-C^,+iiCl  CeHe  +  20^^,01  =  CeH,=(C^^ ,  +  2HC1.  CeH,  + 
3C^,a  =  CeH3-(C,H,)3  +  3HCl. 

Concentrated  sulphuric  acid  causes  the  union  of  combinations  of  the 
benzol  series  with  aldehydes: 

2CeHe+CH3-CHO=CH3-CH=(C^^2+HA 

Polymerization  depends  upon  the  union  of  several  similar  molecules 
of  a  simpler  constituted  organic  substance,  without  the  elimination  of 
atomic  groups,  forming  a  complicated  molecule.  The  original  substances 
can  be  readily  split  from  this  new  molecule.  Polymerization  takes  place 
with  unsaturated  hydrocarbons,  aldehydes,  and  cyanogen  compounds.  If  a 
compound  contains  a  C  atom  united  with  a  polyvalent  element  or  radical 
by  more  than  one  valency,  then  at  this  position  a  rupture  may  take  place 
forming  a  simple  union,  whereby  the  molecules  having  these  free  affinities 
unite  with  one  another  (see  under  example  2) .  In  this  case  a  union  of  the 
molecules  does  not  entirely  take  place  through  the  C  atoms  as  we  find  in 
condensation  (see  under  example  1). 


CH3  H  H    C] 

itylene.  H    H     H  ^H  /\ 


H    H    H 
C_H  C— C=C  CH 


Acetylene 


/\ 


Benzol.  Aldehyde.  H       CHg 

Paraldehyde. 

2.  Physical  Methods. 

Specific  Gravity.  This  is  different  for  isomeric  compounds.  The  quo- 
tient of  the  specific  gravity  divided  into  the  molecular  weight,  called  the 
molecular  volume  (p.  36)  of  liquid  organic  compounds  may  give  us  infor- 
mation as  to  the  constitution  of  the  bod)^  if  they  are  compared  at  certain 
temperatures  such  as,  for  instance,  at  their  boiling-points.  Thus  many 
homologous  series  show  an  increase  of  the  molecular  volume  of  approxi- 
mately 22  for  every  additional  CHg  (ethyl  alcohol  molecular  volume  =  62.5, 
butyl  alcohol  molecular  volume  =  84.8,  etc.)  when  they  have  the  same 
atomic  grouping,  and  in  many  cases  a  deviation  from  this  rule  shows 
another  atomic  grouping. 

Chlorine  or  bromine  atoms  substituted  for  H  atoms  in  organic  com- 
pounds occupy  a  greater  volume  when  they  are  united  to  the  same  C  atom 
as  compared  with  different  C  atoms,  etc. 

Melting-  and  Boiling-points.  Isomeric  bodies  have  different  melting- 
and  boiling-points.  In  general  an  organic  body  is  more  readily  fusible 
and  more  volatile  the  simpler  the  molecule  is  constituted,  and  the  more 
complicated  the  molecule  is,  the  higher  are  the  melting-  and  boiling- 
points,  and  the  molecules  suffer  decomposition  readily  by  heat. 

The  boiling-point  determination  is  an  important  aid  in  the  inves- 
tigation of  the  constitution  of  organic  bodies.  Homologous  compounds 
(i.e.,  those  which  differ  from  each  other  by  CHg)  with  the  same  atomic 
grouping  show  approximately  the  same  variation  in  boiling-point,  while 


ACTION  OF  CHEMICAL  AGENTS.  321 

isomeric  compounds  with  different  atomic  grouping  differ  markedly  in 
boiling-point,  thus: 

Boiling-point. 

Ethyl  alcohol,  C2H8O  78.4°  i  Difference  19 

Normal  propyl  alcohol,  CgHgO  97.4°.  ^^ 

Normal  butyl  alcohol,  QHioO  115.0°  f  ^"'^ 

Acetic  acid,  C^HA  119.0°'  u         22 

Propionic  acid,  CgHgOg  141.0°  > 

Normal  butyric  alcohol,  C.HgO^  162.0°  f         "  21 

Amongst  the  isomeric  aliphatic  compounds  the  normal  compounds 
always  have  the  highest  boiUng-point.  The  boiling-point  becomes  lower 
the  more  branches  the  carbon  chain  has. 

Of  the  disubstitution  derivatives  of  benzol  the  ortho  compounds  nearly 
always  have  a  lower  boiling-point  than  the  meta  and  para  compounds. 

The  melting-points  also  show  certain  relationships  to  the  constitu- 
tution  of  the  compounds. 

Among  the  disubstitution  products  of  benzol  the  para  compounds 
nearly  always  have  a  higher  melting-point  than  the  ortho  or  meta  com- 
pounds. With  the  normal  acids  of  the  formic  and  oxalic  acid  series  the 
introduction  of  one  CHj  group  causes  a  rise  in  the  melting-point,  while 
the  next  CHg  group  causes  a  lowering,  so  that  the  members  of  the  series 
with  uneven  C  atoms  have  a  lower  melting-point  than  both  neighboring 
members  with  even  C  atoms;  thus, 

Formic  acid,  CHgOg*  ™elts  at       -1-8.4°;    Acetic  acid,  CgH^Og,  at  -M7° 
Propionic  acid,  CsHgOg,  melts  at  —22°;      Butyric  acid,  C4H8O2,  at  —  8° 

With  isomeric  bodies  the  melting-point  is  higher  the  more  side  chains 
are  present. 

Refraction  of  Light.  The  molecular  refraction  of  liquid  organic 
compounds  is  equal  to  the  sum  of  the  atomic  refraction  (p.  38). 

The  univalent  elements  in  organic  compounds  have  a  constant  atomic 
refraction,  while  with  the  polyvalent  elements  the  refraction  is  raised 
according  to  the  double  or  treble  bonds  (also  for  the  C  atoms). 

In  the  homologous  series  the  molecular  refraction  increases  at  a- con- 
stant rate,  namely,  4.5  for  each  CHj  group. 

Rotation  of  the  Plane  of  Polarization.  This  also  gives  us  information 
as  to  the  constitution  of  an  organic  compound,  as  an  optically  active 
organic  compound  must  contain  one  or  more  asymmetric  carbon  atoms 
(p.  39). 

TRANSFORMATIONS  AND  DECOMPOSITIONS. 
I.  Action  of  Chemical  Agents. 

Oxygen  at  ordinary  temperatures  acts  upon  only  a  few  combinations, 
while  at  a  red  heat  they  all  suffer  combustion. 

Active  or  nascent  oxygen  (from  manganese  dioxide,  or  potassium 
bichromate  and  sulphuric  acid)  unites  either  directly,  or  removes  H  in 
the  form  of  water,  or  brings  about  both  changes  simultaneously. 


322  ORGANIC  CHEMISTRY. 

Halogens  have  a  substituting  action.  Unsaturated  compounds  are  first 
converted  in  saturated  ones  by  addition: 

C2H4  +  2C1=  CaH^Cl^;    C2H4CI2 + 4C1= C2H2CI, + 2HC1. 

Iodine  is  substituted  only  in  the  presence  of  an  oxidizing  substance 
(HgO,  HIO3,  etc.)  which  destroys  the  HI  produced.  This  HI  would 
otherwise  reduce  the  iodide  fojmed;  e.g.,  CH4  +  l2=CH3l  +  HI;  CH^ 
+  HI=CH,  +  l2. 

In  the  presence  of  water  the  halogens  have  an  oxidizing  action  in 
that  they  decompose  water,  setting  free  oxygen,  which  acts  upon  the  organic 
compounds:   H20  +  2Cl=2HCl  +  0. 

Ferric  chloride  has  a  weak  oxidizing  action  in  that  it  is  converted 
into  FeCl2 :CeH,(0H)2  +  2FeCl3=  CgH^O^  +  2HC1  +  2FeCl2. 

Hydrochloric,  hydrobromic,  and  hydroiodic  acids  replace  the  alcoholic 
hydroxyl  groups  (p.  333)  by  chlorine,  bromine,  and  iodine:  CgHgOH 
+  HC1=C2H5C1  +  H20.  In  the  presence  of  an  excess  of  HI  the  iodide 
formed  is  reduced  (see  above). 

Sulphuric  acid  acts  upon  the  alcoholic  hydroxyl  groups  in  the  same 
way  as  upon  the  hydroxyl  groups  of  the  metals: 

C2H,0H  +  gg^S02 = ^^  Ho)>^^^  +  ^^^- 

With  cyclic  compounds  (p.  327)  sulphonic  acids  are  produced  with 
the  splitting  off  of  water: 

CeHe  +  H2S0,=  CfiH.-SOaH  +  H2O. 

Many  organic  bodies  are  decomposed  by  concentrated  sulphuric 
acid,  which  removes  water  from  them.  On  boiling  with  concentrated 
sulphuric  acid  nearly  all  organic  bodies  are  completely  destroyed  (p.  311). 

Nitric  acid  acts  upon  the  alcoholic  hydroxyl  groups  in  the  same  man- 
ner as  it  does  the  hydroxyl  groups  of  the  metals:  C2H5-OH  +  HN03= 
C2H5-NO3  +  H2O.  On  aromatic  bodies  it  acts  in  replacing  one  or  more  H 
atoms  by  NOV-CeHg  +  HNOa^CeHgNOg  +  HaO.  In  many  cases  nitric 
acid  has  an  oxidizing  action  when  often  a  part  of  the  carbon  is  converted 
into  oxalic  acid  or  carbon  dioxide. 

Nascent  hydrogen  (sodium  amalgam  or  aluminium  amalgam,  p.  243, 
4- water)  has  a  reducing  action  whereby  a  simple  addition,  a  removal  of 
oxygen,  or  both  simultaneously,  may  take  place:  C6H5N02  +  6H= 
CgHgNHg  +  2H2O.  Hydrogen  removes  chlorine,  bromine,  and  iodine  from 
chlorine,  bromine,  and  iodine  substitution  products  and  replaces  them  'so 
that  the  original  compound  is  regenerated  in  this  way. 

Sulphuretted  hydrogen,  ammonium  sulphide,  tin,  or  tin  chloride  and 
hydrochloric  acid,  zinc  powder  and  caustic  alkali,  zinc,  or  iron  with  acids, 
also  HI,  have  a  similar  reducing  action  as  hydrogen. 

Alkali  hydroxides  decompose  the  esters  or  compound  ethers  in  watery 
or  alcoholic  solutions: 

C^HrC^HA  +  KOH-QH.OH     +       C2H3KO2. 

Ethyl  acetate.  Ethyl  alcohol.      Potassiiun  acetate. 


ACTION  OF  HEAT.  323 

Alkyl  halogens,  etc.,  give  hydroxyl  derivatives  with  watery  solutions 
of  caustic  alkalies :    C^H^Cl  +  KOH  =  C^H^OH  +  KCl. 

Alcoholic  caustic  alkali  splits  off  all  halogen  atoms  as  halogen  hydrogen 
compounds :  CH^Cl-CHg  +  KOH =CH2=CH2  +  KCl  +  Hp. 

Solid  caustic  alkali  when  fused  with  organic  bodies  oxidizes  theuK  in 
that  O  is  substituted  for  Hg,  and  this  last  set  free:  C2H50H  +  KOH  = 
C2H3KO2  +  4H.  Often  complicated  molecules  are  thereby  split  into 
several  simpler  ones: 

CeH.^Oe  +  6NaOH  =  SC^Na^O,  +  18H. 

Dextrose.  Sodium  oxalate. 

Phosphorus  trichloride  and  phosphorus  tribromide  replace  the  hy- 

30, 


droxyl  groups  by  chlorine  or  bromine  respectively:    3C2H5OH  +  PCI3 
,HcCl  -f-  HoPOo. 


Phosphorus  pentasulphide  replaces  the  oxygen  of  the  hydroxyl  by 
sulphur: 

5CA0H  +  P^Sg-  5C2H5SH  +  P2O5. 

Water  combines  directly,  or,  as  is  generally  the  case,  on  heating  under 
pressure  it  causes  a  splitting  (saponification  or  hydrolysis,  which  see). 

2.  Action  of  Heat. 

If  non-volatile  organic  substances  are  heated  in  the  absence  of 
air  (dry  distillation)  their  elements  regroup  themselves  so  that  besides 
carbon  monoxide,  carbon  dioxide,  water,  etc.,  a  large  number  of  or- 
ganic compounds  of  simpler  composition  are  produced  and  carbon 
remains  behind.  The  large  number  of  volatile  compounds  thus  pro- 
duced can  be  in  part  condensed  by  cooling  apparatus,  the  other  part 
remaining  in  the  gaseous  state.  That  portion  which  is  condensed 
consists  of  two  layers,  a  watery  layer  which  contains  various  bodies 
in  solution  and  another  generally  dark  layer,  which  is  called  the  tar. 
Other  compounds  which  are  volatile  without  decomposing  at  certain 
temperatures  are  decomposed  with  the  deposition  of  carbon  when 
they  are  passed  in  the  gaseous  state  through  red-hot  tubes. 

In  the  dry  distillation  of  brown  and  anthracite  coal,  etc.,  bituminous 
shale  and  peat  (as  in  the  fabrication  of  illuminating-gas),  street  gas,  ammo- 
niacal  liquor  (p.  148),  tar  and  coke  are  obtained  as  decomposition  products. 
The  street  gas  contains  volatile  hydrocarbons  of  the  methane,  ethylene, 
acetylene,  and  aromatic  series  as  well  as  some  carbon  dioxide,  carbon 
monoxide,  ammonia,  air,  and  vapor  of  water,  and  when  imperfectly  puri- 
fied, also  sulphuretted  hydrogen  and  sulphur  dioxide  (see  Potassium  Ferro- 
cyanide). 

Coal-tar  is  a  mixture  of  many  constituents  which  may  be  separated  by 
fractional  distillation  and  may  be  divided  into  the  following  four  groups, 
according  to  their  chemical  behavior : 

a.  The  hydrocarbons.     These  form  the  chief  constituent,  are  indiffer- 


324  ORGANIC  CHEMISTRY. 

ent,  that  is,  are  not  soluble  in  acids  or  bases,  and  belong  chiefly  to  the 
cyclic  compounds  (p.  327). 

b.  The  phenols  torm  the  second  greatest  portion  of  coal-tar,  are  soluble 
in  alkalies  but  insoluble  in  dilute  acids. 

c.  Basic  nitrogenous  bodies.  These  occur  to  a  small  extent;  hence 
their  preparation  from  coal-tar  is  not  practical.  They  are  soluble  in 
acids  but  insoluble  in  alkalies,  and  belong  to  the  cycUc  compounds  (p.  327). 

d.  In  the  fractional  distillation  of  coal-tar  a  black  viscous  mass  re- 
mains called  tar  asphalt,  which  is  used  in  making  tar-paper,  etc. 

In  the  dry  distillation  of  wood  the  same  gases  are  obtained  as  in  the 
distillation  of  coal,  but  a  watery  fluid  which  contains  chiefly  acetic  acid, 
wood-alcohol  (methyl  alcohol),  acetone,  and  wood-tar,  which  consists 
chiefly  of  phenols,  creosote,  paraffines,  while  charcoal  remains.  Pix 
liquida,  officinal  wood-tar,  is  obtained  on  the  dry  distillation  of  coniferous 
trees,  while  aqua  picis  is  obtained  on  shaking  this  with  water. 

The  black  tough  product  remaining  after  the  fractional  distillation 
of  wood-tar  is  called  pitch. 

By  the  dry  distillation  of  bituminous  shale  containing  petrified  fishes, 
occurring  in  Tyrol,  an  oily  fluid  is  obtained  which  contains  about  11  per 
cent,  combined  sulphur.  "  On  treating  this  oil  with  sulphuric  acid  ich- 
thyol  sulphonic  acid,  C28H3eS(S03H)2,  is  formed,  whose  ammonium  salt, 
ichthyol,  has  found  use  in  medicine.     Both  bodies  are  brown  liquids. 


3.  Action  of  Ferments. 

Ferments  are  those  nitrogenous  organic  bodies  which  under  certain 
circumstances  have  the  power  of  causing  by  their  simple  presence 
chemical  transformation  in  certain  organic  compounds  without 
themselves  suffering  any  decomposition  (catalysators,  p.  66).  They 
are  divided  into  organized  and  unorganized  ferments. 

The  unorganized  ferments  or  enzymes  are  compounds  closely 
related  to  the  proteid  bodies  and  will  be  discussed  with  these.  They 
are  secreted  from  the  organized  ferments  and  are  therefore  the 
cause  of  their  action,  or  they  are  a  product  of  living  cells;  for  exam- 
ple, the  cells  of  the  saUvary  glands,  the  pancreas,  etc.  They  can 
only  transform  a  certain  quantity  of  the  decomposable  body,  and 
their  action  consists  of  a  hydrolytic  cleavage,  i.e.,  it  takes  place 
with  the  taking  up  of  the  elements  of  water  (p.  87). 

The  formed  or  organized  ferments  are  low  fungi  of  which  a  small 
number  are  sufficient  to  transform  a  large  amount  of  the  decom- 
posable body,  as  they  rapidly  increase  in  number  at  the  same  time 
that  they  cause  the  cleavage  processes.  In  order  that  they  shall 
multiply  and  be  active  the  presence  of  organic  nitrogen  and  inorganic 
salts  is  necessary.    Their  action  depends  presumably  upon  the  produc- 


ACTION  OF  FERMENTS.  325 

tion  of  enzymes;  still  only  a  few  have  been  isolated  up  to  the  present 
time. 

The  cleavage  of  organic  substances  into  simpler  ones  by  the  aid 
of  organized  ferments  is  called  fermentation  in  the  broad  sense  and 
includes  the  processes  of  fermentation  of  varieties  of  sugar,  putre- 
faction, decay,  and  acetic  acid  fermentation,  etc.  In  these  processes 
we  are  also  producing  hydrolytic  cleavages  (p.  87),  and  generally 
also  oxidations,  if  oxygen  is  present. 

Of  the  fungi  causiDg  these  processes  the  Saccharomyces  bring  about 
feinientation,  the  Schizomycetes  putrefaction,  and  the  molds  decay. 
For  the  practice  of  fermentation  it  is  important  to  know  that  the 
Schizomycetes  grow  only  in  acid-free  solutions,  the  Saccharomyces  in  0.5 
per  cent,  acid,  and  the  molds  only  in  5  per  cent.  acid. 

The  general  conditions  for  fementation  are  as  follows: 

Presence  of  air  as  carrier  of  the  germs.  If  the  decomposition  has 
begun,  then  the  further  supply  of  air  is  not  necessary. 

Presence  of  water. 

Temperatures  above  0°  and  below  100°,  as  at  0°  the  organisms  cannot 
develop  and  at  100°  they  are  nearly  all  destroyed.  Each  kind  of  fer- 
mentation takes  place  best  between  certain  temperature  limits,  which 
differ  for  each  one. 

Absence  of  anti-fermentive  and  anti-putrefactive  agents,  such  as 
arsenious  acid,  chlorine,  metallic  salts,  salicylic  acid,  xanthogenates, 
sulphur  dioxide,  carbon  disulphide,  tannic  acid,  carbolic  acid,  creosote, 
thymol,  etc.,  which  have  an  antiseptic  or  anti-zymotic  action.  Alcohol, 
common  salt,  sugar,  also  belong  to  this  group  in  that  they  remove  the 
water  necessary  for  the  decomposition. 

Putrefaction  is  the  fermentation  of  certain  organic  substances  (espe- 
cially protein  bodies  and  substances  related  thereto)  with  the  development 
of  volatile,  disagreeable-smelling  bodies.  Putrefactive  bodies  are  in  general 
the  same  as  the  decomposition  products  obtained  by  the  action  of  acids 
or  alkalies  on  the  substances  in  question. 

Fermentation  in  a  narrow  sense  or  real  fermentation  is  the  destruc- 
tion of  sugars  by  the  action  of  ferments.  We  have  various  kinds,  de- 
pending upon  the  products,  e.g.,  alcoholic,  butyric  acid,  lactic  acid,  and 
mucilaginous  fermentation. 

The  sugars  when  pure  are  un fermentable,  but  they  are  split  into  sim- 
pler compounds  by  the  action  of  organized  ferments  when  the  general 
conditions  given  above  are  observed;  also  certain  dilution  of  solution, 
and  when  protein  substances  and  inorganic  salts  are  present.  This  is  the 
reason  why  fruit-juices  containing  sugar  undergo  fermentation  when 
exposed  to  the  air,  from  which  they  take  up  the  fungi  spores.  Pure 
sugar  solutions  and  concentrated  (evaporated)  fruit-juices  containing 
sugar  do  not  undergo  this  fermentation. 

Decay  is  the  gradual  oxidation  (p.  119)  by  means  of  the  atmospheric 
oxygen  of  the  intermediary  products  produced  in  putrefaction  and  their 
conversion  into  final  products,  carbon  dioxide,  water,  and  ammonia, 
and  eventually  nitric  acid  (p.  161).     If  putrefaction  takes  place  in  the 


326  ORGANIC  CHEMISTRY. 

absence  of  air,  then  masses  rich  in  carbon  always  remain,  while  if  the 
process  takes  place  in  the  presence  of  air  (although  often  after  a  very- 
long  period),  the  substance  disappears  entirely  and  it  decomposes  com- 
pletely into  carbon  dioxide,  water,  and  ammonia. 

Mouldering  is  the  very  slow  decomposition  of  the  products  pro- 
duced in  putrefaction  which  takes  place  in  the  presence  of  a  very  small 
supply  of  air,  when,  on  account  of  the  lack  of  oxygen  the  hydrogen 
unites  in  part  with  the  carbon  forming  marsh-gas. 

Humus  substances  are  those  brown  or  black  uncrystallizable  bodies 
which  are  formed  before  the  final  products,  water,  carbon  dioxide,  and 
ammonia,  in  the  decay  and  destruction  of  plant  and  animal  bodies  as  well 
as  by  the  action  of  strong  acids  or  alkalies  upon  carbodydrates  (sugar, 
starch,  etc.).  They  are  odorless  and  tasteless  and  actively  absorb  moisture 
and  ammonia  from  the  air,  and  hence  are  important  food  for  the  plants. 
The  carbohydrates  seem  to  be  closely  related  to  many  humus  substances. 

Humus  substances  are  found  in  the  upper  layers  of  arable  soil,  in 
peat,  in  brown  coal,  in  decomposing  wood,  in  many  spring-waters,  and 
the  yellowish-brown  sediment  from  many  waters,  etc.  Some  of  these  sub- 
stances contain  nitrogen  and  are  weak  acids,  and  can  be  extracted  by 
dilute  caustic  alkalies  and  in  part  reprecipitated  from  the  brown  solu- 
tion thus  obtained.  Little  is  known  in  regard  to  the  chemical  proper- 
ties of  these  substances.  They  are  called  humin,  C40H30O15,  ulmin, 
CgoHijOy,  huminic  acid,  CgoHijOj,  ulminic  acid,  C^^^f)^,  geinic  acid, 
C20H12O7,  quellic  acid,  CigHjgOg. 

CLASSIFICATION. 

The  carbon  compounds  may  be  divided  into  the  following  classes 
according  to  their  constitution  (p.  297): 

1.  Aliphatic  compounds  are  those  whose  molecules  contain  only 
open  atomic  chains  of  C  atoms,  or  of  C  atoms  and  other  atoms  (p.  298, 
Figs.  1  and  2). 

The  aliphatic  compounds  or  fatty  bodies  are  so  called  because  the 
animal  and  plant  fats  (aXeicpa^,  fat)  belong  to  this  group.  They  are 
also  called  acyclic  or  catenic  compounds  as  they  contain  open  atomic 
chains,  and  methane  derivatives  because  they  may  be  considered  as 
derived  from  methane,  CH4,  by  substitution. 

2.  IsocarhocycUc  compounds  are  those  whose  molecules  contain 
ring-shaped  closed  atomic  chains  (atomic  ring)  which  consist  only 
of  C  atoms.  They  are  also  called  homocarbocyclic  or  in  short  carbo- 
cyclic  compounds. 

3.  Heterocarbocyclic  compounds  are  those  whose  molecules  con- 
tain ring-shaped  closed  atomic  chains,  but  which  contain  one  or  more 
polyvalent  atoms  besides  the  C  atoms  (p.  298,  Figs.  5  and  6). 

We  also  know  of  aliphatic  compounds  which  contain  closed  chains 
composed  of  various  elements;  thus  ethers,   ureids,   lactones,  lactides 


CLASSIFICATION.  327 

contain  these,  although  they  have  only  slight  similarity  with  the  hetero- 
carbocvciic  compounds.  The  iso-  and  heterocarbocychc  compounds 
(  =  cyclic  compounds)  formerly  bore  the  general  name  aromatic  com- 
pounds or  benzene  derivatives,  as  many  of  the  compounds  belonging  to 
this  class  have  an  aromatic  odor,  or  because  they  can  be  considered  as 
derived  from  benzene,  CoHg,  by  substitution. 

4.  Alicyclic  compounds  are  those  compounds  which  in  chemical 
properties  stand  between  the  aliphatic  and  the  cyclic  compounds 
and  contain  also  ring-shaped  closed  atomic  chains  which  are  com- 
posed only  of  C  atoms,  or  of  C  atoms  and  other  atoms.  But  as  in 
the  cyclic  compounds  the  C  atoms  of  the  ring  occur  with  only  one  free 
valence,  in  the  ahcycHc  compounds  one  or  all  of  the  C  atoms  of  the 
ring  may  exist  with  two  free  valences  (p.  298,  Fig.  3).  In  the  fol- 
lowing pages  the  alicyclic  compounds  will  not  be  treated  as  a  special 
class,  but  be  discussed  with  the  aliphatic,  iso-  or  heterocarbocychc 
compounds  from  which  they  are  derived. 

5.  Compounds  of  unknown  constitution.  These  diminish  more  and 
more  as  the  science  of  chemistry  advances,  and  are  included  in  the 
following  pages  with  the  compounds  of  known  constitution,  as  their 
constitution  has  been  sufficiently  elucidated  so  that  they  can  be 
classified  in  one  of  the  four  above-mentioned  classes. 


I.    ALIPHATIC  COMPOUNDS. 


CONSTITUTION. 


All  carbon  compounds  whose  molecule  contains  open  chains  of  C 
atoms  (or  of  C  atoms  and  other  atoms)  belong  to  the  aliphatic  series : 

CHj-CHrCH,,  CH2=CH-CH3,  CH3-CO-CH3,  etc., 

still  other  compounds  with  ring-shaped  grouping  of  the  atoms  will  also 
be  discussed,  these  latter  being  directly  derived  from  the  aliphatic 
compounds  and  are  called  alicyclic  compounds  (see  p.  327). 

NOMENCLATURE. 

Hydrocarbons.  The  saturated  hydrocarbons  have  the  termina- 
tion ane  and  from  CJi^^  are  designated  by  the  Greek  numerals. 
The  unsaturated  hydrocarbons  correspond  to  the  radicals  with  even 
valences  and  have  the  same  names  (see  below). 

Radicals.  The  unsaturated  atomic  groups  which  occur  unchanged 
in  a  large  number  of  compounds  are  called  radicals.  The  most 
important  radicals  are  those  derived  from  the  saturated  hydrocarbons 
CH4,  CjHg,  etc.  (p.  297) .  If  one  or  more  hydrogen  atoms  are  abstracted 
from  these,  we  obtain  radicals  with  different  valences  which  unite 
either  with  atoms  or  groups  of  atoms  until  the  limit  compound 
CfjHjr^+j  is  reached.  Thus  if  one  H  is  abstracted  from  ethane,  CzHj, 
then  the  monovalent  radical  C2H5  remains,  while  if  two  H  are  removed 
we  obtain  the  divalent  radical  C2H4,  and  if  three  H  atoms  are  taken 
away  the  trivalent  radical  C^Hg  remains,  etc. 

The  radicals  are  designated  as  follows : 
Saturated  hydrocarbons CH^ 

Methane. 

'  Monovalent CH3 

(Ending  in  -yl).  Methyl. 

,,  ,  Divalent CH^ 

■-S  (Ending  in  -ylene  or  -ene).    Methylene. 

Trivalent CH 

^Ending  in  -enyl  or  -ine).    Methenyl. 


C,H« 

C3H« 

C.H,„ 

Ethane. 

Propane. 

Butane. 

C3, 

C3H, 

C.H, 

Ethvl. 

Propyl. 

Bntyl. 

C.H, 

C.He 

C.H, 

Ethylene. 

Propylene. 

Butylene. 

C,H3 

C3H, 

C.H, 

Ethenyl 
(Vinyl). 

Propenyl 

Butenyl 

(Glyceryl). 

(Crotonyl) 

328 

r 


NOMENCLATURE.  329 

In  accordance  with  the  law  of  even  numbers  (p.  314)  the  radicals  with 
uneven  valence  cannot  exist  free.  If  they  are  released  from  their  com- 
pounds, they  generally  double  up  or  they  decompose : 

CH3I  +  CH3I   +   2Na  =   H3C-CH3  +  2NaI. 

2  mol.  methyl  iodide.  1  mol.  dimethyl. 

The  radicals  with  even  valences  can  exist  in  the  free  state,  when  they 
are  released  from  compounds  in  which  the  affinities  set  free  belong  to  two 
neighboring  carbon  atoms,  so  that  they  can  unite  together: 

CIH2C-CH2CI  +  2Na  =  H2C  =  CH2  +  2NaCl. 

Ethylene  chloride.  Ethylene. 

From  this  it  follows  that  the  radical  CH3-CH=  cannot  be  obtained  from 
the  compound  CH3-CHCI2  because  both  free  valences  cannot  be  united 
with  the  molecule  itself. 

These  radicals  are.  also  called  mono-,  di-,  etc.,valent  alcohol  radi- 
cals, after  their  most  important  compounds,  the  alcohols.  The 
monovalent  radicals  are  also  called  alkyl,  the  divalent  alkylene,  and 
the  trivalent  alkenyl  radicals. 

A  special  nomenclature  for  organic  bodies  can  be  based  upon 
the  radicals.  Thus  methane,  CH4,  can  be  considered  as  a  combination 
of  the  methyl  radical  with  hydrogen  and  hence  called  methyl  hydride, 
CH3-H,  methyl  alcohol,  CHg^OH,  as  methyl  hydroxide;  dichlor- 
methane,  CH,=Cl2>  ^s  methylene  chloride;  trichlormethane,  CH^Clg, 
as  methenyl  chloride,  etc. 

Among  the  monovalent  radical  we  differentiate  between  the  primary, 
secondary,  and  tertiary,  according  to  whether  the  unsaturated  C  atom  is 
united  to  one,  two,  or  three  other  C  atoms;  thus, 

CH3-CH2-CH2-CH-     CH3-CH2\(.jj_     (Qjj^>j^=Q_ 
Primary  butyl.  Secondary  butyl.      Tertiary  butyl. 

On  satisfying  the  free  valence  of  these  radicles  with  -OH,  -I,  etc.,  we 
obtain  the  nrimarv,  secondarv,  and  tertiary  compounds  (pp.  333,  334). 

The  radical  -COOH  is  called  carhoxyl,  -OCCHs)  'methoxyl,  -QiC^'R^) 
ethoxyl,  -SCCHg)  sulfmethyl,  -COH  carhinol,  etc. 

Letters  or  figures  are  added  to  the  names  of  certain  isomeric  com- 
pounds in  order  to  designate  the  position  of  certain  atoms  or  radicals 
in  the  molecule.  Thus  we  designate  the  terminal  C  atom  of  acids 
as  well  as  the  side-chain  of  cyclic  compounds  by  w  or  1,  the  one  com- 
bined therewith  by  a  or  2,  etc.,  and  the  terminal  C  atom  of  the  remain- 
ing compounds  by  a  or  1,  etc. 

Correspondingly  we  differentiate  between 


330  ORGANIC  CHEMISTRY. 

CH3-CHI-COOH  CHJ-CHrCOOH 

o-iodopropionic  acid.  ;? -iodopropionic  acid. 

CH3-CH(OH)CH(CH3)-COOH  CH2(0H)-CHrCHrC00H 

a-methyi-/?-oxy butyric  acid.  r-oxybutyric  acid. 

CH3-CH2-  CCI3  CH3-CCI2-  CH2CI  CH2CI-CHCI-CH2CI. 

a-tnchlorpropane.  a  0  /?-trich.orpropane.  a  0  T-trichlorpropane 

Optically  active  bodies  (p.  39)  are  designated  by  d-  (dextro) 
when  they  turn  the  ray  to  the  right,  by  I-  (laevo)  when  they  turn 
it  to  the  left,  and  by  i-  when  they  represent  the  inactive  modifica- 
tion. 

Amines,  amin  bases,  monamines,  are  to  be  considered  as  ammonia 
whose  H  atoms  are  entirely  or  in  part  replaced  by  alkyl  radicals  (see 
p.  329).  According  as  one,  two,  or  three  alkyls  are  introduced  we 
obtain  primary  amines  or  amid  bases,  secondary  amines  or  imid 
bases,  tertiary  amines  or  nitril  bases  (but  not  nitriles) : 

/H  /H  /H  /CJHg 

^H  \CH3  \CH3  \CH3 

Ammonia.  Methylamine     Dimethylamine.  Trimethylamine 

Diamines  are  derived  from  2  molecules  NH3,  in  which  each  NH3  mole- 
cule has  one  H  atom  replaced  by  one  valence  of  one  or  more  divalent 
alcohol  radicals  (alkylenes) ;   thus, 

HjN-C^HrNHa  NH=(C2H4)2=NH  N^  (C2H,)3^N. 

Ethylendiamine.  Diethylendiamine.  Triethylendiamine. 

The  triamines,  tetramines,  etc.,  have  an  analogous  derivation  where  each 
valence  of  one  or  more  multivalent  alcohol  radicals  are  introduced  into 
three, four,  etc.,  molecules  of  NH^;  thus,  CH3-C=  (NHg),,  ethenyltriamine, 
(CH2)6N4,  hexamethylene  tetramine. 

Nitrosamines  are  amines  in  which  an  H  atom  is  replaced  by  the  nitroso 
group  -NO;  thus,  (CH3)2=N-(NO),  dimethyl  nitrosamine. 

Nitramines  are  amines  in  which  one  H  atom  is  replaced  by  the  nitro 
group  -NO^;  thus,    CH3-NH-NO2,  methylnitramine. 

Imines,  imin  bases,  are  obtained  when  two  H  atoms  in  one  molecule  of 
ammonia  are  replaced  by  one  alkylene  radical:  CgHg^NH,  propylenimine. 

Nitriles  (not  nitril  bases,  see  above)  may  be  considered  as  ammonia 
in  which  all  three  H  atoms  are  replaced  by  an  alkenyl  radical  thus: 
(CH3~C)  — N,  or  also  as  a  combination  of  alkyl  with  the  radical  cyano- 
gen -C=N,  e.g.,  CH3-C^N,  methyl  cyanide. 


NOMENCLATURE.  331 

Oximes,  oximido  compounds,  are  to  be  considered  as  hydroxylamin, 
HjNCOH),  in  which  two  H  atoms  are  replaced  by  an  alkylene.  They  con- 
tain the  divalent  oxime  group  =N(OH),  and  are  isomeric  with  the  nitroso 
compounds,  i.e.,  the  combination  of  the  alkyls  with  the  NO  group;  hence 
they  are  also  called  isonitroso  compounds.  CH3-CH=N0H,  acetoxime,  is 
isomeric  with  CH3-CH2~NO,  nitrosoethane. 

Amidoximes  are  oximes  where  the  C  atom  connected  with  the  oxime 
group  =NOH  has  a  NH^  group  attached;  thus,  CH3--C(NHa)=N0H, 
ethenylamidoxime. 

Hydroximic  acids  and  hydroxamic  acids  are  oximes  where  the  C  atom 
connected  with  the  oxime  group  =NOH  has  a  -OH  group  attached;  thus, 
CH3-C(0H)=N0H. 


Hydrazines  are  produced  when  the  hydrogen  of  hydrazin,  H2N-NH3 
(p.  151),  is  replaced  by  alkyls;  thus,  (CH,)HN-NH„  methyl  hydrazin, 
(CH3),N-NH2,  dimethyl  hydrazin. 


Hydrazones  may  be  considered  as  hydrazines  in  which  two  H  atoms 
are  replaced  by  an  alkylene;  thus,  (CH3)HN-N=(CH-CH3). 

Ammonium  bases  are  to  be  considered  (although  not  proven)  as 
ammonium  hydroxide  NH4-OH,  in  which  four  H  atoms  are  substi- 
tuted by  alkyls;  thus,  (CH3)4N-OH=tetramethyl  ammonium  hy- 
droxide. 

Metallic  organic  compounds  are  those  compounds  obtained  by 
the  combination  of  metals  with  the  alcohol  radicals: 

I  II  IV  V 

NaCH3        HgCCHg)^        l^h{m,),        Sb(CH3)5 

Alcohols  are  hydrocarbons  in  which  one  or  more  H  atoms  are 
replaced  by  the  hydroxyl  group  ~0H.  According  to  the  number  of 
hydfoxyls  they  are  called  monatomic,  diatomic,  triatomic  alco- 
hols, etc.: 

C3H7(OH)  propyl  alcohol       =  Monatomic  alcohol. 
C3H6(0H)2  propylene  alcohol  =  Diatomic  ' ' 

C3H5  (OH) 3  propenyl  alcohol   =  Triatomic        " 

As  bodies  containing  more  than  one  ~0H  united  to  one  C  atom 
are  unstable,  we  know  only  of  diatomic  alcohols  with  at  least  2  carbon 
atoms,  etc.: 

The  alcohols  may  also  be  considered  as  compounds  of  the  alcohol 
radicals  with  hydroxy  Is — each  according  to  their  atomicity — mono-,  di-, 
tri-,  etc.,  or  as  metallic  hydroxides  m  which  the  metal  is  replaced  by 
the  alcohol  radicals: 

K(OH),    C3H,(0H),    Ca(0H)2,    C3He(OH)2.    A1(0H)3,    C3H,(OH)3. 

As  the  metallic  hydroxides  combine  with  acids  with  the  elimination  of 
water,  forming  neutral  or  acid  salts,  so  also  do  the  alcohols  (see  Esters  and 
Ester  Acids,  p.  332). 


332  ORGANIC  CHEMISTRY. 

Ethers  are  the  anhydrides  of  the  alcohols  and  are  formed  by  the 
removal  of  HjO  from  their  hydro xyl  groups;  thus,  2C^H5~OH  (ethyl 
alcohol)  =H20+C2H5-0-C2H5  (ethyl  ether). 

As  the  metallic  oxides  are  obtained  from  the  metallic  hydroxides 
by  the  abstraction  ot  water,  so  also  may  ethers  be  obtained  from  the 
alcohols  by  abstraction  of  water.  As  in  the  anhydride  formation  two 
molecules  of  hydroxide  of  a  monovalent  metal  are  necessary,  so  also 
with  the  hydroxides  of  monovalent  radicals  two  molecules  are  neces- 
sary, while  with  the  hydroxides  of  divalent  metals  or  radicals  water 
can  be  abstracted  from  one  molecule: 

2K0H=  K2O  +  HOH,  2CH30H=  {Cii,),0  +  HOH, 

Ca(OH)2=CaO  +  HOH,  C2H,(OH)2=  C^H.O  +HOH. 

The  ethers  may  also  be  considered  as  the  oxides  of  the  alcohol  radi- 
cals; thus,  C2H5-O-C2H5,  ethyloxide,  C2H4=0,  ethylene  oxide. 

They  may  be  considered  as  metallic  oxides  whose  metals  are  replaced 
by  equivalent  alcohol  radicals: 

C2H5-OH,  ethyl  alcohol,        corresponds  to  K-OH. 

C2H5-O-C2H,,  ethyl  ether,  "  "  R-Q-K. 

C2H4(OH)2,        ethylene  alcohol,  "  "  Ca(0H)2. 

C2H,=0,  ethylene  ether,  "  "  Ca=0. 

The  ethers  of  monatomic  alcohols  may  be  considered  as  alcohols 
in  which  the  H  atom  of  the  hydroxyl  group  is  replaced  by  an  alcohol 
radical. 

Ethers  with  two  similar  alcohol  radicals  are  called  simple,  while 
those  with  two  different  radicals  are  called  mixed  ethers.  These 
latter  are  the  anhydrides  of  two  different  alcohols;  thus,  CHg^OH 
(methyl  alcohol)  +  C3H7OH  (propyl  alcohol)  =  HOH +CH3-O-C3H7 
(methyl  propyl  ether). 

Mercaptans,  thioalcohols,  thiols,  are  those  organic  compounds 
which  correspond  to  the  hydrosulphides  of  the  metals;  thus,  CH3-SH, 
methyl  mercaptan,  corresponds  to  K-SH.  They  are  the  sulphur 
alcohols,  and  their  metallic  derivatives  are  called  mercaptides;  thus, 
(CH3S)2Hg,  mercuric  mercaptide. 

Sulpethers,  thioethers,  are  related  to  the  mercaptans  in  the  same 
way  as  the  ethers  to  the  alcohols  or  the  hydrosulphides  of  the  metals 
to  the  sulphides: 

2K-HS  ^K^S+H^S;  2CH3-SH  =  (CH3)2S+H,S. 

Esters,  compound  ethers,  correspond  to  the  neutral  salts  of  the 
metals. 

Ester  acids,  acid  esters,  ether  acids,  correspond  to  the  acid  salts 
of  the  metals. 


NOMENCLATURE,  333 

Both  are  formed  by  the  replacement  of  the  replaceable  hydrogen 
of  inorganic  or  organic  acids  (p.  335)  by  alcohol  radicals  according 
as  all  or  a  part  of  the  replaceable  hydrogen  of  the  acid  is  replaced, 
just  as  in  the  formation  of  salts.  Thus  monobasic  acids  yield  only 
esters,  while  multibasic  acids  yield  both  esters  and  ester  acids: 


KOH          + 

HCl 

= 

KCl                 + 

Hp. 

C^H^OH     + 

HCl 

= 

C^H^Cl            + 

H2O. 

Ethyl  alcohol. 

Ethyl  chloride. 

KOH          + 

H,SO, 

= 

KHSO,              + 

H,0. 

C^HjOH     + 

H,SO, 

= 

C^Hg-HSO,     + 

H2O. 

Ethyl  alcohol. 

Ethyl  sulphuric  aci( 

i. 

K,0           + 

H,SO, 

= 

K^SO,              + 

H^O 

(C,H,),0    + 

H,SO, 

= 

iC,-R,),SO,       + 

H2O. 

Ethyl  ether. 

Ethyl  sulphate. 

Isomeric  Alcohols,  Aldehydes,  Ketones.  The  isomeric  alcohols 
are  divided  into  primary,  secondary,  and  tertiary  according  to  their 
chemical  behavior,  due  to  the  position  of  the  HO  groups. 

We  have  seen  (p.  302)  that  in  the  substitution  of  one  H  atom  by 
a  univalent  element  or  radical  in  propane,  CgH^,  two  isomers  are 
possible,  namely,  CHg-CH.-CH.lOH)  and  CH3-CH(OH)CH3;  also  that 
from  the  two  butanes,  C4H10,  four  isomeric  substitution  products  are 
possible;  in  other  words,  that  by  the  substitution  of  one  OH  group 
in  place  of  one  H  atom  tlie  existence  of  two  or  of  four  alcohols,  respect- 
ively, are  made  possible.  These  four  alcohols  are  known,  and  the  struc- 
ture given  on  page  302  corresponds  in  fact  to  their  chemical  behavior. 

Primary  alcohols  by  oxidation  are  converted  into  aldehydes 
(from  alcohol  dehydrogenatus)  by  the  removal  of  two  intraradical  hy- 
drogen atoms  (belonging  to  the  alcohol  radicals).  On  further  action 
the  aldehydes  take  up  one  O  atom  very  readily  and  are  converted 
into  acids  (p.  335).  Each  primary  alcohol  has  a  corresponding  alde- 
hyde and  an  acid  with  the  same  number  of  C  atoms;    thus. 

Methyl  alcohol,     CH4O+  O  =  H2O+  CH2O,  Methyl  aldehyde. 
Methyl  aldehyde,  CH2O+  O  =  CH2O2,  Formic  acid. 

This  behavior  can  be  explained  if  we  admit  that  in  the  primary 
alcohols  one  hydroxyl  replaces  one  hydrogen  atom  of  a  CH3  group 
and  hence  we  have  still  two  oxidizable  H  atoms  in  the  group;  thus, 
CH3  CH3  CH3  CH3 

CH3  H2=C0H  H-C=0  HO-C=0 

Ethane  Ethyl  alcohol.       Ethyl  aldehyde.        Acetic  acid. 


334  ORGANIC  CHEMISTRY. 

Primary  alcohols  contain  the  group  "CHjCOH). 

Aldehydes  contain  the  group  "011=0. 

Secondary  alcohols  are  isomeric  with  the  primary  alcohols,  and  by 
oxidation  they  at  first  also  lose  two  hydrogen  atoms  and  form  ketones 
which  are  isomeric  with  the  aldehydes.  On  further  oxidation  the 
ketones  yield  acids  which  contain  a  less  number  of  carbon  atoms; 
thus, 

CH3-CH(OH)-CH3+  0  =  CH3-CO-CH3+  H2O. 

Secondary  propyl  alcohol.  Propyl  ketone. 

CH3-CO-CH3+4O  =  CH3-COOH+C02+HA 

Propyl  ketone.  Acetic  acid. 

This  behavior  is  to  be  explained  by  the  fact  that  in  the  secondary  alco- 
hols the  hydroxyl  replaces  one  H  atom  of  the  ^CHg  group,  and  the  group 
'=CH(OH)  thus  produced  cannot  be  converted  into  the  CO(OH)  group 
without  the  splitting  off  of  a  neighboring  C  atom.  As  the  =CH(0H)  group 
can  exist  only  in  such  saturated  compounds  as  contain  at  least  three 
C  atoms,  then  the?  lowest  secondary  alcohol  must  contain  three  C  atoms. 

Secondary  alcohols  contain  the  group  =CH(OH). 

Ketones  contain  the  group  ~C0~,  which  is  united  to  carbon  atoms 
on  both  sides. 

Tertiary  alcohols  are  compounds,  isomeric  with  the  primary  and 
secondary  alcohols,  which  on  oxidation  are  immediately  transformed, 
without  the  formation  of  intermediate  products,  into  various  acids, 
or  ketones  and  acids,  containing  less  amount  of  carbon: 

{CB,),(C,li,)    C-OH+ 30  =  CH3-COOH+  CH3-CO-CH3+  HjO. 

Tertiary  amyl  alcohol.  Acetic  acid.  Propyl  ketone. 

They  contain  the  hydroxyl  in  the  place  of  the  H  atom  of  the  CH= 
group,  and  as  the  CH=  group  can  exist  only  in  saturated  compounds, 
which  contain  at  least  four  C  atoms,  the  lowest  tertiary  alcohol  must 
contain  four  C  atoms: 

Q^^  >  C  <  QQ    or     (CH  3) 3 = C-OH,  tertiary  butyl  alcohol. 

These  alcohols  contain  no  more  oxidizable  hydrogen  attached  to 
the  hydroxy lated  carbon,  hence  they  change  immediately  in  the  early 
stages  of  oxidation 

The  tertiary  alcohols  contain  the  group  -C"OH,  which  is  com- 
bined to  the  C  atoms  by  its  three  valences. 

Sometimes  the  isomeric  alcohols  are  considered  as  derivatives  of 
methyl  alcohol  or  carbinol,  CHa'OH,  whose  H  atoms  are  replaced  by 
alkyls  and  are  called: 

CgH^-CHj'OH,  propyl  carbinol,  primary  butyl  alcohol; 
(CH3)3=C-OH,  trimethyl  carbinol,  tertiary  butyl  alcohol; 
(C2H5)(CH3)=CH'OH,  methyl  ethyl    carbinol,  secondary  butyl   alcohol. 


NOMENCLATURE,  335 

Acids  are  formed  on  the  oxidation  of  primary  alcohols,  when 
the  two  hydrogen  atoms  which  are  united  with  the  hydroxyl  group 
to  the  same  C  atom  are  replaced  by  an  0  atom,  or  when  an  oxygen 
atom  is  added  to  the  aldehydes  (p.  333).  The  carboxyl  group  ~COOH 
is  characteristic  of  the  acids.  All  acids  contain  two  hydrogen  atoms 
less  and  one  oxygen  atom  more  than  the  alcohols  from  which  they 
are  derived.  While  in  inorganic  acids  nearly  all  the  H  atoms  present 
are  replaceable  with  the  formation  of  salts,  with  the  organic  acids 
only  so  many  replaceable  H  atoms  are  available  in  the  formation 
of  salts  or  esters  (p.  332),  as  there  are  ~COOH  groups  present. 

The  basicity  of  organic  acids  is  dependent  upon  the  number  of 
carboxyl  groups  contained,  while  the  atomicity  is  dependent  upon 
the  number  of  hydroxyl  groups  present: 

CH3-COOH,  CH2(OH)CqOH,  HOOC-COOH, 

Acetic  acid.  Glycolic  acid.  Oxalic  acid. 

Monatomic  and  monobasic.     Diatomic,  but  monobasic.       Diatomic  and  bibasic. 

CH37COOK,  CH^COH)  -  COOK.  KOOC  -  COOK, 

Potassium  acetate.  Potassium  glycolate.  Potassium  oxalate. 

CH3-COO.  f.^^  CH,(OH)COO.  J.I  COO^" 

CHg-COO^'"^'  CH2(0H)C00^'"^'  COO^*"^' 

Calcium  acetate.  Calcium  glycolate.  Calcium  oxalate. 

The  hydrogen  present  in  organic  acids  but  not  available  for  the 
formation  of  salts  or  esters  (intraradical)  may  also  be  replaced  by 
atoms  or  groups  of  atoms  whereby  the  abihty  of  the  acid  to  form 
salts,  etc.,  is  in  no  wise  changed ;  thus, 

CH2(N03)-COOH,        CH,(Nri3)7COOH,       CH2(0H)-C00H, 

Nitroacetic  acid.  Amidoacetic  acid.  Oxyacetic  acid. 

CH3(N02)-COONa,       CH2(.NH2)-COOK,       CH2(0H)-C00NH„ 

Sodium  nitroacetate.  Potassium  amidoacetate.        Ammonium  oxyacetate. 

Imido-acidsare  derived  from  the  acids  by  the  replacement  of  the  O^ 
atom  of  the  -COOH  group  by  =NH.  They  are  only  known  in  the  form 
of  their  esters,  the  imido  ethers;  thus,  CH3-C(NH)0(CH3). 

Thio-acids.  The  oxygen  of  the  COOH  groups  of  acids  can  be  replaced 
by  sulphur  and  from  these  acids  many  compounds  are  derived : 

CH3-COSH,  CH2(NH,)-C0SH,  CH3-CSSH, 

Thioacetic  acid.  Amidothioacetic  acid.  Dithioacetic  acid. 

CH3-COSK,  CHgCOSCC^Hs),  (CH3-C0),S, 

Potassium  thioacetate.  Ethyl  thioacetate.  Thioacetic  anhydride. 

Imidothio-acids  are  derived  from  the  thio  acids  by  replacing  the  =0 
atoms  of  the  -COSH  groups  by  =NH.  They  are  only  known  in  the  form 
of  esters,  the  imidothio-ethers. 


336  ORGANIC  CHEMISTRY. 

Acid  radicals,  acyls,  are  the  organic  acid  residues  united  with 
the  hydroxyl  groups,  just  as  with  the  inorganic  acids,  but  not  known 
free.  Their  name  is  formed  by  adding  yl  to  the  Latin  name  of  the 
acid;    thus, 

H-CO,  CH3C-O,  OC-CHrCO, 

Fonnyl.  Acetyl.  Malonyl. 

Acid  anhydrides  are  formed  from  the  acids  by  spUtting  off  of  HjO 
from  the  carboxyl  groups: 

2CH3-COOH  =  CH3-COO-CO-CH3+  Hp. 

Acetic  acid.  Acetic  anhydride. 

As  in  the  monobasic  inorganic  acids  two  molecules  must  join  together  in 
order  that  water  is  split  off,  so  the  same  is  true  for  the  organic  monobasic 

2HN02=N203+H20;    2CH3-COOH=(CH3CO)20  +  HA 
On  the  contrary,  one  molecule  of  water  can  be  split  off  from  multi- 
basic  inorganic  acids;    thus,   HgSOi^SOg+HgO;  so  also  many  organic 
acids  yield  the  same: 

C,H,<gggg=C,H,<^g>0  +  HA 

Succinic  acid.         Succinic  anhydride. 

The  anhydrides  of  the  monobasic  acids  are  comparable  with  the  anhy- 
drides of  the  monatomic  alcohols  (the  ethers)  in  that  the  ethers  contain 
two  alcohol  radicals  united  to  an  oxygen  atom,  while  the  acid  anhydrides 
contain  two  acid  radicals  under  the  same  conditions.  They  also  may  be 
considered-  as  acids  whose  carboxyl  hydrogen  is  replaced  by  the  same  acid 
radical  which  is  contained  in  the  acid. 

Amido^acids,  amino-acids,  glycocoUs,  are  produced  when  the 
NHj  group  (amido  group)  replaces  the  intraradical  H  atoms  of  the 
acid;  thus,  CHjCNHJ-COOH,  amidoacetic  acid. 

Acid  amides,  amides,  are  to  be  considered  as  ammonia  in  which 
the  hydrogen  is  in  part  or  wholly  replaced  by  monovalent  acid  radi- 
cals (amines,  p.  330): 

H\  H\  H\  CHgCOv 

H^N  H^N  CHgCO-^N  CHjCO^N 

H-^  CHgCO^  CH3CO/  CH3CO/. 

Ammonia.  Acetamide.  Diacetamide.  Triacetamide. 

We  differentiate  between  primary,  secondary,  or  tertiary  amides  accord- 
ing to  whether  one,  two,  or  three  H  atoms  are  replaced. 

Acid  imides,  imides,  are  produced  when  two  H  atoms  of  ammonia  are 
replaced  by  a  bivalent  acid  radical;  thus,  HN(-0C-CH2~C0-),  malonimide. 

Thiamides  are  derived  from  the  amides  by  replacement  of  S  for  O;  thus, 
CH3-CS~NH2,  thiacetamide. 

Amidines,  amimides,  are  derived  from  the  amides  by  the  replacement 
of  =NH  for  =0;  thus,  CH3-C(NH)NH2,  ethenylamidine. 


INTERNATIONAL  NOMENCLATURE,  337 

Amine  Acids,  Acid  Amides.     Among  the  polybasic  acids  there 
exist  neutral  amides  and  also  acid  amides  or  amine  acids  according 
to  whether  two  or  more  carboxyl  groups  be  present;   thus, 
.COCNH^)  .COCNH^) 

C2H4V  C2H4V 

^COOH  ^COCNH^) 

Succinaminic  acid.  Succinamide. 

In  the  amides  all  the  hjdroxyls  of  the  carboxyl  groups  are  re- 
placed by  the  amido  group,  NHj.  In  the  amine  acids  the  hydroxyls 
of  the  carboxyl  groups  are  only  in  part  replaced  by  NHj. 

Hydrazides  are  obtained  when  acid  radicals  replace  the  hydrogen  in 
hydrazin,  H^N-NHg;  thus,  HgN-NHCCHg-CO)  =  acetyl  hydrazid. 

Mixed  Compounds.  The  different  atomic  groups  which  we  have 
seen  are  characteristic  for  the  various  compounds  may  exist  simul- 
taneously in  the  same  molecule,  producing  bodies  having  mixed 
functions;  e.g.,  aldehyde  alcohols  or  aldoses  with  the  groups  CHO 
and  CH2OH  (or  CHOH  or  COH),  aldehyde  acids  with  the  groups  CHO 
and  COOH,  ketone  alcohols  or  ketoses  with  the  groups  CO  and 
CH2OH,  ketone-acids  with  the  groups  CO  and  COOH,  amido-alcohols 
with  the  groups  NHj  and  CH2OH,  etc.,  amido-ketones  with  the  groups 
NHj  and  CO,  amido-aldehydes  with  the  groups  NH2  and  CHO. 

2.  International  Nomenclature. 

This  is  used  for  the  present  only  in  the  pubhcation  of  chemical 
investigations  and  large  chemical  works.  It  is  based  upon  substi- 
tution; each  compound  is  considered  as  a  derivative  of  a  hydro- 
carbon, and  this  is  obtained  if  we  replace  all  the  other  atoms  or 
atomic  groups  present  in  the  respective  C  compound  by  the  corre- 
sponding number  of  hydrogen  atoms.  Accordingly  CHj^NOH  is 
not  called  formoxime,  but  methanoxime;  CHj^CO^NHj  not  acetamide, 
but  ethanamide;  CH3~CH2~CN  not  propionitrile,  but  propane-nitrile. 

Saturated  hydrocarbons  with  branchless  chains  terminate  in  ane;  there- 
fore we  have  only  one  butane  and  one  pentane,  etc.  Hydrocarbons  with 
branched  chains  are  to  be  considered  as  derivatives  of  normal  hydrocar- 
bons, and  their  name  is  formed  from  the  longest  normal  chain  which  the 
formula  contains  to  which  the  name  of  the  side  chain  is  added;  thus, 

pjJsXcH-CHg  is  not  called  isobutane,  but  methyl  propane; 

CH,-CH2\rtTT-r<TT  -nw    is  not  called  heptane  or  triethyl  methane,  but 
CHa-CHjj/^^^"^  ^^2     rather  ethyl  pentane. 


338  ORGANIC  CHEMISTRY. 

When  a  carbon  radical  is  introduced  into  a  side  chain,  then  we  desig- 
nate this  by  the  prefix  metho-,  etho-,  etc.,  in  place  of  methyl,  ethyl,  which 
are  only  used  in  substitution  in  the  main  chain.  Thus  the  following  hydro- 
carbon is  not  called  isopropyl  heptane,  but  methoethyl  heptane: 

The  Arabic  numerals  are  used  to  designate  which  carbon  atom  of  the 
chief  chain  has  the  side  chain  attached ;  the  numbers  beginning  at  that 
end  of  the  chief  chain  closest  to  the  side  chain;  thus, 

12345  54321 

^^^XcH-CHj-CH^-CHg    and    CH3-CH2-CH<^^][^2-CHr 

Methyl  pentane  2  and  Methyl  pentane  3. 

This  numbering  of  the  members  of  the  hydrocarbons  is  also  retained 
for  all  the  substitution  products : 

CH^Cl-CH^Cl,  cjj^CH-CH2-CH2-CH,Br. 

1 , 2-dichlorethane.  2-methyl-5-brompentane. 

Unsaturated  hydrocarbons  with  one  double  bond  have  the  final 
syllable  -ene,  with  two  -diene,  with  three  -triene,  etc. ;  for  example, 
ethene  instead  of  ethylene,  HgC^CHo,  hexadiene  instead  of  diallyl, 
CHa=CH-CH2-CH2-CH=CH2,  etc.  Hydrocarbons  with  treble  bonds  end  in 
-ine,  -diine,  -triine;  thus,  hexadiine,  H^C-C-  C-C^CHg.  If  double  and 
treble  bonds  occur  simultaneously,  we  make  use  of  the  termination  -enine 
and  -dienine,  etc.  If  necessary,  the  position  of  the  multiple  bonds  can 
be  designated  by  numbering  the  C  atom  at  which  it  occurs : 
CH3-CH=CH-CH3,  butene  2. 

Hydrocarbons  with  closed  chains  of  3,  4,  5,  6  CHj  groups,  for  instance 
tri-,  tetra-,  penta-,  hexamethylene  are  called  cyclanes  and  have  the  name 
of  the  corresponding  saturated  hydrocarbons  with  the  prefix  cyclo;  e.g., 
cyclohexane  instead  of  hexamethylene. 

Radicals.  Monovalent  radicals  end  in  -yl;  e.g.,  CH.-CH,-,  ethyl, 
CH2=CH-,  ethenyl,  CH-C-,  ethinyl. 

Radicals  with  alcohoHc  functions  end  in  -ol:  e.g.,  -CH„-CH50H, 
ethylol, -CH=CHOH,  ethenyloL 

Aldehyde  radicals  end  in  -al;  e.g.,  -CH2-CHO,  ethylal. 

Acid  radicals  have  the  termination  -oyl  added  to  the  original  hydro- 
carbon; e.g.,  CH3-CO-,  acetyl =ethanoyl. 

Alcohols  have  the  final  syllable  -ol  attached  to  the  hydrocarbon 
from  which  it  is  derived.  The  polyatomic  alcohols  have  di-,  tri-,  tetra- ,  etc. , 
added  to  the  -ol;  e.g.,  C2H5-OH,  ethyl  alcohol  =ethanol,  C2H,=(OH)2. 
glycol  =  ethandiol,  CsHj^COH)^,  glycerin  =  propantriol.  Unsaturated 
alcohols  end,  according  to  the  bonds,  in  -enol  or  -inol;  e.g., 
CH2=CH-0H,  ethenyl  alcohol =ethenol,  CH2=CH-CH20H,  propenyl 
alcohol =propenol,   HC=C-CH20H,    propargylic   alcohol =propinol,   etc. 

The  designation  enol  structure  comes  from  ethenol,  and  all  compounds 
which  like  ethenol  contain  the  =C=COH-  group  are  called  evols. 

Ethers  are  designated  by  placing  -oxy  between  the  hydrocarbons 
from  which  they  are  produced:  ethyl  ether,  (C2H5)0=ethanoxyethane, 
ethylamyl  ether=  pentaoxyethane. 


CLASSIFICA  TION.  339 

Sulphur  ethers  have  -thio,  -dithio,  and  -suljon  introduced;  eg., 
CgHj-S-CgHj,,  benzenthioethane,  CgH^-S-S-CgHj,  benzendithiobenzene, 
CgHg-SOg'Cg  H5  =  benzensulf  onbenzene. 

Aldehydes  have  the  termination  -al  attached  to  the  hydrocarbon, 
sulphaldehydes  -thiol)  for  example,  HCOH,  methanal,  CH3  CSH,  ethan- 
thial. 

Ketones  have  the  final  syllable  -on,  the  diketones,  triketones,  thio- 
ketones,  the  termination  -dion,  trion,  -thion;  e.g.,  CH.3-CO-CH3,  pro- 
panon,  CH3-CO-CH2-CO-CH3,  pentadion  2,  4. 

Acids  are  designated  by  adding  -acid,  -diacid,  -triacid  to  the  original 
hydrocarbon  with  the  ending  ic;  e.g.,  CH3-COOH,  ethanic  acid  instead 
of  acetic  acid,  CgH^CCOOH)^,  butanic  diacid  instead  of  succinic  acid  or 
with  mixed  acids  to  the  name  of  the  respective  alcohol,  ketone,  etc. ;  e.g., 
2-propanohc  acid  instead  of  ethylidene  lactic  acid,  CH3-CH0H~C00H,  3- 
propanolic  acid  instead  of  ethylene  lactic  acid,  CHg- OH-CHg^COOH, 
etc.  Thioacids  with  a  S  atom  simply  united  to  the  C  atom  are  called 
thiolic  acids;  with  doubly  united  S  atom,  thtonic  acids;  e.g.,  CHg-COCSH), 
ethanthiolic  acid,  CH3-CS(0H),  ethanthionic  acid,  CHgCSCSH),  ethan- 
thiolthionic  acid. 

Salts  and  esters  end  in  -ate;  thus,  (CH02)2Ca,  calcium  methanate 
instead  of  calcium  formate,  (€00)2X2,  potassium  ethandiate  instea(/ 
of  potassium  oxalate. 

CLASSIFICATION. 

All  aliphatic  compounds  are  formed  by  replacing  all  or  a  part  of 
the  H  atoms  of  the  limit  hydrocarbons  (see  p.  340)  by  other 
atoms  or  groups  of  atoms.  Consequently  the  aliphatic  compounds 
will  be  treated  in  the  following  pages,  according  to  the  number  of 
side  groups  they  contain,  as  compounds  of  mono-,  di-,  tri-,  etc., 
valent  alcohol  radicals  (p.  328),  or  in  short  as  mono-,  di-,  tri-,  etc., 
valent  compounds.  In  connection  with  these  compounds  we  shall 
discuss  those  compounds  which  have  a  close  genetic  relationship, 
while  the  carbohydrates  will  be  specially  discussed  in  order  to  make 
the  subject  easier. 


COMPOUNDS  OF   MONOVALENT  ALCOHOL  RADICALS. 

I.  Monovalent  Alcohol  Radicals. 

General  formula  CnH2n+i. 
They  cannot  exist  in  the  free  state  (p.  328).     If  an  atom  of  H  is 
substituted  in  the  saturated  hydrocarbons  CnH2n+2,  then  the  hydro- 
carbon residue  CnH2N4-i  behaves   Hke  a  monovalent  radical.     These 
are  called  alkyls,  specially  methyl,  ethyl,  propyl,  etc.  (p.  328),  which 


340  ORGANIC  CHEMISTRY. 

names  are  often  used  as  roots  in  the  nomenclature  of  compounds 
derived  therefrom. 

2.  Saturated  Hydrocarbons. 

Limit  Hydrocarbons  or  Paraffins. 
General  form  ClaujNH2N+2- 

Boiling-pomt.  Boiling-point. 

Methane,  CH4 - 164°  Octane,  CgH^g 124° 

Ethane,    CgHe -   93°  Nonane,  C^ti^^ 149° 

Propane,  CgHg -  45°  Decane,  C^^H^ 173° 

Butane,    C.H^o +     1°  Undecane,       Cj^H,, 195° 

Pentane,  C^U^^ 38°  Dodecane,       C,^^^ 219° 

Hexane,  CgBj^    71°  Hexadecane,  C^eHg^ solid 

Heptane,  0,11,6    99°  etc. 

Properties.  These  compounds  are  called  limit  hydrocarbons 
because  they  cannot  unite  with  any  more  atoms  or  groups  of  atoms 
(p.  297).  Their  names  end  in  -ane.  They  are  not  attacked  in  the 
cold  by  such  energetic  oxidizing  agents  as  concentrated  sulphuric 
acid  or  nitric  acid,  hence  they  are  also  called  paraffins  (parum,  with- 
out, affinis,  affinity). 

The  lower  members  are  colorless  gases,  the  middle  members 
colorless  liquids,  and  the  higher  ones  (CiiHjq  and  above)  are  colorless 
solids,  all  being  almost  or  altogether  insoluble  in  water;  the  gaseous 
members  are  somewhat  soluble  in  alcohol,  while  the  Uquids  are  readily 
soluble  therein.  The  solubility  of  the  higher  members  decreases 
as  the  amount  of  C  increases.  From  butane  on  we  find  isomeric  par- 
affins which  differ  from  each  other  in  density  and  boihng-point. 
When  ignited  they  burn  with  a  luminous  and  smoky  flame  (p.  92). 

Chlorine  has  a  substituting  action  forming  HCl  and  mono-,  di-.  tri- 
chloride, etc.,  depending  upon  the  extent  of  action;  thus,  CH4  +  2C1  =  CH3C1 
+  HC1.  Bromine  has  a  less  energetic  action.  In  regard  to  the  action 
of  iodine  see  p.  322.  Otlier  derivatives  can  be  readily  prepared  from 
the  halogen  derivatives  (p.  302). 

According  to  the  chemical  structure  two  isomers  of  butane  must 
exist,  and  the  number  of  isomers  increases  rapidly  with  the  increase  in 
the  amount  of  C  in  the  comnound  (p.  30iy  The  boiling-noint  of  the 
normally  constituted  m^^mber  is  always  higher  than  that  of  its  isomers. 

Preparation.  1.  All  may  be  constructed  from  methane;  thus  if  we 
heat  its  chloride,  bromide,  or  iodide  with  sodium  (or  zinc,  p.  348,  g").  we 
obtain  ethane:  2CHJ  +  2Na=2NaT  +  C2H6.  If  from  this  we  prepare 
CjHJ  and  heat  it  with  CH J  and  sodium,  we  obtain  the  next  hvdro- 
carbon,etc.  CFittig-Wiirtz  method):  C2H5l  +  CH3l  +  2Na=2NaI  +  C3H8; 
C3HJ  +  CH3l  +  2Na=2NaI=aH,o. 


CLASSIFICATION.  341 

2  The  fatty  acids  (p.  345)  decompose  into  carbon  dioxide  and  paraf- 
tins  by  electrolysis  or  by  heating  with  caustic  alkalies: 

CH3-COOH  +  2NaOH = CH,  +  Na.COg  +  R,0. 

^-  The^unsaturated  hydrocarbons  form  paraffins  with  nascent  hydro- 
gen:  xijO    Ctl2  +  2H  =  H3C~CH3. 

4  By  the  action  of  nascent  hydrogen  on  the  halogen  derivatives  of 
the  aliphatic  hydrocarbons: 

CHCl3  +  6H  =  CH,  +  3HCl. 

5.  By  heating  the  zinc  alkyls  (p.  382)  with  water: 

ZnCC^H,),  +  2H0H= Zn(OH),  +  2C,H„. 

6.  By  heating  the  alcohols  with  hydriodic  acid: 

CA-0H  +  2HI=C,He  +  H,0  +  I,  (p.  322). 

Formation.  They  are  obtained  in  large  quantities  in  the  dry 
distillation  of  peat,  brown  coal,  bituminous  shale.  Boghead  and 
Cannel  coal  (as  in  the  manufacture  of  illuminating-gas,  p.  323).  The 
gases  obtained  thereby  consist  of  methane,  ethane,  propane,  butane, 
besides  other  hydrocarbons.  From  the  tar  which  is  produced  at 
the  same  time  a  mixture  of  paraffins  is  obtained  by  fractional  distilla- 
tion. 

Wood-  and  coal-tar  contain,  on  the  contrary,  chiefly  aromatic 
hydrocarbons,  especially  the  solid  constituents  naphthalene  and  anthra- 
cene (which  see). 

Occurrence.  American  petroleum  consists  of  a  mixture  of  different 
paraffins;  Caucasian  petroleum  contains  chiefly  aromatic  hydro- 
carbons and  the  hydrogen  addition  products  of  the  same,  such  as  the 
naphthenes,  CnH2N.  GaHcianand  German  petroleums  stand  between 
these  two  kinds  according  to  their  composition.  In  the  gases  which 
are  evolved  at  the  petroleum  wells  and  also  dissolved  in  the  crude 
petroleum  we  find  methane  (60-90  per  cent.)  as  well  as  some  ethane, 
propane,  and  butane. 

Crude  petroleum  is  an  oily  brown  fluid  which  loses  its  volatile  con- 
stituents on  standing  in  the  air,  becomes  thicker,  and  finally  forms 
the  natural  asphalt.  From  American  crude  petroleum  by  fractional 
distillation  various  hydrocarbons  are  separated  into  the  following  groups: 

Petroleum  ether,  ligrcin,  consists  of  pentane  and  hexane  and  distils 
at  40°-70°  as  a  colorless  liquid.  ,         . 

Gasoline  (low  and  high  boiling-point)  is  used  for  making  illuminating- 
gns,  for  heating  purposes,  and  when  vaporized  and  mixed  with  air  explodes 
with  force;   hence  it  is  used  as  a  motive  force.  ^    ^  ^ 

Benzine  consists  of  hexane,  heptane,  and  octane,  distils  at  50  -120  , 
and  is  soluble  in  5-6  parts  alcohol. 


342  ORGANIC  CHEMISTRY. 

Refined  petroleum,  kerosene,  contains  the  paraffins  distilling  between 
150°  and  300°.  The  vapors  should  not  ignite  when  heated  below  38° 
(100°  F.),  otherwise  the  oil  contains  paraffins  having  a  lower  boiling- 
point  and  may  explode  if  burned  in  a  lamp. 

Vulcan  oil.  Lubricating  oil  is  the  thick,  impure  constituent  distilling 
above  300°,  and  is  used  as  a  lubricant. 

Parafl^  oil,  vaseline  oil,  obtained  from  the  vulcan  oil  by  decoloriza- 
tion  with  animal  charcoal,  is  a  colorless  oily  liquid,  contains  the  paraf- 
fins distilling  above  360°,  and  is  used  in  the  preparation  of  paraffin 
salves. 

Vasogene,  vasol,  is  a  mixture  of  paraffin  oil  and  ammonium  oleate 
which  serves  as  a  basis  for  salves. 

Vaseline,  petrolatum,  mineral  fat,  is  the  name  given  to  the  product 
obtained  by  purifying  the  residues  from  the  petroleum  distillation.  It 
forms  a  yellow  or  colorless  soft  mass  which  melts  at  32°-35°,  and  is 
used  as  a  substitute  for  fats,  as  it  does  not  become  rancid. 

Solid  paraffins.  Ordinarily  only  the  solid  limit  hydrocarbons  are 
called  paraffins.  They  occur  comparatively  pure  in  the  mineral  kingdom 
as  mineral  wax,  ozocerite,  and  can  also  be  obtained  from  that  portion 
of  American  and  Indian  petroleum  which  has  the  highest  boiling  by  cooling 
strongly,  as  well  as  from  the  various  kinds  of  tar.  These  crude  paraffins 
are  freed  from  foreign  constituents  by  means  of  sulphuric  acid  and  de- 
colorized by  animal  charcoal,  and  occur  in  commerce  as  white  opalescent 
or  crystalline  masses  which  melt  between  40°  and  80°  and  then  called 
paraffin,  ceresin,  belmontin,  and  are  used  chiefly  in  the  manufacture  of 
candles. 

3.  Monohydric  Alcohols. 

General  formula  CxH2n+iOH. 

Methyl  alcohol,  CH3OH.  Nonyl  alcohols,  C«H,jOH. 

Ethyl  alcohol,  C2H5OH.  Decyl  alcohols,  CioH^iOH. 

Propyl  alcohols,  C3H7OH.  Dodecyl  alcohols,  Ci2H250H. 

Butyl  alcohols,  C^HgOH.  Tetradecyl  alcohols,  C^JlJdU, 

Amyl  alcohols,  CgHi^H.  Cetyl  alcohol,  CieHggOH. 

Hexyl  alcohols,  CeHigOH,  Ceryl  alcohol,  C27H55OH. 

Heptyl  alcohols,  C7H15OH.  Melissyl  alcohol,  CgoHe^OH 

Octyl  alcohols,  CgHi^OH.  etc. 

Properties.  The  lower  members  are  colorless  fluids  soluble  in 
water,  while  the  intermediate  members  are  less  soluble  in  water  and 
have  an  alcoholic  or  fusel-oil  odor  and  a  burning  taste.  The  members 
from  CijHjjO  and  above  are  sofids,  insoluble  in  water  and  mostly 
without  taste  or  odor. 

Above  propyl  alcohol  we  have  isomeric  alcohols  which  are  differ- 
entiated by  their  behavior  on  oxidation  and  by  their  varjdng  boil- 


CLASSIFICATION.  343 

ing-points  and  are  called  primary,  secondary,  and  tertiary  alcohols 
(p.  333). 

All  alcohols  are  neutral  in  reaction,  but  behave  Hke  bases  in  that 
they  combine  with  acids  forming  salt-like  combinations  which  are 
called  esters  or  ester-acids  (p.  332). 

Halogens  do  not  have  a  substituting  action  upon  the  alcohols, 
but  an  oxidizing  action  instead: 

C2H5OH+ 2C1  =  C2H,0+  2HC1. 

On  treatment  with  HCl,  HBr,  and  HI  or,  better,  with  the  halogen 
derivatives  of  phosphorus,  the  alcohols  yield  simple  chlorine,  bromine, 
or  iodine  derivatives  of  the  hydrocarbons  (p.  332). 

The  alcohols  form  crystalline  compounds  with  CaClj,  which  decom- 
pose again  with  water  (p.  349). 

The  alcohols,  like  water,  are  acted  upon  by  the  alkali  metals  with 
the  evolution  of  hydrogen,  and  crystalline  m.etallic  alcoholates  are 
obtained  which,  decompose  with  water  into  alcohol  and  alkali  hy- 
droxide, and  readily  give  up  the  metal  for  other  monovalent  elements 
or  radicals: 

HO-H+Na  =  Na-OH+H; 

CH3-OH+ Na  =  CH3-0Na+ H ; 

CH3-0~Na+  CH3I  =  CH3-O-CH3+  Nal. 

As  only  one  H  atom  is  replaceable,  this  one  must  have  a  different 
position  from  the  other  H  atoms. 

On  heating  primary  and  secondary  alcohols  with  concentrated 
sulphuric  acid  they  are  converted  into  their  anhydrides,  the  ethers 
(p.  332). 

This  process  must  not  be  considered  as  simply  an  abstraction  of  water 
by  means  of  the  sulphuric  acid  (see  Ethyl  Ether). 

On  heating  with  an  excess  of  concentrated  sulphuric  acid  or  other 
dehydrating  bodies  the  divalent  hydrocarbons  are  obtained :  C2H5OH  =• 
CjH.+  H^O. 

The  primary,  secondary,  and  tertiary  alcohols  behave  on  oxidation 
as  described  on  p.  334. 

Occurrence.  Various  alcohols  are  found  in  nature  in  the  ethereal 
oils  and  waxes,  seldom  free,  but  generally  as  esters. 

Formation.  Ethyl  alcohol  and  certain  of  its  homologues  are 
produced  in  the  fermentation  of  grape-sugar. 


344  ORGANIC  CHEMISTRY. 

Preparation  of  Primary  A  Icohols.     1 .  The  primary  alcohols  are  obtained 
by  the  action  of  nascent  hydrogen  upon  the  aldehydes: 

CH3-CH2-COH  +  2H= CHg-CH^-CH^COH). 
Propyl  aldehyde.  Propyl  alcohol. 

2.  By  the  action  of  moist  silver  oxide  (also  by  KOH)  on  the  halogen 
mono-substitution  derivatives  of  the  hydrocarbons: 

C5H5I  +  AgOH = C2H5-OH  +  Agl. 
Ethyl  iodide.  Ethyl  alcohol. 

3.  By  the  heating  of  their  esters  (better  the  ester  acids)  with  water, 
alkaline  hydroxides,  or  acids: 

C2H5(C2H302)  +  KOH = C2H5-OH  +  K(C2H302). 
Ethyl  acetate.  Ethyl  alcohol. 

4.  By  treating  primary  amines  with  nitrous  acid: 

CjH.NHa  +  HN02=  CgH^OH  +  N^ + H^O. 

Preparation  of  Secondary  Alcohols.     1.  The  secondary  alcohols  are  ob- 
tained by  the  action  of  nascent  hydrogen  upon  the  ketones: 

CH3-CO-CH3  +  H2=  CH3-CH  (OH) -CH3. 
Acetone.  Isopropyl  alcohol. 

2.  From  the  secondary  iodides  (p.  349)  by  boihng  with  KOH; 
CH3-CHI-CH3  +  KOH=CH3-CH(OH)-CH3+KI. 

Preparation  of  Tertiary  Alcohols.     1.  The  tertiary  alcohols  are  obtained 
from  the  tertiary  iodides  (p.  349)  by  boihng  them  with  water. 

2.  From  zinc  alkyls  by  means  of  acid   chlorides    (ketones,  q.v.,  are 
formed  by  short  action) : 

Zn(CH3)2+CH3-COCl+HOH=ZnCl(OH)  +  (CH3)3  =  COH. 

4.  Fatty  Acid  Series. 

General  formula  CnHjnOs. 


Formic  acid, 

CH2O2. 

Laurie  acid, 

C-,H,,0^ 

Acetic  acid, 

C,H,03. 

Myristic  acid, 

CuH^sO,. 

Propionic  acid 

,  C3HeO,. 

Palmitic  acid. 

c„H3A. 

Butyric  acid, 

C,H«0,. 

Stearic  acid, 

C,sH3eO^ 

Valeric  acid. 

C,H.oO,. 

Arachidic  acid, 

C2oH4oOa. 

Caproic  acid, 

CeH,A. 

Lignoceric  acid 

Cj^H^gOj. 

Caprylic  acid. 

CsH.eO^. 

Cerotic  acid. 

C.eH,A. 

Capric  acid. 

CioHzoOz- 

Melissic  acid. 

CsoHeoOj. 

Properties.  The  monatomic,  monobasic  acids  of  the  monohydric 
alcohols  are  also  called  fatty  acids  because  the  higher  members  are 
found  combined  in  the  fats.  From  butyric  acid  upward  we  have 
isomeric  fatty  acids,  which  differ  from  each  other  by  having  different 
boihng-  or  melting-points.    - 

The  lower  members  at  ordinary  temperatures  are  caustic,  pungent 
liquids,  soluble  in  water  with  a  strong  acid  reaction,  while  the  inter- 


CLASSIFICATION.  345 

mediate  members  have  an  odor  similar  to  perspiration  and  are  less 
soluble  in  water.  From  C10H20O2  upward  the  acids  are  sohds, 
insoluble  in  water,  generally  without  taste  or  odor  and  can  only 
be  distilled  without  decomposition  in  a  vacuum. 

All  the  members  of  this  series  are  readily  soluble  in  alcohol  and 
ether  and  are,  with  the  exception  of  formic  acid,  acted  upon  only 
with  difficulty  by  oxidizing  agents.  Carbon  dioxide  expels  them 
from  their  compounds. 

Besides  the  replacement  of  the  hydrogen  of  the  COOH  group 
by  metals  (salt  formation),  by  alcohol  radicals  (ester  formation)  and 
acid  radicals  (anhydride  formation) ,  we  can  also  replace  the  hydroxyl 
of  the  COOH  group  by  atoms  or  groups  of  atoms,  also  the  non-replace- 
able (intraradical)  hydrogen. 

In  this  last  case  bodies  having  all  the  properties  of  the  acids  are 
obtained,  as  the  COOH  is  still  intact  (p.  335).  These  acids  are 
designated  «,  /?,  7-,  see  p.  330. 

Every  fatty  acid  can  be  reduced  to  its  aldehyde  if  a  salt  of  the 
acid  is  heated  with  a  formic  acid  salt  (a  formate) : 

CH3-C00Na+  H-COONa  =  CH3-CHO+  Na^COj. 

Sodium  Sodium  Ethyl-  Sodium 

acetate.  formate.  aldehyde.  carbonate. 

On  the  distillation  of  a  salt  of  the  fatty  acids  with  caustic  alkalies 
the  carboxyl  group  is  split  and  replaced  by  hydrogen,  yielding  hydro- 
carbons which  contain  one  C  atom  less  than  the  acid  used:  e.g., 
CH3-C00Na+  JNaOH  =  CH3  -H+  Na^COg. 

Sodium  acetate.  Methane. 

On  the  dry  distillation  of  the  calcium  salts  of  the  fatty  acids 
ketones  are  obtained: 

(CH3COO)2Ca  =  CH3-CO-CH34-CaC03. 

If  a  galvanic  current  is  passed  through  a  concentrated  solution 
of  an  alkali  salt  of  the  fatty  acids,  the  alkali  metal  is  set  free  at  the 
negative  pole,  with  a  decomposition  of  the  water  and  the  liberation 
of  hydrogen,  while  at  the  positive  pole  carbon  dioxide  and  a  satu- 
rated hydrocarbon  are  set  free: 

2CH3-COONa  =  C,U,+  200^+  2Na. 

From  this  behavior,  as  well  as  from  the  means  of  formation,  it  is 
evident  that  the  fatty  acids  contain  alkyl  as  well  as  a  carboxyl 
groups. 


346  ORGANIC  CHEMISTRY. 

Occurrence.  Certain  of  the  fatty  acids  occur  free  in  nature,  while 
a  great  number  occur  as  esters,  especially  as  waxes  and  fats  (which  see). 

Preparation.     1.  By  the  oxidation  of  primary  alcohols  and  aldehydes: 
CH3-OH  +  0^=  CH2O2  +  H,0. 

2.  By  boiling  the  alkyl  cyanides  (nitriles)  with  acids  or  alkalies  when 
the  carbon  of  the  cyanide  group  is  converted  into  the  carboxyl  group, 
while  the  nitrogen  is  split  off  as  ammonia : 

CH3-CN  +  2H-0-H  +  HCl   =CH3-C00H  +  NH4CI. 
CH,-CN+  H-0-H  +  KOH=CH3-COOK  +  NH3. 

Methyl  cyanide.  Potassium  acetate. 

3.  By  the  action  of  carbon  dioxide  upon  sodium  alkyle  ; 

CH3Na  +  C02=CH3-COONa  (sodium  acetate). 

4.  From  the  alkyl  derivatives  of  acetoacetic  ester  (which  see)  by  al- 
coholic potash. 

5.  From  the  oxy-fatty  acids  (which  see)  by  heating  with  HI: 

CH2(0H)-C00H  +  2HI = CH3-COOH  +  Hp  + 1^. 

6.  By  the  oxidation  of  secondary  and  tertiary  alcohols  and  ketones 
by  chromic  acid  we  obtain  fatty  acids  which  contam  less  carbon  than 
the  original  substance. 

5.  Methane  and  its  Derivatives. 

Methane,  Methyl  Hydride,  Marsh-gas,  Fire-damp,  CH4. 

Occurrence.  It  is  formed  in  the  slow  decomposition  of  organic 
substances  with  lack  of  air,  and  is  therefore  found  in  coal-mines,  as 
well  as  in  the  gases  which  are  evolved  from  marshy  ground  and 
stagnant  water.  In  certain  localities  it  streams  up  from  fissures  in 
the  earth  (holy  fire  of  Baku) ,  and  it  is  also  evolved  from  the  earth 
with  petroleum.  It  is  also  found  in  the  salt-mines  of  Wieliczka  and 
in  the  hot  springs  of  Aachen  and  Weilbach.  Methane  is  produced 
in  the  dry  distillation  of  many  organic  bodies  (wood  and  coal),  hence 
it  occurs  to  a  considerable  extent  in  illuminating-gas  (40-50  per  cent.). 
Methane  exists  in  the  intestinal  gases  often  in  large  quantities 
(even  to  38  per  cent.),  and  originates  chiefly  from  the  decomposition 
of  the  cellulose.  It  is  formed  when  hydrogen  acts  upon  carbon 
at  1200°,  and  in  connection  with  ethane  and  acetylene  when  the 
electric  current  passes  between  carbon  poles  in  hydrogen  gas. 

Preparation.  1.  A  mixture  of  carbon  disulphide  and  sulphuretted 
hydrogen  is  passed  over  red-hot  copper: 

CS^-f  2H2S+  8Cu  =  CH,+  4CU2S. 

2.  Ordinarily  it  is  prepared  by  heating  sodium  acetate  with  sodium 
hydroxide  :  CH3-C00Na+  NaOH  =  CH,+  Na^CO,. 


METHANE  AND  ITS  DERIVATIVES.  347 

Properties.  Colorless  and  odorless,  readily  inflammable  gas,  nearly- 
insoluble  in  water  and  liquefiable  at  -  82°  under  a  pressure  of  55  atmos- 
pheres. With  air  it  forms  an  explosive  mixture  (fire-damp  of  the 
coal-mines):  CH4+40=C02+2H20;  mixed  with  a  corresponding 
quantity  of  chlorine  we  obtain  in  diffused  daylight  chlorine  substi- 
tution products,  CH3CI,  CH2CI2,  CHCI3,  CCI4;  this  action  takes  place 
with  explosive  violence  in  the  sunlight. 

Methyl  chloride,  monochlormethane,  CH3CI  (preparation  see  page 
348),  is  a  colorless  gas  having  a  pleasant  odor  and  hquefiable  at  —25°, 
inflammable,  and  burning  with  a  beautiful  green  flame.  It  occurs  in 
commerce  liquefied  in  sealed  glass  tubes,  and  is  used  in  medicine. 

Trichlormethane,  Chloroform,  CHCI3.  Preparation.  1.  In  large 
quantities  by  distilling  ethyl  alcohol  or  acetone  with  chloride  of  lime, 
whereby  trichloraldehyde  (chloral)  is  first  formed,  which  is  further 
decomposed  into  chloroform  and  calcium  formate  by  the  action  of 
the  caustic  lime  always  present  in  the  chloride  of  lime. 

2.  So-called  chloral-chloroform,  or  English  chloroform,  is  obtained 
by  distilling  trichloraldehyde  (chloral)  with  caustic  alkah,  which 
decomposes  into  alkali  formate  and  chloroform  (see  Trichloraldehyde). 

Properties.  Colorless  liquid  having  a  sweetish  odor,  boiling  at  62°, 
and  solidifying  at  —70°.  It  is  only  slightly  soluble  in  water,  but  solu- 
ble in  ether,  alcohol,  and  fatty  oils;  it  burns  with  difficulty  and  is 
used  as  an  anaesthetic  and  as  a  solvent  for  bromine,  iodine,  alkaloids, 
phosphorus,  resins,  etc. 

By  the  action  of  air  and  light  chloroform  is  in  part  decomposed  into 
carbon  oxychloride:  CHCl,  +  0=C0Cl2  +  HCL  The  addition  of  some 
alcohol  and  keeping  it  in  the  dark  prevents  this  decomposition;  hence 
commercial  chloroform  contains  about  1  per  cent  alcohol  and  has  a 
specific  gravity  of  1.489.  On  warming  with  alcoholic  potash  it  is  decom- 
posed into  potassium  chloride  and  formate  (p.  352)  while  on  warming 
with  alcoholic  potash  and  ammonia  it  yields  potassium  cyanide:  CHCI3+ 
NH3  +  4K0H=CNK  +  3KC1  +  4H,0.  On  heating  chloroform  with  amhne 
and  alcoholic  potash  the  characteristic  odor  of  phenyl  carbylamine  is  pro- 
duced (detection  of  traces  of  chloroform;  see  Carbylamines) .  Recently 
pure  chloroform  has  been  prepared  by  cooUng  ordinary  chloroform  to 
crystallization  TPictet's  chloroform). 

Tri-iodomethane,  Iodoform,  CHI3.  Preparation.  1.  By  the  action 
at  ordinary  temperatures  of  iodine  and  caustic  alkali  upon  ethyl 
alcohol,  acetone,  and  many  other  organic  substances  containing  a 
methyl  group  (but  not  from  methyl  alcohol):  C2H5OH+ 81+ 6K0H - 
CHI3+  H-COOK+  5KI+  5H2O. 


348  ORGANIC  CHEMISTRY, 

2.  By  the  electrolysis  of  an  aqueous  KI  solution  containing  a 
little  alcohol,  whereby  1+  KOH  are  produced,  and  these  acting  upon 
the  alcohol  form  CHIg. 

Properties.  Yellow  hexagonal  crystalline  plates  which  melt  at  120°, 
have  a  persistent  odor,  are  volatile,  and  soluble  in  ether,  alcohol,  gly- 
cerine, fatty  oils,  but  not  soluble  in  water. 

Tribrommethane,  bromoform,  CHBrg,  prepared  after  the  manner  of 
iodoform,  is  a  colorless  liquid  boiling  at  148°  to  150°,  and  having  an  odor 
similar  to  chloroform  and  a  sweetish  taste. 

Tetrachlormethane,  carbon  tetrachloride,  CCI4,  is  obtained  as  the  final 
product  in  the  action  of  chlorine  upon  methane,  methyl  chloride,  chloro- 
form, and  by  the  action  of  chlorine  upon  boiling  carbon  disulphide.  It 
is  a  colorless  liquid  boiling  at  78°,  and  serves  as  a  solvent  and  an  extrac- 
tion medium  in  place  of  the  inflammable  carbon  disulphide,  ether,  etc. 

Halogen  Derivatives  of  the  Limit  Hydrocarbons  in  General. 

1.  All  the  halogens  can  be  replaced  atom  for  atom  by  nascent  hydrogen 
and  the  corresponding  hydrocarbon  is  obtained. 

2.  As  the  halogens  can  be  readily  exchanged  for  other  monovalent 
atoms  or  groups  of  atoms,  these  derivatives  serve  in  the  preparation  of 
many  other  compounds.  The  iodides  are  the  best  suited  for  this  purpose, 
the  bromides  less  so,  and  the  chlorides  still  less  so. 

3.  On  heating  with  alkali  hydroxides  (better  with  moist  silver  oxide, 
AgoO  +  HjO)  the  halogens  are  replaced  by  hydroxyl:  CH3l  +  K0H  = 
CH3-OH  +  KI. 

4.  By  the  action  of  caustic  alkalies  in  alcoholic  solution  upon  the  halo- 
gens unsaturated  hydrocarbons  are  produced: 

CH3-CH2-CH2CI  +  KOH = CH3-CH=CH2  +  KCl  +  H^O. 

Propyl  chloride.  Propylene. 

5.  On  heating  with  potassium  hydrosulphide  or  sulphide  the  halogens 
are  replaced  by  HS  or  S : 

CH3l  +  KSH=KI   +CH3SH  (methyl  mercaptan); 
2CH3I+  K2S  =2KI  +  (CH3)2S  (methyl  sulphide). 

6.  Ammonia  replaces  the  halogens  by  the  amido  group  NHj: 

CH3I  +  NH3=  CH3-NH2  +  HI. 

7.  On  heating  the  halogens  with  zinc  we  obtain  the  zinc  compounds 
of  thealkyls:   2CH3l  +  2Zn  =  Zn(CH3)2  +  Znl2. 

8.  On  heating  an  excess  of  halogen  alkyls  with  zinc  (or  sodium,  p.  341) 
we  obtain  the  higher  hyurocarboub:    2CH3l  +  Zn  =  C2H6  +  Znl2. 

9.  The  halogen  derivatives  burn  with  a  greenish  flame,  and  the  halo- 
gens can  only  be  detected  gfter  the  destruction  of  the  organic  substance 
(see  p.  310). 

10.  Preparation.  The  monoderivatives  are  prepared  by  the  action 
of  the  nascent  halogen  acids  upon  the  monohydric  alcohols  by  distilling 
the  latter  with  sodium  chloride  and  sulphuric  acid,  or  by  distilling  with 
bromine  or  iodine  and    phosphorus.      Phosphorus    trihalogenide    is  fiiot 


METHANE  AND   ITS   DERIVATIVES.  349 

formed,  which  is  decomposed  by  the  alcohols  in  the  same  manner  as 
with  water: 

PBrg + 3H0H        =  H3PO3  +  3HBr. 
PBr3 + 3CH3(OH)  =  H3PO3  +  3CH3Br. 

They  are  also  produced  by  the  action  of  the  halogens  upon  the  limit  hydro- 
carbons. If  iodine  derivatives  are  to  be  prepared  according  to  this  last 
method,  oxidizing  bodies  must  be  added  at  the  same  time  in  order  to 
destroy  the  HI  formed  (see  p.  322). 

Diderivatives  are  prepared  by  the  action  of  the  halogens  upon  the  hy- 
drocarbons, CnH-'n  (see  Olefines).  By  the  further  action  of  the  halogens 
upon  mono-  and  diderivatives  all  of  the  hydrogen  can  be  replaced  atom 
for  atom. 

Secondary  derivatives  (p.  329)  are  obtained  by  the  action  of  halogen 
acids  upon  the  secondary  alcohols,  also  upon  the  alkylenes  from  CgHe 
upward,  when  the  halogens  are  attached  to  the  carbon  atom  poorest  in 
hydrogen  and  not  to  the  terminal  carbon  atoms: 

CH3-CH=CH2  +  HI=CH3-CHI-CH3. 

On  treating  polyhydric  alcohols  with  HI  we  generally  obtain  their 
secondary  iodine  derivatives. 

,  Tertiary  derivatives  (p.  329)  are  prepared  by  the  action  of  halogen 
acids  upon  tertiary  alcohols  (see  also  Olefines). 

Nitrochloroform,  CCl3(N02),  chlorpicrin,  is  obtained  from  many  hydro- 
carbons by  the  simultaneous  action  of  chlorine  and  nitric  acid  as  a  color- 
less irritating  fluid. 

Methyl  Hydroxide,  Methyl  Alcohol,  Wood  Spirits,  Wood  Alcohol, 
Carbinol,  CHg^OH.  Occurrence.  Methyl  alcohol  exists  with  acetic 
acid  and  acetone,  etc.,  in  the  watery  distillation  products  of  wood 
(crude  wood  vinegar),  also  as  salicylic  acid  ester  in  the  Galtheria  pro- 
cumbens  (oil  of  wintergreen) .  It  is  formed  to  a  sHght  extent  in  the 
alcoholic  fermentation  of  many  fruits. 

Preparation.  The  crude  wood  vinegar  is  neutralized  with  lime 
in  order  to  neutralize  the  acetic  acid  and  the  product  distilled.  The 
crude  wood  spirit  thus  obtained  is  treated  with  calcium  chloride, 
with  which  it  forms  the  compound  CaCl2+4CH3(OH),  and  this  can  be 
heated  above  100°  without  decomposing,  while  the  volatile  impurities 
are  driven  off.  The  residue  is  treated  with  water,  when  the  compound 
decomposes  into  its  constituents,  and  distilled,  when  the  methyl  alcohol 
passes  over. 

Properties.  Colorless  fluid,  boiling  at  67°  and  having  a  peculiar 
odor.  It  is  inflammable  and  soluble  in  water  and  yields  formaldehyde 
and  then  formic  acid  on  oxidation. 

Methyl  Aldehyde,  Formaldehyde,  Methanal,  CH2O  or  H-CH=0. 
Preparation.     1.  ]\Iethyl  alcohol  vapors  and  air  are  passed  over  incan- 


350  ORGANIC  CHEMISTRY, 

descent  spirals  of  platinum  or  copper  and  the  vapors  condensed,  when 
we  obtain  a  solution  of  methyl  aldehyde  in  methyl  alcohol. 

2.  On  heating  paraformaldehyde  (see  below)  we  obtain  pure  gaseous 
formaldehyde. 

Properties.  A  colorless,  irritating  gas  which  is  strongly  antiseptic, 
condenses  at  —20°  into  a  colorless  liquid,  solidifies  at  —90°,  and  is 
soluble  m  water. 

On  heating  formaldehyde  with  dilute  caustic  alkali  it  splits  into  methyl 
alcohol  and  formic  acid:  2CH20  +  KOH=CH40  +  H-COOK,  and  on 
standing  with  ammonia  it  yields  hexamethylentetramine :  6CH20  +  4NH3= 
(CH2)6N4  +  6H20.  On  standing  with  calcium  hydrate  formaldehyde  yields 
a  mixture  of  sugars,  CgHiaOg,  (Loew's  formose),  and  with  protein  bodies 
(not  with  peptones)  it  forms  insoluble  elastic  masses,  and  with  gelatine 
insoluble  brittle  masses  called  glutol. 

Formalin,  formol,  is  a  35  per  cent,  watery  solution ;  formalithe  is  infu- 
sorial earth  impregnated  with  40  per  cent,  formaldehyde  solution;  ichtho- 
form  is  a  combination  with  ichthyol,  and  tannoform,  a  compound  with 
tannin. 

Paraformaldehyde,  Trioxymethylene,  (CH20)3,  separates  on  the 
evaporation  of  the  watery  or  alcoholic  solution  of  formaldehyde  as 
colorless  crystals  insoluble  in  water,  melting  at  154°,  and  which 
on  further  heating  decompose  into  gaseous  formaldehyde  (generation 
of  formaldehyde  for  disinfecting  purposes).  When  pressed  with 
carbon  it  forms  carboformal  cakes  which  when  ignited  generate  for- 
maldehyde and  are  used  for  disinfecting  purposes. 

The  Aldehydes  in  General.  1.  They  are  colorless,  neutral,  irritating 
bodies;  the  lower  members  are  colorlees  fluids  (formaldehyde  being  a  gas) 
having  an  irritating  odor,  soluble  in  water,  and  volatile  without  decom- 
position. As  the  C  atoms  increase  they  lose  their  odor,  solubility,  etc., 
and  the  higher  members  are  solids  which  are  odorless  and  only  volatile 
without  decomposition  in  vacuo.  They  have  a  strong  reducing  action 
because  they  are  readily  oxidized  to  the  corresponding  acid;  thus  the  alde- 
hydes decompose  an  ammoniacal  silver  solution  with  the  separation  of 
metallic  silver.  As  no  evolution  of  gas  takes  place  in  this  reduction,  the 
silver  deposits  as  a  mirror  upon  the  surface  of  the  glass;  hence  aldehydes 
produce  a  silver  mirror. 

2.  The  alkali  bisulphites  give  crystalline  insoluble  compounds  with 
the  aldehydes:  CH3CH=0  +  NaHS03=CH3CH(0H)(NaS03). 

3.  The  aldehydes  are  readily  transformed  into  polymers,  especially  in 
the  presence  of  small  quantities  of  acids  or  salts  (particularly  ZnClj)  at 
ordinary  temperatures.  At  higher  temperatures  condensation  takes  place 
(see  p.  319  and  Ethyl  Aldehyde). 

4.  Heated  with  caustic  alkalies  the  aldehydes  yield  resinous  masses 
of  high  molecular  weight  (aldehvde  resins). 

5.  On  oxidation  they  yield  the  corresponding  acid. 

6.  By  nascent  hydrogen  they  are  converted  into  their  alcohols. 


METHANE  AND  ITS  DERIVATIVES.  351 

7.  With  hydroxy lamin  the  aldehydes  give  aldoximes  (p.  331): 

CH3CH=0  +  H2N-OH  =  CH3-CH=N(OH)  +  H2O. 

8.  By  addition  with  alcohols  they  give  so-called  alcoholates: 

CH„C-H=0  +  C2H50H  =  CH3-Ch/^^?jj  ; 

while  with  alcohols  with  the  elimination  of  water  the  aldehydes  form  so- 
called  acetals: 

CH3CH=0  +  2 (C^H.OH)  =  CH3-CH (OC^H,),  +  TI^O  (ethylal) . 

With  mercaptans  (p.  332)   they  form  mercaptals,  corresponding    to  the 
acetals: 

CH3-CH=0  +  2(C2H5-SH)  =  CH3-CH(SC2Hs)2  +  H^O. 

9.  The  aldehydes  give  cyanides  of  the  next  highest  oxyacid  (see  Lactic 
Acid)  when  treated  with  hydrocyanic  acid: 

CH3CH=0  +  HCN  =  CH3-CH(OH)(CN). 

10.  With  ammonia  they  form  aldehyde  ammonias,  CH3-CH(OH)(NH2), 
which  (with  the  exception  of  that  with  formaldehyde,  p.  350)  yield  pyridin 
bases  on  heating. 

11.  With  1  molecule  of  phenylhydrazin,  CeHg-HN-NHg,  the  aldehydes 
and  ketones  unite  with  the  elimination  of  water,  generally  forming  insol- 
uble compounds,  the  hydrazons: 

CH3CH=0  +  C6H5-HN-NH2= C6H5-HN-N=CH-CH3 + B^O. 

Phenylhydrazin  therefore  serves  in  the  detection  of  the  aldehyde  and 
ketone  groups  and  in  the  synthesis  of  sugars  (see  Carbohydrates). 

12.  Preparation,  a.  With  the  exception  of  formaldehyde  they  are 
prepared  by  the  careful  oxidation  of  the  corresponding  primary  alcohols 
(p.  333). 

b.  By  distilling  the  corresponding  acids  or  their  salts  with  a  formate: 

CHgCOONa  +  HCOONa=  Na^COg  +  CH,CH=0. 

Sod.  acetate.      Sod.  formate.  Acetaldehyde. 

c.  From  the  dihalo^en  derivatives  of  the  hydrocarbons  by  boiling  with 
water :  CH3-CHCI2  +  H^O  =  CH3-CH=0  +  2HC1. 

Methylmercaptan,  CH3~SH,  occurs  to  a  slight  extent  in  human 
intestinal  gases,  as  well  as  in  the  urine  after  eating  asparagus,  and  is 
produced  in  the  dry  distillation  and  putrefaction  of  many  foodstuffs. 
It  is  a  colorless  liquid  boiling  at  60°  and  has  a  nauseating  odor. 

Methylsulphide,  (0113)28,  methylsulphur  ether,  is  a  liquid  having 
an  unpleasant  odor  and  boiling  at  116°. 

Mercaptans  and  Sulphur  Ethers  in  General  (p.  332).  1.  Both  are  col- 
orless volatile  liquids  nearly  insoluble  in  water  and  having  a  nauseating 
odor  similar  to  leeks  or  onions. 

2.  The  mercaptans  are  faintly  acid  and  readily  form  salts  with  bases 

and  metallic  oxides,  the  so-called  mercaptides,  (CH3-S)2Hg.       In  the  air 

they  oxidize  with  the  formation  of  disulphides:   2CH3-HS  +  0=  (CHP2S2  + 

H,0.     When  oxidized  by  nitric  acid  they  yield  sulphonic  acids  (which  see) : 

CH3SH + 30 = CH3-SO3H. 


352  ORGANIC  CHEMISTRY, 

3.  The  sulph-ethers  give  with  alkyl  iodides  the  sulfin  or  sulfonium 
iodides,  in  which  the  sulphur  exists  as  tetravalent  sulphur:  (CH3)2S+CH3l 
=  (0113)381.  These  bodies  give  with  moist  silver  oxide  bases  which  are 
exactly  similar  to  the  alkali  hydroxides,  the  sulp.n  or  sulfonium  bases: 
(CHO^SCOH).  On  oxidation  the  sulph-ethers  first  yield  sulfoxides, 
(CH3)2S  +  0=:(CH3)2SO,  then  SM^/ones,  (CH3)2S  +  02- (CH3)2S02. 

4.  Formation  of  mercaptals,  see  p.  351,  g,  and  of  mercaptols,  p.  371, 2- 

5.  Preparation,  see  p.  348,5. 

Formic  Acid,  CH^Oj  or  H~COOH.  Occurrence.  In  ants  and 
caterpillars,  from  which  it  can  be  obtained  by  distillation  with  water; 
in  certain  mineral  waters,  in  peat,  in  pine  needles,  in  nettles,  in  the 
bee,  and  hence  in  honey,  in  human  urine,  leucamic  blood,  in  various 
animal  secretions,  in  the  soap- tree,  and  in  the  fruits  of  the  tamarind. 

Formation.  1.  In  the  oxidation  of  methyl  alcohol,  of  sugar,  and  of 
starch  by  chromic  acid  or  by  manganese  dioxide  and  sulphuric  acid. 

2.  By  the  action  of  hydrogen  or  water  upon  COg,  or  of  hydrogen  upon 
CO  under  the  influence  of  the  dark  electric  discharge. 

3.  Formic  acid  is  also  produced  by  the  decomposition  of  chloroform, 
bromoform,  and  iodoform  by  the  aid  of  alcoholic  solution  of  caustic  potash; 

CHCI3  +  4K0H = H-COOK  +  3KC1 4-  2H2O ; 

or  from  hydrocyanic  acid  by  keeping  the  same  in  watery  solution: 

CNH  +  2H20= HCOO(NH,). 

Hydrocyanic  acid.         Ammonium  formate. 

Preparation.  1.  Formic  acid  is  prepared  in  larger  quantities  by 
heating  oxalic  acid: 

HOOC-COOH  =  H-COOH+  CO^. 

Oxalic  acid.  Formic  acid. 

This  decomposition  takes  place  best  in  the  presence  of  glycerine  at  100°- 
110°,  otherwise  the  free  oxalic  acid  in  part  sublimes  undecomposed.  If  the 
temperature  is  raised  above  110°,  then  glycerin  monoformate  is  formed, 
and  this  on  further  heating  yields  allyl  alcohol,  C3H5-OH  (which  see). 

2.  By  passing  carbon  monoxide  over  the  alkali  hydroxides  at  a 
pressure  of  several  atmospheres  or  at  200°,  NaOH+CO=H""COONa, 
and  distilling  the  formate  produced  with  dilute  mineral  acids. 

Properties.  Colorless  irritating  liquid,  causing  blisters  when 
applied  to  the  skin.  It  solidifies  at  1°  and  melts  at  9°,  while  it  boils  at 
99°.  It  mixes  with  water  and  alcohol  and  its  vapors  are  inflammable. 
Formic  aciji  has  a  reducing  action,  as  it  is  readily  oxidized  to  carbon 
dioxide,  H-COOH+0=C02+H20,  and  therefore  precipitates  silver 
as  a  black  powder  from  its  solutions,  and  white  mercurous  chloride 
from  a  solution  of  mercuric  chloride  (detection).  When  warmed 
with  concentrated  sulphuric  acid  it  decomposes  into  carbon  men- 


'     ETHANE  AND  ITS  DERIVATIVES.  353 

oxide  and  water:  CH202  =  CO+H20;   and  when  heated  to  redness 
with  caustic  alkaU  it  generates  hydrogen: 

H-COOK+  KOH  =  K2CO3+  2H. 

Officinal  formic  acid  contains  75  per  cent,  water  and  25  per  cent,  formic 
acid. 

Formic  acid  spirits,  formerly  obtained  by  distilling  ants  with  alcohol,  is 
now  prepared  by  dissolving  1  part  formic  acid  in  24  parts  dilute  alcohol. 

Formates  are  all  soluble  in  water  and  crystalline.  They  are  prepared 
by  dissolving  metallic  oxides  in  the  diluted  acid  and  evaporating  the  solu- 
tion, etc. 

Ammonium  formate,  H-C00(NH4),  is  prepared  by  neutralizing  formic 
acid  with  ammonia  and  evaporating,  when  colorless  prisms  are  obtamed. 
If  these  are  heated  to  180°,  they  decompose  into  Uquid  formamide  (p.  336) 
aid  water:  H-COO(NHJ  =  H-Cq- NH^  +  HgO,  which  boils  at  200°  and 
when  quickly  heated  decomposes  into  CO  +  NH3.  Ammonium  formate 
and  formamide  on  heating  with  phosphorus  pentoxide  yield  hydrocyanic 
acid  (HCN  =  formonitrile,  p.  384):  H-COO(NH4)  =  HCN  +  2H20.  Thus 
from  a  harmless  body  there  is  a  transition  into  a  violent  poison  by  the  split- 
ting off  of  water.  On  the  other  hand,  dilute  hydrocyanic  acid  can  readily 
take  up  water  and  be  transformed  into  ammonium  foimate(p.  352). 

6.  Ethane  and  its  Derivatives. 

Ethane,  ethyl  hydride,  CjHe  or  HgC'CHg  (p.  340),  is  obtained  on 

heating  methyl  iodide  with  zinc,  2CH3l+Zn  =  Znl24-CH3~CH3,  and 

also,  mixed  with  methane  and  acetylene,  when  the  electric  arc  plays 

between  carbon  poles  in  hydrogen  gas.     It  forms  a  colorless  gas  which 

liquefies  at  4°  and  a  pressure  of  46  atmospheres. 

Ethyl  chloride,  CgHgCl,  is  obtained  in  the  same  manner  as  methyl 
chloride,  and  is  a  colorless,  pleasant-smelling  liquid  which  produces 
insensibility,  boils  at  12°,  and  therefore  is  used  in  the  production  of 
local  anaesthesia. 

A  mixtu'-e  of  tri-,  tetra-,  and  pentachlorethane  was  formerly  used  as 
an  ana?sthetic  in  place  of  chloroform. 

Ethyl  bromide,  CgHjBr,  is  prepared  by  distilling  ethyl  alcohol  with 
sulphuric  acid  and  potassium  bromide,  when  ethyl  sulphuric  vcvl  is  first 
produced  and  then  decomposes  by  the  KBr  into  rotaPF-ium  bisulphate 
and  ethyl  bromide.  It  is  a  colorless  liquid  boiling  at  39°,  and  is  insoluble 
in  water  but  soluble  in  alcohol.  It  decomposes  when  exposed  to  air  and 
light,  and  serves  as  an  anaesthetic.  It  must  not  be  mistaken  for  the 
poisonous  ethylendibromide,  C2H4Br2. 

Ethyl  Hydroxide,  Ethyl  alcohol,  Alcohol,  Spirits  of  Wine,  Etha- 
nol,  CaH^OH.  Occurrence.  In  small  quantities  free,  or  as  esters  in 
certain  plants,  and  also  in  animal  organs ;  with  acetone  in  the  urine 
of  many  diabetics.  It  is  formed  to  a  slight  extent  in  the  dry  dis- 
tillation of  many  organic  substances;  hence  it  is  found  in  coal-tar 
and  bone-oil,  etc. 


354  ORGANIC  CHEMISTRY. 

Pormation.  1.  From  aldehyde  by  reduction  (p.  350).  2.  From 
ethyl  chloride  by  means  of  alkali  hydroxide  (p.  348).  3.  Direct  from  C 
and  H  as  follows:  If  the  electric  spark  is  passed  between  carbon  poles 
surroimded  by  hydrogen,  acetylene,  02^2*  is  produced,  which  with  nascent 
hydrogen  forms  ethylene,  CgH^.  This  unites  with  sulphuric  acid,  forming 
ethylsulphuric  acid,  C2H5HSO4,  which  when  distilled  with  caustic  alkalies 
yields  alcohol: 

CaH^HSO,  +  2K0H = CaH.-OH  +  K2SO4  +  H^O. 

Preparation.  On  a  large  scale  alcohol  is  prepared  by  fer- 
mentation (p.  325)  of  various  kinds  of  sugars,  for  instance  grape- 
sugar,  invert-sugar,  maltose,  which  is  brought  about  by  yeast  or 
so-called  Saccharomyces.  The  sugars  decompose  into  alcohol  and 
carbon  dioxide: 

CeH,,Oe  =  2C2HeO  +   2C0,. 

Grape-sugar.       Alcohol.      Carbon  dioxide. 

In  the  manufacture  of  alcohol  the  purer  forms  of  sugar  are  not 
used,  but  rather  molasses  or  bodies  rich  in  starch,  such  as  potatoes, 
where  the  starch  is  first  converted  into  fermentable  maltose  by  the 
action  of  diastase  (see  Ferments). 

The  fermented  Hquid  is  distilled,  when  the  alcohol,  which  boils 
at  79°,  passes  over  with  some  water,  while  the  non-volatile  bodies 
and  the  greater  part  of  the  water  remain  (which  when  obtained  from 
potatoes  is  a  valuable  food  for  cattle  on  account  of  the  proteids  it 
contains). 

If  the  alcohol  containing  water  is  distilled  several  times  (or  only 
once  in  specially  constructed,  so-called  column  apparatus)  and  the 
first  portion  collected,  then  we  obtain  an  alcohol  which  contains  only 
8-10  per  cent,  water  and  is  sold  in  commerce  as  spirits.  The  water 
cannot  be  entirely  removed  by  further  distillation,  hence  we  are 
obliged  to  treat  the  alcohol  with  substances  which  have  a  greater 
attraction  for  water  than  alcohol  (for  this  purpose  we  allow  the 
spirits  to  stand  over  CaO  or  CaClg  for  24  hours)  and  then  distilling. 
The  product  is  anhydrous  alcohol  or  absolute  alcohol. 

In  alcoholic  fermentation  small  quantities  of  glycerine,  succinic  acid, 
as  well  as  mixtures  of  propyl,  isobutyl,  amyl  alcohols,  and  esters  of  fatty 
acids,  are  always  formed  besides  the  ethyl  alcohol.  This  mixture  is  callecl 
fusel-oil;  it  has  a  higher  boiling-point  than  the  alcohol,  and  hence  distils 
over  only  to  a  slight  extent  with  the  alcohol.  These  products  give  the 
peculiar  odor  and  taste  to  the  crude  forms  of  spirits,  but  they  can  be 
removed  by  passing  the  vapors  of  the  crude  spirits  over  charcoal.  The 
fusel-oil   is   separated   by   distillation   from   the   liquid   which   remains 


ETHANE  AND  ITS  DERIVATIVES.  355 

(phlegma)  after  the  repeated  distillation  of  the  crude  spirits   (rectifica- 
tion). 

Properties.     Colorless,  nearly  odorless  liquid  having  a  burning 

taste;  it  boils  at  78.5°,  has  a  specific  gravity  of  0.79  at  15°  C,  and 

sohdifies  at   —131°,  forming  a    white  crystalhne   mass.      It  burns 

with  a   bluish   hardly   perceptible   flame.     Alcohol   attracts   water 

with  avidity  and  mixes  therewith  in  all  proportions,  whereby  heat  is 

evolved  and  a  diminution  in  volume  occurs.    It  dissolves  resins,  fats, 

volatile  oils,  bromine,  iodine,  etc.,  also  many  salts  and   gases.     By 

oxidizing  agents  or  by  certain  ferments  it  is  converted  into  aldehyde 

and  acetic  acid,  and  with  sodium  it  forms  crystalline  sodium  ethylate, 

C^Hj-ONa  (p.  343). 

The  amount  of  alcohol  in  watery  liquids  is  determined  from  the  spe- 
cific gravity  with  proper  regard  for  the  temperature.  As  a  contraction 
takes  place  on  mixing  alcohol  and  water,  the  specific  gravity  of  such  mix- 
tures has  been  determined  and  tables  are  given  which  give  the  composi- 
tion of  such  mixtures.  If  the  liquid  contains  other  bodies  in  solution,  the 
alcohol  must  first  be  distilled  off  and  the  amount  of  alcohol  determined 
from  the  specific  gravity  of  the  distillate.  Small  amounts  of  alcohol  can 
be  detected  by  converting  it  into  iodoform,  which  is  recognized  by  its 
odor  and  crystalline  form. 

Solid  alcohol  is  obtained  by  dissolving  8  to  10  per  cent,  sodium  soap 
or  stearic  acid  in  commercial  alcohol. 

Methylated  spirit,  which  is  used  for  technical  purposes,  contains  3  vol. 
per  cent,  of  a  mixture  of  methyl  alcohol  and  pyridin  bases. 

Rectified  spirit  is  an  alcohol  containing  9  to  10  vol.  per  cent,  water 
and  has  a  specific  gravity  of  0.830  to  0.834. 

The  word  spirits  is  also  used  to  denote  the  colorless  alcoholic  solutions 
of  many  medicinal  substances,  such  as  spirits  of  camphor,  juniper, 
lavender,  peppermint,  etc. 

Tinctures  are  alcoholic  extracts  of  plants  having  medicinal  properties; 
still  the  word  is  used  for  certain  alcoholic  and  alcohol-ether  solutions  of 
salts,  etc.,  used  in  medicine. 

Liqueurs  and  cordials  consist  of  dilute  alcohol  and  sugar  flavored 
with  ethereal  oils,  tinctures,  etc.,  and  generally  colored. 

Alcohol  containing  50  to  65  per  cent,  water  and  having  a  different 
taste  depending  upon  admixture  with  fusel-oil,  etc.,  derived  from  the 
materials  used  in  the  fermentation,  forms  certain  beverages.  We  differ- 
entiate between 

Whiskey,  which  obtained  from  crude  starchy  products,  such  as  fer- 
mented malted  grains  (corn,  rye,  barley,  oats),  from  potatoes,  and  from 
rice  (arrac). 

When  obtained  from  fermented  molasses  it  is  called  rum,  from  the 
cherry- kernel,  kirchwasser,  from  the  plum-kernel,  plum-brandy  or  Sli- 
bowitz,  from  malted  barley  and  rye  meal  with  hops  and  rectified  from 
juniper-berries  it  is  called  gin. 

Brandy  from  alcoholic  liquids.  True  brandy  is  obtained  on  the  dis- 
tillation of  wine.    The  better  kinds  are  called  cognac. 


366  ORGANIC  CHEMISTRY. 

Wine  is  an  alcoholic  liquid,  completely  fermented,  which  is  obtained 
by  the  spontaneous  fermentation  of  grape-juice  (p.  325),  without  the 
addition  of  yeast  and  without  distillation.  Wines  contain  8-10  to 
20  per  cent,  (southern  wines)  alcohol,  besides  the  constituents  of  the 
grape-juice.  Malt  wines  are  produced  by  the  fermentation  of  a  barley 
wort  (see  below)  with  a  southern  wine-yeast. 

Beer  is  an  alcoholic  (3-4  per  cent.)  liquid  still  undergoing  fermenta- 
tion and  prepared  from  starchy  bodies  (generally  barley)  without  distilla- 
tion.    The  chief  operations  are  the  following: 

Malting  consists  in  the  i>reparation  of  diastase  (see  Ferments)  by  means 
of  the  artificial  germination  of  barley  grains  and  the  interruption  of  this 
germination  by  heating  the  malt. 

The  mash  consists  in  extracting  the  malt  with  water,  when  the  diastase 
converts  the  starch  into  soluble  sugar  (maltose)  and  dextrin. 

HoTps  and  boiling.  The  solution  {wort)  obtained  in  the  mash  is  treated 
with  hops  and  boiled,  when  it  becomes  concentrated  and  the  proteids 
coagulate  and  are  precipitated  by  the  tannic  acid  contained  in  the  hops. 
The  wort  becomes  clear  and  the  constituents  of  the  hops  give  the  beer 
an  agreeable  taste  and  aids  in  preserving  the  same. 

The  fermentation  is  introduced  by  adding  yeast  to  the  wort.  After 
completion  of  the  chief  fermentation  the  "new  beer"  is  separated  from 
the  yeast  and  allowed  to  undergo  "after-fermentation."  Upon  completion 
of  the  fermentation  the  beer  is  put  in  kegs,  where  a  further  decomposition 
of  the  sugars  takes  place,  although  the  5^east-fungus  is  present  only  to  a 
slight  extent.  The  bungs  are  inserted  loosely,  and  not  driven  home  until 
a  fortnight  before  delivery,  so  that  the  carbon  dioxide  is  in  part  ab- 
sorbed and  produces  the  foam. 

Ethyl  nitrite,  CjHs'O'N^O,  is  obtained  pure  by  distilling  nitrous 
acid  (KNO2+H2SO4)  with  alcohol.  It  is  a  colorless  liquid  boiling  at 
18°  and  with  an  odor  similar  to  apples.  If  alcohol  is  distilled  with  nitric 
acid,  apart  of  the  acid  is  reduced  to  nitrous  acid  by  the  alcohol;  at  the 
same  time  aldehyde  is  formed  and  the  nitrous  acid  then  acts  upon  the 
undecomposed  alcohol,  producing  ethyl  nitrite: 

C2HeO+  HNO3  =  CH3-CHO+  H2O-}-  HNO2; 
C2H6O+  HNO2  =  C2HrO-N=0+  H2O. 

The  distillate  thus  obtained,  a  solution  of  ethyl  nitrite  in  alcohol, 
is  called  sweet  spirits  of  nitre. 

Nitroethane,  C2H5-NO2,  isomeric  with  ethyl  nitrite,  contains,  like  all 
nitro  bodies,  the  alkyl  directly  united  to  the  nitrogen.  Nascent  hydrogen 
converts  it  into  ethylamine,  while  it  changes  ethyl  nitrite  into  ethyl  alcohol 
(p.  318).  The  nitro  compounds  are  obtained  by  treating  the  alkyl  iodides 
with  silver  nitrate. 

Ethyl  nitrate,  C2H5-NO3.  Nitric  acid  has  an  oxidizing  action  upon 
alcohol,  depending  upon  the  quantity  of  nitrous  acid  it  contains  (see  Ethyl 
Nitrite).  If  the  distillation  takes  place  in  the  presence  of  urea,  then  the 
nitrous  acid  is  destroyed,  CO(NH2)2  +  2HN02=3H20  +  C02  +  4N,  and  we 


ETHANE  AND  ITS  DERIVATIVES.  357 

obtain  pure  ethyl  nitrate  as  a  colorless  liquid  boiling  at  86°,  with  a  pleas- 
ant odor,  differing  from  ethyl  nitrite. 

Ethyl  sulphate,  sulphuric  acid  ethyl  ester  (€2115)2804  (see  below) 
is  obtained  by  passing  sulphuric  anhydride  vapors  into  ethyl  ether. 
It  is  a  colorless  aromatic-smelUng  liquid  boiling  at  220°: 

(C2H5)20+S03  =  (C2H5)2SO,. 

The  Neutral  Esters  in  General.  1.  They  are  mostly  liquids  having  a  low 
boiling-point,  often  of  a  pleasant  odor,  neutral,  volatile  without  decompo- 
eition,  and  insoluble  or  nearly  so  in  water.  The  esters  of  the  lower  fatty 
acids  have  odors  hke  fruits  and  serve  as  artificial  fruit  flavors.  Nearly  all 
fruit  odors  can  be  obtained  by  admixture  of  these  various  esters.  The 
esters  of  the  acids  rich  in  C,  and  also  those  of  the  aromatic  acids,  are  mostly 
crystalline. 

2.  They  are  decomposed,  like  the  analogous  inorganic  salts,  by  boiling 
with  alkali  hydroxides.  The  alkali  metal  combines  with  the  acid,  and  the 
alcohol  radical  with  the  OH  is  set  free  as  alcohol.  This  process  is  called 
saponification  (see  Glycerin): 

FeSO,  +  2K0H = Fe(0H)2  +  K^SO,. 
aH5(CH3COO)  +K0H=C2H,0H  +  K(CH3C00). 

Ethyl  acetate.  Alcohol.      Potassium  acetate. 

They  are  also  decomposed  by  superheated  steam  or  boiling  with  acids  into 
alcohol  and  acid  with  the  taking  up  of  water.  This  process  is  called 
hydrolysis. 

3.  Heated  with  anmionia  the  esters  yield  acid  amides  and  alcohols : 

CH3-COO-C2H5  +  NH3 
Ethyl  acetate.  Acetamide. 

With  hydrazin  they  yield  hydrazids  (p.  331),  and  with  hydroxylamin  the 
hydroximic  acids  (p.  331). 

4.  Preparation,  a.  If  alcohols  are  treated  with  acids,  ester  formation 
takes  place:  CH3COOH  +  C2H,OH=CH3-COO-C2H5  +  H20.  The  water 
formed  takes  part  in  the -reaction  and  causes  a  corresponding  equilibrium 
(see  Ethyl  Sulphuric  Acid).  If  the  acids  or  their  salts  are  distilled  with  the 
alcohol  in  the  presence  of  sulphuric  acid,  or  if  HCl  vapors  are  passed 
through  the  mixture  during  the  distillation,  then  the  water  combines  with 
the  acid  and  the  reaction  is  complete. 

6.  By  the  action  of  halogen  alkyls  upon  the  silver  salt  of  the  acid  in 
question: 

3C2H5Cl  +  Ag3PO,=  (C2H,),PO,  +  3AgCl. 

c.  In  regard  to  the  preparation  of  the  esters  of  the  halogen  acids  see 
p.  353. 

Ethyl  sulphuric  acid,  (C2H5)HS04,  is  obtained  by  mixing  ethyl  al- 
cohol with  sulphuric  acid.  The  mixture  always  contains  free  sulphuric 
acid  and  unchanged  alcohol  even  when  equal  molecular  weights  of 
the  substances  are  used,  as  well  as  when  an  excess  of  sulphuric  acid 


358  ORGANIC  CHEMISTRY, 

or  alcohol  is  used,  as  a  certain  state  of  equilibrium  always  exists 
pp.  61,  62):  C^HrOH+H^SO^^C^Hj-HSO^+HOH. 

In  order  to  obtain  pure  ethyl  sulphuric  acid  from  this  mixture 
it  is  neutraUzed  by  barium  carbonate,  which  forms  insoluble  barium 
sulphate  with  the  excess  of  sulphuric  acid,  while  the  barium  ethyl 
sulphate  remains  in  solution.  This  solution  is  decomposed  by  the 
necessary  amount  of  sulphuric  acid,  the  barium  sulphate  filtered  off, 
and  the  filtrate  evaporated  in  a  vacuum  over  sulphuric  acid.  The 
pure  ethyl  sulphuric  acid  thus  obtained  is  a  colorless  oily  fluid  which 
is  readily  decomposable.  Heated  with  water  it  decomposes  into 
sulphuric  acid  and  alcohol:  (C2H5)HS04+H20  =  C2H50H+H2S04; 
while  when  heated  alone  it  yields  ethyl  sulphate  and  sulphuric  acid: 
2(C,H5)HSO,  =  (C2H5)2SO,+  H,0. 

The  Acid  Esters  or  Ester  Acids  in  General.  1.  They  are  acid-reacting, 
odorless  liquids  readily  soluble  in  water,  not  volatile  without  decomposi- 
tion (see  above),  of  acid  character,  forming  esters  and  salts.  In  general 
they  behave  like  the  neutral  esters  (which  see). 

2.  Preparation.     In  a  manner  similar  to  that  of  ethyl  sulphuric  acid. 

Ethyl  oxide,  ethyl  ether,  ether,  C2H5~0~C2H5,  incorrectly  called 
sulphuric  ether. 

Formation.     From  ethyl  iodide  and  sodium  ethylate : 

C2HrONa+  CjHsI  =  C2H5-O-C2H5+  Nal. 

Preparation.  On  a  large  scale  by  heating  1  part  alcohol  and  2 
parts  sulphuric  acid  to  140°  (with  more  sulphuric  acid  ethylene,  C2H4, 
is  obtained),  whereby  two  reactions  take  place,  the  first  being  the 
formation  of  ethyl  sulphuric  acid  and  water: 

C2H5-OH+  H2SO4  =  (C2H5)HS04+  H2O. 

The  ethyl  sulphuric  acid  at  140°  in  the  presence  of  more  alcohol 
(see  Ethyl  Sulphuric  Acid)  decomposes  into  ether  and  free  sulphuric 
acid : 

(C2H5)HS04+  C2H5-0H = c,iiro-c,-a,+ h^so^. 

The  water  formed  and  the  ether  are  distilled  off,  leaving  the  sul- 
phuric acid  behind,  and  if  more  alcohol  is  allowed  to  flow  into  the  vessel 
the  reaction  proceeds  without  interruption.  In  this  manner  a  small 
quantity  of  sulphuric  acid  transforms  a  large  quantity  of  alcohol  into 
ether,  and  this  is  the  reason  why  the  action  of  the  sulphuric  acid  was 
formerly  considered  only  as  a  contact  substance  (p.  9). 


ETHANE  AND  ITS  DERIVATIVES.  359 

Properties.  Colorless,  peculiar  pleasant-smelling  liquid  with 
burning  taste  and  having  a  specific  gravity  of  0.72.  It  boils  at  35° 
and  solidifies  at  —129°;  it  inflames  readily  and  burns  with  a  luminous 
flame.  Ether  readily  dissolves  fats,  resins,  ethereal  oils,  sulphur, 
phosphorus,  bromine,  iodine,  etc.,  and  is  sHghtly  soluble  in  water, 
but  soluble  in  all  proportions  in  alcohol.  Ether  vapor  is  very 
inflammable  and  with  air  forms  an  explosive  mixture.  Inhaled  it 
causes  stupor  and  then  complete  unconsciousness,  and  hence  is 
used  in  place  of  chloroform  as  an  anaesthetic.  On  account  of  its  vola- 
tility it  has  a  strong  cooling  action,  and  therefore  the  vaporization 
of  ether  is  used  in  the  production  of  low  temperatures,  also  as  a  local 
anaesthetic. 

Anaesthesia  ether  is  chemically  pure  ethyl  ether.  Spiritis  aetheris, 
Hoffmann's  anodyne,  is  a  mixture  of  1  part  ether  with  3  parts 
alcohol. 

Ethers  in  General.  1.  They  are  neutral,  very  stable  bodies  which  do 
not,  like  the  alcohols,  unite  with  acids  and  are  not  oxidized  by  the  halo- 
gens, but  are  substituted.  Methyl  ether  is  a  gas,  while  the  next  members 
are  volatile  liquids  having  a  characteristic  ''ethereal"  odor,  and  the 
higher  members  of  the  series  rich  in  carbon  are  solids.  They  are  oxidized 
by  nitric  acid,  etc. 

2.  All  the  hydrogen  atoms  of  ethers  show  a  similar  behavior,  and 
metallic  sodium  does  not  act  upon  them  (p.  343). 

3.  On  heating  with  water  (in  the  presence  of  some  sulphuric  acid)  in 
sealed  tubes  they  are  converted  into  thy  alcohols  with  the  taking  up  of 
water. 

4.  Preparation,  a.  The  simple  ethers  are  obtained  by  heating  the 
respective  alcohol  with  sulphuric  acid,  or  by  the  action  of  halogen  alkyls 
upon  the  sodium  alcoholates  (p.  358). 

b.  The  mixed  ethers  (those  with  two  different  alkyls)  are  obtained  by 
the  action  of  the  potassium  compound  of  an  alcohol  upon  the  iodide  of 
another  a Ikyl: 

CH3-OK     +     C.H-I     =     CHrO-C^H,     +     KI; 

Potassium  methylate.     Ethyl  iodide.      Methyl-ethyl  ether. 
or  by  heating  two  different  monovalent  alcohols  with  sulphuric  acid: 
(CH3)HS0,  +  C,H,OH = CH3-0-C,H,  +  H,SO,. 
Ethyl  peroxide,  an -O-O-CHs,  is  obtained   bv  the  action  of  ethyl 
sulphate  upon  alkaline  HA  solution.     It  is  a  liquid  havmg  a  famt  ethereal 
odor  and  boiling  at  65°. 

Ethyl  Aldehyde,  Acetaldehyde,  Ethyliden  Oxide,  Ethanal,  C2H4O 
or  CHj-CH^O.  Preparation.  1.  By  the  gentle  oxidation  of  alcohol 
by  means  of  manganese  dioxide  or  potassium  bichromate  and  sul- 
phuric acid,  when  the  aldehyde  may  be  distilled  off. 


360  ORGANIC  CHEMISTRY. 

2.  By  the  distillation  of  an  acetate  with  a  formate  (p.  351,12): 

CH3-C00Na+  H-COONa  =  CH,-  -CH=0+  2Na2C03. 

Sod.  acetate.        Sod.  formate.         Aldehyde.      Sod.  carbonate. 

3.  On  a  large  scale  in  the  purification  of  crude  alcohol  by  means  of 
charcoal  a  part  of  the  alcohol  is  oxidized  by  the  air  condensed 
in  the  pores  of  the  charcoal.  This  part  first  passes  over  in  the  dis- 
tillation, and  the  pure  aldehyde  is  obtained  from  this  portion  by  frac- 
tional distillation. 

Properties.  Colorless  irritating  liquid  having  a  pecuHar  odor, 
and  boiUng  at  21°,  and  oxidizing  in  the  air  into  acetic  acid. 

Paraldehyde,  (021^40)3.  Traces  of  mineral  acids,  phosgene  gas,  zinc 
chloride,  etc.  (p.  350,3),  at  ordinary  temperature  transform  ethyl  aldehyde 
into  its  polymer  paraldehyde  with  the  development  of  heat.  Paraldehyde 
is  a  colorless  liquid  boiling  at  124°  without  decomposition,  soluble  in 
alcohol,  ether,  and  in  9  parts  water,  and  can  be  made  crystalline  by 
strongly  cooling. 

^  Metaldehyde,  (C2H40)6,  is  produced  by  the  action  of  traces  of  mineral 
acids  upon  aldehyde  below  0°.  It  forms  white  crystals  which  sublime 
on  heating  with  a  partial  formation  of  aldehyde. 

Both  modifications  do  not  show  the  properties  of  the  simple  aldehydes 
(p.  350).  They  are  retransformed  into  ordinary  aldehyde  by  distilling 
them  with  dilute  sulphuric  acid.  If  aldehydes  are  treated  at  high  tem- 
peratures with  traces  of  mineral  acids,  etc.,  condensation  takes  place  with 
the  elimination  of  water  (p.  319) : 

2CH3CHO  =  H20  +  CH3-CH=CH-CHO  (crotonic  aldehyde). 

Aldol,  C^HsOg,  is  produced  when  aldehyde  is  allowed  to  stand  several 
days  in  contact  with  dilute  hydrochloric  acid  at  15°  C: 

CH3-CHO  +  CH3-CHO=CH3-CH(OH)-CH2-CHO. 

In  this  so-called  aldol  condensation  one  H  atom  of  one  molecule  passes 
over  into  the  other  molecule.  ^    ' 

Aldol  is  a  thick  odorless  liquid  which  readily  undergoes  polymeriza- 
tion and  which  is  converted  with  the  elimination  of  water  into  crotonic 
aldehyde,  04HpO  (see  above),  on  heating,  Aldol  is  an  aldehyde  alcohol 
which  is  derived  theoretically  from  the  corresponding  dihydric  alcohol 
and  is  also  called  ^-oxybutyl  aldehyde. 

Trichloraldehyde,  Chloral,  C2HCI3O  or  CCI3-CHO.  Preparation. 
By  passing  chlorine  into  ethyl  alcohol  and  distilling  the  crystalline 
chloral  alcoholate,  CCla'CH (OH) (O -Calls),  thus  obtained  with  sul- 
phuric acid. 

If  chlorine  is  allowed  to  act  upon  ethyl  aldehyde,  no  substitution 
of  the  intraradical  hydrogen  takes  place,  but  acetyl  chloride,  CH3~C0C1, 
is  obtained.     If  chlorine  acts  upon  alcohol,  crystalline  chloral  alco- 


ETHANE  AND  ITS  DERIVATIVES.  361 

holate  (see  p.  351,8)  is  obtained,  and  from  this  the  chloral  is  set  free 
by  sulphuric  acid : 

CCl3-CH(0H)  (0  •  C2H5)  +  H,SO,  =  CCI3-CHO+  (C2H5)HSO,+  Rfi. 

Properties.  Thick  liquid  with  peculiar  odor,  boiling  at  98°,  and 
which  gives  all  the  reactions  of  the  aldehydes.  It  is  oxidized  into 
trichloracetic  acid,  CCI3COOH,  by  means  of  nitric  acid,  and  by  caustic 
alkahes  it  is  decomposed  into  chloroform  and  a  formate  (p.  347) : 

CCI3-CHO+  KOH  =  CHCI3+  HCOOK. 

This  process  takes  place  in  the  preparation  of  chloroform,  in  that  the 
chlorine  of  the  chloride  of  lime  forms  chloral  with  the  alcohol,  and  the 
calcium  hydroxide  which  is  always  present  in  the  chloride  of  hme  decom- 
poses this  chloral  into  chloroform  and  calcium  formate: 

2CCI3-CHO  +  Ca(0H)2=  2CHCI3 + g^QQ 

When  chloral  is  treated  with  a  Httle  water  it  solidifies  to  colorless 
crystals  of  chloral  hydrate,  CCl3""CH(OH)2,  which  melt  at  58°  and  are 
readily  soluble  in  water  with  a  bitter  taste.  This  is  the  form  in  which 
chloral  is  used  in  medicine.  Chloral  hydrate  is  an  excellent  solvent 
for  many  bodies,  such  as  resins,  starch,  etc. 

Chloral  formamide,  CC13-CH<^^q/j^jj  y  is  obtained  by  bringing  chloral, 

CXI5I3-CHO,  and  formamide,  H-CO-NH2,  together.  It  forms  colorless, 
odorless,  but  bitter  crystals  which  are  soluble  in  20  parts  water  and  which 
melt  at  114°. 

Acetic  Acid,  C2H4O2  or  CH3~C00H.  Occurrence.  Acetates  are 
found  in  the  animal  kingdom,  and  free  acetic  acid  is  found  in  the  feces, 
urine,  perspiration,  and  several  parenchymatous  gland  extracts. 
Pathologically  it  is  found  in  leucaemic  blood  and  gastric  juice.  It 
occurs  free  or  as  calcium  or  potassium  acetate  in  the  juice  of  many 
plants.  Triacetin,  03115(0211302)3,  occurs  in  the  oil  of  the  Evonymus 
europseus  and  Croton  Tighum;  octyl  acetate,  (08Hi7)02H3O2,  in  the 
seeds  of  Heracleum  giganteum  and  Heracleum  sphondylium.  Besides 
other  products  it  is  found  in  the  putrefaction,  fermentation,  and  dry 
distillation  of  many  organic  bodies. 

Preparation.  1.  From  alcohol.  If  8  to  15  per  cent,  alcohol  is 
allowed  to  slowly  trickle  over  wood  shavings  previously  moistened 
with  vinegar  and  pressed  into  barrels  with  false  bottoms,  the  alcohol 
is  finely  divided  and  spread  over  a  greater  surface,  when  oxidation 


362  ORGANIC  CHEMISTRY. 

takes  place  rapidly  by  the  action  of  the  air  (under  the  influence  of 
the  vinegar  fungus).  In  order  that  the  oxidation  is  complete  the 
liquid  is  passed  through  several  times. 

Instead  of  alcohol  we  make  use  of  wine,  beer,  fermented  grain- 
mash,  fruit-juices.  The  liquid  thus  obtained  is  called  vinegar  (wine-, 
malt-,  or  fruit-vinegar)  and  contains  5-8  per  cent,  acetic  acid.  It 
also  contains  other  organic  bodies  which  give  a  yellowish-brown  or 
red  color  to  the  liquid. 

Pure  alcohol  is  not  oxidized  in  the  air  either  alone  or  when  diluted  with 
water;  nevertheless  all  oxidizing  agents,  and  also  air  or  oxygen  in  the 
presence  of  platinum-black  (p.  292),  converts  the  alcohol  first  into  alde- 
hyde and  then  into  acetic  acid.  Fermented  alcoholic  liquors  on  the  con- 
trary, when  exposed  to  the  air  soon  become  sour  of  themselves,  if  they 
do  not  contain  too  much  alcohol.  This  is  dependent  upon  the  fact  that 
these  liquids  contain  certain  salts  and  nitrogenous  compounds  which  are 
necessary  for  the  further  development  in  the  liquid  of  the  spores  of  the 
acetic  acid  fungus,  bacterium  aceti,  which  are  always  found  in  the  air 
and  which  take  the  part  of  oxygen-carriers  (analogous  to  platinum-black). 
In  the  manufacture  of  vinegar  the  wood  shavings  serve  as  nutrition  for 
the  fungus. 

2.  From  wood.  The  watery  product  obtained  on  the  dry  distilla- 
tion of  wood  and  which  contains  5-6  per  cent,  acetic  acid,  also  methyl 
alcohol,  acetone,  and  tar-oil,  is  a  brown  liquid  and  is  sold  as  crude 
wood  vinegar,  pyroligneous  acid  (crude),  and  when  purified  by  distil- 
lation occurs  in  commerce  as  a  yellow  liquid,  called  purified  wood 
vinegar  or  rectified  pyrohgneous  acid. 

3.  Anhydrous  acetic  acid  is  obtained  by  saturating  the  above- 
mentioned  varieties  of  vinegar  with  sodium  carbonate,  evaporating 
and  heating  the  residue  to  250°.  By  this  means  the  organic  con- 
taminations are  destroyed,  while  the  sodium  acetate  remains  un- 
changed and  anhydrous.  The  acetic  acid  is  obtained  from  this 
purified  sodium  acetate  by  distillation  with  sulphuric  acid: 

2CH3-COONa+  H^SO^  =  2CH3-COOH  -f  NaSO,. 

Properties.  Pure  acetic  acid,  glacial  acetic  acid,  forms  a  colorless 
crystalline  mass  which  melts  at  17°  to  a  colorless  corrosive  liquid 
having  a  specific  gravity  of  1.05,  producing  blisters  on  the  skin,  and 
boiUng  at  118°.  It  dissolves  many  organic  substances,  also  sulphur 
and  phosphorus. 

Commercial  acetic  acid  contains  30  per  cent.,  vinegar  essence,  70  per 
cent,  acetic  acid. 


ETHANE  AND  ITS  DERIVATIVES.  363 

As  acetic  acid  with  4  per  cent,  water  has  the  same  specific  gravity  as 
that  with  30  per  cent,  water,  it  is  impossible  to  determine  the  amount  of 
acetic  acid  in  watery  solutions  by  means  of  the  specific  gravity,  and  this 
can  only  be  done  by  chemical  means. 

Acetates  are,  with  the  exception  of  the  silver  and  mercurous 
salts  and  certain  basic  salts,  readily  soluble  in  water.  On  heating, 
all  acetates  are  decomposed  and  leave  a  residue;  the  alkali  ace- 
tates leaving  carbonate,  and  the  other  acetates  metallic  oxides  or 
metals. 

Detection.  On  heating  an  acetate  with  sulphuric  acid  the  charac- 
teristic odor  of  acetic  acid  is  developed;  if  alcohol  is  added  to  this 
mixture,  ethyl  acetate  is  produced,  which  is  detected  by  its  odor. 
On  heating  dry  alkaU  acetates  with  AsjOj  the  disagreeable-smelling 
alkarsine  (see  Arsines)  is  obtained. 

Potassium  acetate,  C2H3KO2,  is  obtained  by  dissolving  potassium 
hydroxide  or  potassium  carbonate  in  acetic  acid  and  evaporating  to 
dryness.  It  is  a  white  crystalline  powder  which  absorbs  moisture  from 
the  air. 

Sodium  acetate,  CjHgNaOg  +  SHjO,  forms  colorless  efflorescent  crystals 
which  are  soluble  in  1  part  water. 

Ammonium  acetate,  C2H3(NH4)02,  decomposes  on  heating  into  water 
and  acetamide:    CHg-COONH.^CH.-CO-NHa  +  HaO. 

Basic  aluminium  acetate,  H0-A1=  (0211302)2,  is  only  known  in  solution. 
An  8  per  cent,  watery  solution  having  a  specific  gravity  of  1.048  is  used 
as  a  local  astringent. 

Lead  acetate,  Pb(C2H302)2+3H20,  is  obtained  by  dissolving  lead 
oxide  in  acetic  acid  and  evaporating.  It  forms  colorless  prisms  which 
are  soluble  in  2.3  parts  water  and  which  have  a  sweetish  taste;  hence  it 
is  also  called  sugar  of  lead. 

Basic  Lead  Acetate,  Lead  Subacetate,  Pb(C2H302)2+a:PbO.  Solu- 
tions of  lead  acetate  readily  dissolve  lead  oxide  with  the  formation 
of  basic  salts  which  may  be  precipitated  by  alcohol  as  white 
crystaUine  powders  having  the  following  structure: 

CHj-COO-Pb-O-Pb-O-Pb-OOC-CH,; 
CHj-COO-Pb-O-Pb-OOC-CHj. 

Such  a  solution  of  lead  oxide  in  lead  acetate  solution  is  called 
vinegar  of  lead.  This  solution  quickly  absorb  carbon  dioxide, 
and  hence  they  become  cloudy  in  the  air  as  well  as  on  the  addition 
of   ordinary  water,  by   the  precipitation   of  basic   lead    carbonate 


364  ORGANIC  CHEMISTRY, 

(Goulard's  solution).  A  mixture  of  1  part  basic  lead  acetate  with  49 
parts  distilled  water  forms  what  is  called  lead-water,  which  only  be- 
comes slightly  cloudy  when  exposed  to  the  air. 

Cupric  acetate,  Cu(C2H302)2+H20,  obtained  by  dissolving  verdi- 
gris (p.  237)  or  copper  oxide  in  acetic  acid  and  evaporating  the  solution, 
is  a  dark-green  crystalline  body  and  soluble  in  water. 

Basic  cupric  acetate,  Cu(C2H302)2+a:CuO,  which  has  a  com- 
position analogous  to  that  of  the  basic  lead  acetates,  occurs  in 
commerce  as  verdigris.  It  is  a  bluish  or  greenish  crystalline  powder 
insoluble  in  water,  which  is  obtained  when  copper  plates  are  exposed 
to  vinegar  or  wine  residues,  undergoing  acetic  acid  fermentation  in 
air.  Verdigris  is  produced  in  a  similar  manner  when  foods  con- 
taining vinegar  or  undergoing  acid  fermentation  are  kept  in  copper 
vessels  (p.  237). 

Cupric-aceto-arsenite,  Cu(As02)2+Cu(C2H302)2,  Schweinfurter  green, 
is  a  beautiful  green  poisonous  powder,  used  as  a  paint. 

Zinc  acetate,  Zn (0211302)2 +  2H2O,  is  obtained  by  dissolving  zinc  oxide 
in  acetic  acid.  It  forms  white  shining  plates,  which  are  soluble  in  water 
and  alcohol. 

Ethyl  acetate,  acetic  ether,  acetic  acid  ethyl  ester,  CH3~COO~C2H5, 
is  obtained  by  distilling  dry  sodium  acetate  with  ethyl  alcohol  and 
sulphuric  acid.  It  is  a  colorless,  readily  inflammable  liquid  with  a 
refreshing  odor,  having  a  specific  gravity  of  0.90  and  boiling  at  74°. 

Acetyl  acetic  acid,  aceto-acetic  acid,  diacetic  acid,  ^-ketobutyric 
acid,  C4H8O3  or  CH3~CO~CH2~COOH  (acetic  acid  in  which  a  hydrogen 
atom  of  the  methyl  group  is  replaced  by  the  acetyl  radical,  CH3~C0~). 
It  is  obtained  from  its  esters  (see  below)  as  a  thick  acid  liquid, 
miscible  with  water  and  readily  decomposing  into  COj  and  acetone, 
CH3~CO~CH3,  on  warming.  Its  salts  and  esters  are  colored  violet-red 
with  ferric  chloride.  The  potassium  and  sodium  salts  are  sometimes 
found  in  the  urine  of  diabetics,  etc. 

Ketonic  Adds  in  General.  1.  Ketonic  acids  have,  as  they  contain  the  CO 
group  besides  the  COOH  group,  the  character  of  an  acid  as  well  as  a 
ketone.  We  differentiate  between  a-,  /9-,  7--ketonic  acids  (p.  329"),  depend- 
ing upon  the  nearness  or  remoteness  of  the  CO  group  to  the  COOH  group. 
The  /?-ketonic  acids  readily  decompose  into  COg  and  the  corresponding 
ketone. 

2.  Ketonic  acids  are  converted  into  the  corresponding  alcohol  acid  by 
nascent  hydrogen: 

CH3-CO-CH2-COOH  +  H2=  CH3-CH(0H)-CH -COOH. 

/?-oxybutyric  acid 


ETHANE  AND  ITS  DERIVATIVES.  365 

3.  Like  the  ketones  (p.  371)  they  unite  with  alkali  bisulphites,  hy- 
droxy lamin,  phenylhydrazin. 

4.  Preparation.  The  a-ketonic  acids  are  prepared  from  the  cyanides  of 
the  acid  radicals  (p.  346)  by  hydrolysis: 

CH3-CO-CN  +  2H0H  =  CH3-CO-COOH  +  NH3. 
^-ketonic  acids  are  obtained  from  their  esters  (see  below)  by  saponification 
with  dilute  cold  caustic  alkali,     /--ketonic  acids  (see  Levulinic  Acid)  are 
prepared  from  the  /?-ketonic  acids  with  a-halogen  fatty  acids  (p.  366,  4c). 

Acetyl  Acetic  Acid  Ethyl  Ester,  acetoacetic  ester,  /?-ketobutyric 
acid  ethyl  aster,  CH3  •  CO  •  CHj  •  COO  •  C2H5.  (In  regard  to  preparation 
see  p.  366,  8.)  It  forms  a  neutral  liquid  with  a  fruit-hke  odor,  boiling 
at  181°,  and  is  only  very  slightly  soluble  in  water. 

Acetoacetic  ester  has,  like  all  /?-ketonic  acid  esters,  great  importance 
for  chemical  syntheses,  as  the  one  H  atom  of  the  methylene  group  can 
be  readily  replaced  by  sodium  and  this  then  replaced  in  turn  by 
various  radicals  by  the  action  of  different  organic  halogen  compounds. 
The  second  H  atom  of  the  methylene  group  can  be  made  to  follow 
the  same  procedure,  and  the  compounds  obtained  can  be  made  to 
spUt  in  two  ways  by  heating  with  caustic  alkalies;  thus  into  alkyl 
ketones  (ketone  cleavage)  or  alkyl  acetic  acids  (acid  cleavage). 

Acetoacetic  ester  shows  besides  this,  like  all  ^-ketonic  acid  esters, 
the  phenomena  of  tautomerism  (p.  300) ;  hence  it  follows  that  deriva- 
tives with  ketone  structure  as  well  as  with  "enol"  structure  (p.  338) 
may  be  formed.  For  example,  if  an  acid  chloride  is  allowed  to  act 
upon  the  sodium  compound  of  the  acid,  we  obtain  a  derivative  with 
ketone  structure:  CH3-CO-CH(CH3-CO)-COO-C2H5;  while  if  an 
acid  chloride  is  allowed  to  act  upon  a  mixture  of  acetoacetic  ester 
with  pyridin,  we  obtain  a  derivative  with  "enol"  structure: 
CH3-C(CH3-CO)  =CH-COO-C2H5. 

The  p-ketonic-acid  Esters  in  General.  1.  In  the  cold  the  alkali  salt  of 
the  5-ketomc  acids  are  formed  by  the  action  of  dilute  aqueous  caustic 
alkali,  and  from  these  the  /9-ke tonic  acid  can  be  set  free  by  treatment  with 
the  proper  quantity  of  sulphuric  acid  and  isolated  by  shaking  with  ether. 

2.  On  boiling  with  dilute  aqueous  caustic  alkali  or  with  dilute  sul- 
phuric acid  a  ketone  is  obtained  besides  alcohol  and  carbon  dioxide  (ketone 
cleavage) : 

CH3-CO-CH(CH3)-COO-C,H«  +  2KOH= 

CH3-CO-CH2-CH3 + K2CO3 + C^Hg-  OH. 

3.  On  boiling  with  concentrated  alcoholic  caustic  alkali  two  acids  (or 
their  alkali  salts)  are  obtained  besides  alcohol.  One  of  these  acids  is 
always  acetic  acid  (or  CO2)  (acid  cleavage) : 

CH3-CO-CH(CH3)-COO-C2H5  +  2K0H  = 
CHrCOOK + CHrCHrCOOK  +  C2H5OH. 


366  ORGANIC  CHEMISTRY, 

4.  By  the  aid  of  their  sodium  compounds  a  great  many  syntheses  are 
possible,  of  which  the  following  are  the  most  important: 

a.  If  ethyl  iodide  is  allowed  to  act  upon  the  above,  the  Na  is  replaced 
by  ethyl,  and  in  this  compound  the  second  hydrogen  can  be  replaced  by 
sodium,  and  this  again  replaced  by  an  alcohol  radical: 

CH3-CO-CH(C2H5)-COO(C2H5),  ethylacetoacetic  ester; 
CH3-CO-C(C2H5)2-COO(C2H3),  diethylacetoacetic  ester. 

h.  By  the  action  of  acid  chlorides  the  corresponding  acid  combina- 
tions are  produced: 

CH3-CO-CH(CH3CO)-COO(C2H6),  diacetoacetic  ester; 
CH3-CO-C(CH3CO)2-COO(C2H5),  triacetoacetic  ester. 

c.  By  the  introduction  of  chlorinated  esters  we  obtain  di-  and  tri-basic 
acids: 

CHg-CO-CHNa-COO-CgHs + CH2Cl-COOC2H5= 

NaCl+CH3-CO-CH^^Q5"^(?g~^2H5  (acetylsuccinic  acid  ethyl  ester). 

If  a  halogen  fatty  acid  esters  are  used  in  the  above,  we  obtain  the 
r-ketonic  acids  as  the  product;  thus,  from  acetylsuccinic  acid  ethyl  ester 
we  get  CH3-CO-CH2-CH2-COOH  (levulinic  acid) +C2II5-OH+CO2. 

d.  Two  molecules  of  the  ester  may  be  united  by  means  of  ethylene 
bromide: 

CH3-CO-CH-COO-C2H5 

>C2H 
CH3-C0-CH-C00-C2H„. 

5.  The  compounds  given  above  as  ketone  derivatives  may  also  be 
obtained  under  certain  circumstances  as  the  enol  derivatives  (p.  338). 

6.  The  H  atoms  of  the  methylene  group  are  replaceable  by  NHj,  2NH-, 
CI,  2C1,  =NOH,  =NH,  etc. 

7.  With  aldehyde  ammonias,  anilines,  phenols,  phenylhydrazins,  we 
obtain  compounds  of  the  pyridin,  chinolin,  cumarin,  pyrazol  groups  with 
the  elimination  of  water  or  of  alcohol. 

8.  Preparation.  Sodium  ethylate  is  heated  with  the  acid  ester,  the 
sodium  compound  decomposed  by  the  addition  of  the  corresponding 
quantity  of  acetic  acid,  and  the  ester  split  off  purified  by  distillation: 

C2H5-ONa  +  2CH3-COO-C2H5= CH3-CO-CHNa-COOC2Hs  +  2C2H5-OH. 

Sod  ethylate.  Ethyl  acetate  Sodiumacetoacetic  ester. 

C2H5-ONa  +  CH3-COO-C2H6  +  CeHr  000-0^^,= 

Ethyl  acetate.         Benzoic  acid  ethyl  ester. 

C6H5-CO-CHNa-COO-C2H,  +  2C2H5-OH. 
Sodium  benzoylacetic  ester. 

If  one  of  the  esters  used  is  a  formic  acid  ester,  then  aldehyde  acid  esters 
are  obtained:  CsH.-ONa  +  H-COOC2H5  +  CH3-C00-aHB= 

Ethyl  Ethyl 

formate.  acetate. 

H-CO-CHNa-COO-C2H,  +  2C2HrOH. 

Sodium  formyl  acetic  ester. 


ETHANE  AND  ITS  DERIVATIVES,  367 

Acetyl  chloride,  CHj~COCl,  is  prepared  by  the  distillation  of  phos- 
phorus trichloride  with  acetic  acid :  3CH3COOH+  PCI3  =  3CH3-COCI+ 
H3PO3.     It  is  a  colorless,  irritating  liquid  boiling  at  55°. 

The  Acid  Halogenides  in  General.  1.  They  are  irritating,  fuming 
liquids  which  readily  exchange  their  halogens  for  other  elements  or 
radicals. 

2.  On  boiling  with  water  they  yield  the  original  acid : 

CH3-COCI  +  HOH  =  CH3-  COOH  +  HCL 

3.  With  alcohols  they  form  esters : 

CH3-COCI  +  C2H5  -  OH  ^CHs-COO-CaHg  +  HCL 

4.  With  ammonia,  acid  amides  are  produced: 

CH3COCI  +  NH3 =CH3-C0-  NH2  +  HCL 

5.  When  heated  with  salts  of  organic  acids  they  form  acid  anhydrides: 

CH3-COCI  +  CHg-COONa  =  (CHgCO)^  +  NaCL 

6.  Ketones  or  tertiary  alcohols  are  formed  with  zinc  alkyls. 

7.  Preparation.     In  the  same  manner  as  acetyl  chloride. 

Acetyl  oxide,  acetic  anhydride,  (CH3CO)20,  prepared  from  acetyl 

chloride  and  sodium  acetate  (see  above,  5),  is  a  colorless  liquid  with 

an  odor  like  acetic  acid  and  boiling  at  180°.     It  does  not  at  first  mix 

with  water,  but  gradually  it  decomposes  into  acetic  acid  therewith: 

CH3-CO-O-OC-CH3+  H2O  =  2CH3-COOH. 

The  Acid  Anhydrides  in  General.  1.  They  are  liquids  or  solids  having 
a  neutral  reaction  and  soluble  in  alcohol  and  ether. 

2.  With  water  they  are  transformed  gradually  into  the  free  acid,  and 
with  alcohols  they  form  the  esters  of  these  acids : 

(C2H302)20  +  2C2H5-OH  =2C2H,(C2H302)  +H2O. 

3.  Preparation.  They  cannot  be  prepared  by  simply  abstracting  water 
from  the  acids,  for  instance  by  P-O,,  but  are  obtained  from  the  alkali  salts 
of  the  acids  by  the  action  of  acid  chlorides  (see  Acid  Chlorides,  5). 

Acetamide,  CH3~CO~NH2,  forms  colorless  crystals  which  melt 
at  78°  and  boil  at  222°  and  are  readily  soluble  in  water  and  alcohol. 

The  Amides  in  General.  1.  They  are  generally  cry stallizable,  volatile 
bodies.  The  primary  amides  are  neutral  in  reaction,  but  as  they  contain 
the  basic  am^do  group,  they  unite,  like  ammonia,  directly  with  acids, 
forming  salt-like  compounds:  (CH^^CO  NHp)HN03.  The  amido  group 
has  also  the  power,  due  to  the  acid  radical,  of  having  one  of  the  H  atoms 
replaced  by  metals:   (CH3-  C0-NH)2Hg,  mprcuric  acetamide. 

Secondary  and  tertiary  amides  are  indifferent  bodies. 

2,  On  boiling  with  acids  or  alkalies  they  decompose  into  their  com- 
ponents with  the  taking  up  of  water: 

CH3-CO-NH2  +  H2O  =  CH3COOH  +  NH3. 


368  ORGANIC  CHEMISTRY. 

3.  On  heating  with  phosphorus  pentoxide  they  lose  1  molecule  of  water 
and  are  converted  into  the  nitriles  (p.  330) : 

CH3-CO7N  H2  =  HgO  +  CH3-CN. 

Acetamide.  Acetonitrile. 

4.  HNO2  decomposes  the  primary  amides  in  the  same  manner  as  the 
amido-acids  (p.  369,  3). 

5.  Brominated  amides  yield  amines  (which  see)  with  caustic  alkalies. 
Q.  Pre-paration.     a.  By  the  action  of  ammonia  upon  the  esters  of  the 

organic  acids  (p.  357,  3.  c),  or  upon  the  acid  halogenides  (p.  367,  4). 
h.  By  the  dry  distillation  of  the  ammonium  salts  of  the  fatty  acids: 
CH3-COO-NH, = CH3-CO-NH2  +  H2O. 

Chloracetic  Acids.  If  chlorine  is  passed  into  boiUng  acetic  acid, 
the  hydrogen  of  the  methyl  group  is  replaced  and  we  obtain  the  follow- 
ing, according  to  the  extent  of  action: 

Monochloracetic  acid,  CH2C1~C00H,  colorless  crystals  which  melt 
at  62°  and  which  readily  deliquesce. 
/    Dichloracetic  acid,  CHCl2~C00H,  a  liquid  above  0°. 

Trichloracetic  acid,   CClg'COOH,   prepared  by  the  oxidation  of 
chloral,  forms  readily  soluble  rhombic  crystals  which  melt  at  55° 
and  which  decompose  into  chloroform  on  heating  with  caustic  alkah: 
CCI3-COOH+  KOH  =  CHCI3+  KHCO3. 

These  compounds  have  a  strong  caustic  action  and  are  trans- 
formed into  acetic  acid  again  by  hydrogen. 

The  Halogen  Fatty  Acids  in  General.  1.  Some  are  fluids  and  others 
solids  and  have  great  similarity  to  the  original  acid,  but  have  still  more 
marked  acid  character  than  the  acid  from  which  they  are  derived. 

2.  They  readily  exchange  their  halogen  for  other  elements  or  radicals 
and  hence  serve  In  the  preparation  of  acids  containing  the  -NO^,  "NILy 
-OH,  -CN,  -HSO3,  etc.,  groups:  CH^Cl-CGOH  +  KCxN  =CH2(CN)'C00H 
+  KC1. 

3.  In  regard  to  the  isomers  a-,  ,5-,  etc.,  acids  see  p.  330. 

4.  Preparation.  By  the  direct  action  of  halogens  upon  fatty  acids  or 
of  HCl,  HBr,  HI,  on  the  oxyfatty  acids : 

■  CH2(OH)COOH  +  HI=CHJ-COOH  +  HA 

Oxyacetic  acid,  glycollic  acid,  CH2(0H)C00H,  is  obtained  on  warm- 
ing monochloracetic  acid  with  alkali  hydrates : 

CH^CICOOH  +  KOH  =CH,(OH)COOH  +  KCl. 

Oxyacetic  acid  is  the  first  member  of  a  new  series  of  acids  whose  mem- 
bers are  all  obtained  in  the  same  manner  from  chlorinated  fatty  acids  and 
which  will  be  considered  witli  the  divrdent  compounds. 

Thioacetic  acid,  thiacetic  acid,  CH^-COSH,  is  obtained  by  the  action 
of  P2S5  upon  acetic  acid  and  is  a  colorless  liquid  boiling  at  100°  and  smell- 
ing like  acetic  acid  and  HgS,  into  which  it  decomposes  with  water. 


ETHANE  AND  ITS  DERIVATIVES.  369 

Amidoacetic  acid,  glycocoll,  glycin,  glue-sugar,  CH2(NHj)~C00H, 
is  obtained  by  warming  monochloracetic  acid  with  ammonia: 
CH2GI-COOH+  NH3  =  CH2NH,-C00H+ HCl. 

It  can  also  be  obtained  with  other  bodies  from  hippuric  acid  (which 
see),  toluric  acid,  phenaceturic  acid,  bile-acids,  silk,  spongin,  and  glue 
(hence  the  name  glycocoll)  by  boiling  with  acids  or  alkahes.  Uric 
acid  decomposes  into  urea  and  glycocoll  on  heating  with  HI.  Amido- 
acetic acid  is  a  colorless  solid  crystallizing  in  rhombic  crystals  which 
melt  at  170°  and  which  decompose  at  higher  temperatures.  It  is  soluble 
in  water,  giving  a  sweetish  taste  thereto. 

The  Amido-acids  in  General.  1.  They  are  colorless,  mostly  crystalliza- 
ble,  neutral  solids  which  give  salt-like  combinations  with  acids  as  well  as 
bases.     Many  are  produced  in  the  putrefaction  of  glue  and  protein  bodies. 

2.  They  differ  from  the  am'des  in  that  the  amido-group  is  firmly  united 
(like  the  amines)  and  cannot  be  split  off  by  boiling  with  caustic  alkalies. 

3.  By  the  action  of  nitrous  acid  they  (like  the  amides  and  amine  acids) 
exchange  OH  for  NHg;  thus, 

CH2(NH2)-COOH  +  HNO2  =  CH2(0H)C00H  +  2N  +  H^O. 

4.  If  nitrous  acid  is  allowed  to  act  upon  their  esters,  then  isodiazo  fatty 
acid  esters  are  produced.  These  may  be  considered  as  fatty  acid  esters  in 
which  two  H  atoms  are  replaced  by  the  -N=N-  group  (see  Diazo  Com- 
pounds) : 

(CH3)-OOC-CH,(NH2)  +  HNO,  =  (CH,)OOC-  CH(N=N)  +  2HA 

Amidoacetic  acid  methyl  ester.  Isodiaz'oacetic  acid  methyl  ester 

5.  Preparation.  By  heating  the  monohalogen  fatty  acids  with  ammo- 
nia or  by  the  reduction  of  the  corresponding  nitro  fatty  acid  with  hydrogen. 

Methylamidoacetic  acid,  sarcosin,  C3H7NO2,  is  obtained  by  warm- 
ing monochloracetic  acid  with  methylamine,  NH2(CHj) : 

CH^Cl  CH2N(CH3)H 

I  +NHrCH,»   1  +HC1; 

COOH  COOH 

also  by  heating  creatine,  theobromine,  caffeine  with  barium  hydroxide. 
It  is  a  colorless  neutral  solid  crystallizing  in  rhombic  crystals  which 
are  soluble  in  water  and  melt  at  215°  and  are  volatile  without  decom- 
position at  higher  temperatures. 

Betaine,  lycin,  oxyneurine,  C^Hj^NOj  or  CH2-N(CH3)3,  is  the  internal  an- 

co— O 

hvdride  of  tnmethylhydroxylamidoacetic  acid:  H00OCHj-N(CH  )  (OH) 
It  IS  a  heterocarbocyclic  compound  (p.  326),  and  forms  the  type  of  a  series 
of  similarly  constituted  compounds  which  have  been  called  betains  (see 


370  ORGANIC  CHEMISTRY. 

Trigonellin).  It  is  prepared  by  the  careful  oxidation  of  choline  and  is  found 
in  the  cotton-seed,  buckthorn,  in  the  sugar-beet  and  hence  also  in  the 
molasses  from  beet-root  sugar,  occurring  also  as  a  non-poisonous  ptomaine. 
It  forms  colorless  deliquescent  crystals  which  on  heating  evolve  trimethyl- 
amine  (preparation  of  this  last  from  beet-root  molasses). 

Glycocholic  acid,  C2,H43NOj,  occurs  in  ox  and  human  bile,  and  decom- 
poses on  boiling  with  water  or  alkalies  into  glycocoll  and  cholalic  acid: 
CajH^gNO-  +  H,0  =  C^H jNOa  +  Cj^H.^Oj.  It  forms  crystaUine  needles  which 
are  insoluole  in  water  but  soluble  in  alcohol. 

Hyoglycholic  acid,  CjrH^gNOg,  occurs  in  pig  bile  and  decomposes  when 
treated  as  above  into  glycocoll  and  hyocholalic  acid  (see  below), 

Cholalic  or  cholic  acids  are  the  monobasic  acids  of  unknown  constitu- 
tion which  with  glycocoll  and  taurin  (which  see)  form  the  bile-acids,  which 
are  found  combined  with  alkalies  in  the  bile  (xoX?)).  Free  cholalic  acids 
are  found  in  the  intestine  and  urine  in  jaundice. 

The  cholalic  acids  of  human  and  ox  bile,  C^tB-^^O^,  of  pig  bile  (hyocho- 
lalic (lc^d,C^H.^JJ^),  of  goose  bile  (chenocholalic  acid,  C27H44O4) ,  as  well  as 
the  choleic  acid,  C25H42^4>  found  in  ox  bile  and  fellic  acid,  C23H40O4,  found 
in  human  bile,  form  monobasic,  colorless,  bitter  crystals  which  are  diffi- 
cultly soluble  in  water  and  ether  but  readily  soluble  in  alcohol,  and  this 
solution  having  a  dextrorotatory  power.  They  differ  from  each  other  by 
their  melting-point.  On  boiling  with  acid,  by  putrefaction  in  the  intestine 
or  by  heating,  they  loose  water  and  are  converted  into  amorphous  com- 
pounds, the  dyslysines,for  example,  C.^HggOg,  which  are  insoluble  in  water 
and  alkalies.  The  cholalic  acids  and  their  compounds,  the  bile  acids,  give 
Pettenkofer's  reaction,  which  consists  in  treating  the  solution  with  two- 
thirds  volume  concentrated  sulphuric  acid,  so  that  the  temperature  does 
not  rise  above  60°,  and  then  adding  3  to  5  drops  of  "a  cane-sugar  solution 
(or  f urfurol) ,  when  a  beautiful  violet  coloration  is  obtained. 

7.  Propane  and  its  Derivatives. 

Propane,  propyl  hydride,  CgHg  or  CH3~CH2~CH3  (p.  340).  Two 
series  of  isomeric  compounds  are  derived  from  the  above,  depending 
upon  whether  the  CHg"  or  the  CHj"  group  is  substituted.  In  the 
first  case  we  obtain  the  normal  compounds  and  in  the  second  case  the 
isopropyl  compounds. 

Normal  or  primany  propyl  alcohol,  CgHgO  or  CHg-CHrCH^OH, 
is  formed  in  the  fermentation  of  certain  forms  of  sugars  and  wine 
residues  and  can  be  separated  from  the  fusel-oil  (p.  354)  by  fractional 
distillation.  It  is  a  colorless,  pleasant-smelling  liquid  which  boils  at 
96°  and  yields  propylaldehyde  and  propionic  acid  on  oxidation. 

Propyl  aldehyde,  CgHeO  or  CH3-CH0-CHO,  is  obtained  on  the  oxida- 
tion of  propyl  alcohol  or  by  the  distil'ation  of  formic  acid  with  salts  of  pro- 
pionic acid  (p.  351,  12).  It  forms  a  liquid  similar  to  ethyl  aldehyde  and 
boils  at  49°. 

Propionic  acid,  CjHeOj  or  CH3-CH2-COOH,  is  found  in  perspira- 
tion, gastric  juice,  in  the  fruit  of  the  Gingko  biloba,  in  the  fly-agaric, 


PROPANE  AND  ITS  DERIVATIVES.  371 

in  crude  wood  vinegar,  and  in  the  mineral  water  of  Weilheim  and 
Briickenau.  It  is  prepared  by  the  oxidation  of  propyl  alcohol  or 
from  ethyl-cyanide  (p.  346,  2).  It  is  a  strong  irritating  liquid,  boiling 
at  141°  and  readily  soluble  in  water.  It  can  be  separated  from  its 
watery  solution  as  a  liquid  swimming  on  the  surface  by  the  addition 
of  calcium  chloride  thereto.  This  property  and  the  fact  that  its 
salts  have  a  fatty  touch  is  the  origin  of  its  name  (ytpcSroy,  the  first; 
ntor,  fat). 

a- Amido propionic  acid,  alanin,  CH3-CH(NH^)-C00H,  is  a  cleavage 
product  of  the  proteids  and  forms  needles  which  melt  at  250°. 

/?-Acetylpropiomc  acid,  levulinic  acid,  CHg-CO-CHj-CHj-COOH  (p. 
366,  c),  is  obtained  on  boiling  most  carbohydrates  with  dilute  hydrochloric 
or  sulphuric  acids,  forming  colorless  plates  which  melt  at  33°. 

Secondary  or  isopropyl  alcohol,  CH3~CH(OH)~CH3,  is  prepared 
according  to  the  general  methods  (p.  344)  and  is  a  colorless  liquid 
boiling  at  83°. 

Dimethyl  ketone,  acetone,  CjHgO  or  CH3~C0~CH„  is  found  in 
small  quantities  in  human  urine,  in  the  blood,  transudations  and 
exudations,  and  in  larger  quantities  in  the  urine  of  diabetics.  It  is 
formed  in  the  gentle  oxidation  of  isopropyl  alcohol  and  in  the  dry  dis- 
tillation of  tartaric  acid,  citric  acid,  sugar,  wood,  and  hence  occurs 
also  in  crude  wood  alcohol.  Ordinarily  it  is  obtained  by  the  dry 
distillation  of  sodium  or  calcium  acetate  (p.  372,  8). 

It  is  a  colorless  liquid,  smelling  like  peppermint,  and  boiling  at 
56°.  It  is  soluble  in  water,  etc.,  and  on  oxidation  it  decomposes  into 
acetic  acid  and  carbon  dioxide : 

CH3-CO-CH3+  40  =  CH3-COOH+  H,0+  COj. 
With  iodine  solution  and  caustic  alkali  it  yields  iodoform  (p.  347). 
Adetone  is  condensed  by  hydrochloric  acid  gas  or  by  concentrated 
sulphuric   acid: 

2C3HeO=  H2O+ (CH,)rC=CH-C0-CH3  (Mesityl  oxide); 
SCgHgO  =2H20+  (CH3)2=C=CH-CO-CH=C-(CH3),  (Phoron) ; 
3C3HeO=3H20+CeH,2  (Mesitylene). 

The  Ketones  in  General.  1.  They  are  similar  in  physical  properties  to 
the  aldehydes,  also  in  their  behavior  towards  acid  alkali  sulphites,  hydro- 
cyanic acid,  and  phenylhydrazin,  but  they  do  not  reduce  ammoniacal  silver 
solutions  (p.  350,  1). 

2.  They  do  not  combine  with  alcohols,  but  on  the  contrary  they  com- 
bine with  mercaptans  with  the  elimination  of  water  and  the  formation  of 
mercaptals,  which  are  analogous  to  the  mercaptols  (p.  351,  8): 
CH3-CO-CH3 + 2C2H5-  SH  =  (CH3)2=C= (SC^^j), + H2O. 


372  ORGANIC  CHEMISTRY. 

3.  With  hydroxylamin  they  form  oximide-  or  isonitroso-compounds, 
which  are  called  acetoximes: 

CH3-CO-CH3  +  NH20H=(CH3)2-=C=N-OH+H20  (p.  351,7). 

4.  By  nascent  hydrogen  they  are  transformed  into  secondary  alco- 
hols. In  these  reactions  we  have  side  products  produced  in  that  each  two 
molecules  of  the  ketone  unite  together,  forming  divalent,  ditertiary  alco- 
hols (see  Glycols),  which  are  called  pinacones: 

2CH3-CO-CH3  +  H2=  (CH3)rC(OH)-C(OH)=(CH3)2. 
6.  They  cannot  be  polymerized,  but  on  the  contrary  suffer  condensa- 
tions readily  (see  Dimethylketone). 

6.  On  oxidation  the  ketor;es  yield  acids  which  contain  less  carbon 
atoms  in  the  molecule  (p.  334). 

7.  With  ammonia  they  form  ketonamines,  whereby  2  or  3  molecules  of 
the  ketone  combines  with  1  molecule  of  ammonia,  with  the  elimination  of 
H2O  :(CH3)2=C(NH2)-CH2-CO-CH3,  diacetonamine. 

8.  Preparation,     a.  By  the  oxidation  of  secondary  alcohols. 

h.  By  the  dry  distillation  of  fatty  acid  salts:  2CH3-COONa= 
CH3-CO-CH3  +  Na2C03.  If  a  mixture  of  two  salts  is  used  we  obtained  a 
mixed  ketone  (with  two  different  alcohol  radicals):  CH3~C00Na-f 
C2H,-COONa=CH3-CO-C2H5  +  Na2C03.  With  formates  we  always  ob- 
tain aldehydes  instead  (p.  351,  12). 

c.  By  the  action  of  acid  chlorides  upon  zinc  alky  Is  (p.  367) : 

2CH3-COCl+Zn(CH3)2  =2CH3-CO-CH„  +ZnCl2; 
2CH3-COCI  +  Zn(C3H7)2=  2CPI3-CO-C3H7  +  ZnClj. 

d.  From  the  acetoacetic  esters  by  caustic  potash  (p.  365,  2). 
Disulfonethyldimethylmethane,  (CH3)2=C=(S02~C2H6)2,  sulfonal,  melts 

at  126°;  also 

Disulfonethylmethylethylmethane,  (CH^)  (C2H5)=C-  (S02-C2H6)2.  methyl 
sulfonal,  trional,  melts  at  76°,  and 

Disulfonethyldiethylmethane,  (C2H5)2=C=(S02-C2H5)2,  tetronal,  which 
melts  at  85°;  all  three  form  colorless  and  tasteless  crystals,  difficultly 
soluble  in  water,  and  when  heated  with  carbon  powder  yield  the  char- 
acteristic odor  of  the  mercaptans.  They  are  obtained  by  the  oxidation 
of  the  corresponding  mercaptols,  which  are  produced  from  acetone  and 
mercaptans  (p.  371,  2). 

8.  Butane  and  its  Derivatives. 
Butanes,  C4H10.     Two  are  known.     On  substituting  one  H  atom 
by  monovalent  elements  or  radicals  we  have  4  isomers  possible.    Thus 
on  the  introduction  of  HO  group  we  have  4  alcohols,  all  of  which  have 
been  prepared: 

CH3    CH,      CH3    CH,      CH,    CH, 

CH  CH  COH 


CH, 
CH, 
CH, 

CH,           CH, 

CH,           CH, 

CH,           CHOH 
1 

CH, 

Butane. 

CH,OH      CH3 

Primary.     Secondary. 
Butyl  alcohol. 

CH,  (Jh^OH         CH, 


Isobutane.  Primary.  Tertiary. 

Isobutyl  alcohol. 


BUTANE  AND  ITS  DERIVATIVES.  373 

Primary  butyl  alcohol,  C4HioO,  occurs  in  fusel-oil,  especially  with 
wine-yeast  fermentation,  and  is  prepared  according  to  the  general 
methods  (p.  344) ;  also  from  glycerine  by  schizomycetes  fermentation. 
It  is  a  hquid  boiling  at  117°,  with  a  pleasant  odor. 

Butyric  acid,  ethylacetic  acid,  fermentation  butyric  acid, 
CH3~CH2~CH2~COOH  or  C4H8O2.  Occurrence.  It  occurs  as  glycerine 
ester  to  a  slight  extent  in  butter,  in  cod-liver  oil,  croton-oil,  in  the 
fruit  of  the  tamarind,  of  the  soap  tree,  and  of  Ginko  biloba.  Its 
alkyl  esters  also  occur  in  the  ethereal  oils  of  different  Compositse 
and  Umbelhferse;  it  occurs  free  in  rancid  butter,  in  the  juice  of 
the  caterpillar,  perspiration,  and  cheese,  combined  with  bases  in  the 
fluid  of  the  spleen,  muscle,  and  in  the  contents  of  the  large  intestine 
and  pathologically  in  the  gastric  juice.  It  is  formed  by  a  special 
fermentation  of  sugar,  starch,  lactic  acid;  also  in  the  putrefaction 
and  oxidation  of  proteids.  It  is  therefore  found  in  sauerla-aut,  in 
sour  pickels,  in  spent  tan,  in  Limburger  cheese,  etc. 

Preparation.     1.  According  to  the  general  methods  (p.  346). 

2.  Ordinarily  it  is  prepared  by  a  special  fermentation  of  sugars, 
starch,  dextrins,  or  glycerine  by  mixing  them  with  water,  chalk,  and  old 
cheese  and  allowing  this  to  stand  for  a  long  time  at  30-40°.  The 
liquid  becomes  gradually  thicker  and  finally  solidifies,  with  the  forma- 
tion of  calcium  lactate,  Ca (0311503)2,  and  if  this  is  allowed  to  stand 
longer  it  becomes  again  fluid,  with  the  evolution  of  carbon  dioxide 
and  hydrogen,  and  as  soon  as  the  development  of  gas  ceases  all  the 
lactic  acid,  CgHeOg,  has  been  transformed  into  butyric  acid: 
2C3H0O2  =  CJi.O,  +  4H+2CO2. 

Lactic  acid.     Butyric  acid. 

On  distillation  with  sulphuric  acid  the  butyric  acid  is  separated  from 
its  calcium  salt. 

The  fermentation  above  mentioned  is  brought  about  by  the  lactic 
acid  and  butyric  acid  organisms,  the  mixed  spores  of  which  exist 
in  the  cheese.  The  fermentation  is  stopped  by  an  excess  of  free  acid, 
hence  calcium  carbonate,  zinc  oxide,  etc.,  are  added  in  order  to  form 
neutral  salts.  If  we  make  use  of  pure  lactic  or  butyric  acid  bacilli 
instead  of  the  cheese  we  obtain  lactic  or  butyric  acids  immediately. 

Properties.  Butyric  acid  is  a  colorless  liquid  boiling  at  163°  with  a 
peculiar  odor,  especially  unpleasant  when  dilute.  It  is  soluble  in 
water  in  all  proportions.    Calcium  butyrate,  Ca(C4H702)2+H20,  is 


374  ORGANIC  CHEMISTRY. 

less  soluble  in  hot  water  than  in  cold  and  hence  separates  out  from 
concentrated  watery  solutions  on  boiling. 

Isobutyl  alcohol,  (CH3)j^CH~CH20H,  occurs  in  fusel-oil,  especially 
from  beer-yeast,  and  is  a  colorless  Hquid  having  an  odor  similar  to 
fusel-oil  and  boiling  at  107°.  On  oxidation  it  yields  isobutylaldehyde 
and  then  isobutyric  acid. 

Isobutyric  acid,  (CH3)2'"CH~COOH,  is  found  free  in  carobs 
(Ceratonia  siliqua),  in  the  oil  of  Pastinaca  sativa,  in  feces,  and  in  the 
putrefactive  products  of  proteids;  it  exists  as  ester  in  Roman  cam- 
omile-oil. It  is  a  colorless  liquid  with  an  unpleasant  odor  similar 
to  butyric  acid  and  boiling  at  154°.  It  is  soluble  in  5  parts  water. 
Calcium  isobutyrate,  Ca(C4H702)2+5H20,  is  more  soluble  in  hot 
water  than  in  cold. 

9.  Pentane  and  its  Derivatives. 

Pentanes,  C5H12.  The  three  possible  pentanes  are  known,  from 
which  eight  structural  isomeric  alcohols  are  derived,  all  of  which 
are  known.  The  four  primary  pentyl  alcohols  have  correspondingly 
four  pentyl  acids. 

Isopentyl  alcotiol,  ordinary  amyl  alcohol,  fermentation  amyl 
alcohol,  C5H12O  or  (CH3)j=CH~CH2~CH20H,  occurs  as  ester  in 
Roman  camomile- oil  and  is  the  chief  constituent  of  fusel-oil,  of 
potato  spirits  (p.  354),  from  which  it  is  obtained  by  fractional  dis- 
tillation. It  is  a  colorless,  poisonous,  inactive  liquid,  boiling  at 
132°  and  with  a  characteristic  odor.  It  is  soluble  in  40  parts  water 
and  the  vapors  cause  coughing.  Its  esters  are  used  in  the  making  of 
confectionery,  cordials,  etc. ;  thus  amyl  valerianate  as  apple-oil,  amyl 
acetate  as  pear-oil,  etc.  (see  Esters,  p.  357). 

Amyl  alcohols,  (CH3)(C,H5)-CH-CH20H.  Three  are  known;  the 
Isevorotatory  modification  is  also  found  in  fusel-oil,  the  dextrorotatory 
one  prepared  artificially,  and  the  inactive  modification  obtained  on  mix- 
ing the  other  two  (p.  39). 

Amyl  nitrite,  C5H„~0~N0,  is  produced  on  passing  nitrous  acid 
into  hot  amyl  alcohol,  from  which  amyl  nitrite  can  be  distilled  off  as 
a  yellowish  hquid,  having  a  specific  gravity  of  0.88,  boiling  at  98°, 
and  with  a  fruit-like  odor;  when  inhaled  causes  an  increased  flow 
of  blood  to  the  head. 

Valeric  acid,  C5H,„02  or  (CH3)2-CH"-CH2-COOH,  propylacetic 
acid.     Occurrence.     Free    and   as  ester   in   the  blubber  of  the  Del- 


COMPOUNDS  WITH  MORE  THAN  FIVE  CARBON  ATOMS.  375 

phinus  globiceps,  cheese,  perspiration  of  the  feet,  in  the  valerian 
root  (Radix  Valerianae),  in  the  angelica  root,  in  Viburnum  opulus, 
and  in  human  feces. 

Preparation.  It  was  formerly  prepared  by  the  distillation  of  the 
valerian  root,  but  now  it  is  obtained  by  the  oxidation  of  fermentation 
amyl  alcohol,  whereby  the  Isevorotatory  amyl  alcohol  (see  p.  374), 
which  is  always  present,  is  oxidized  into  Isevorotatory  valeric  acid, 
which  boils  at  172°. 

Properties.  Valeric  acid  is  a  liquid  which  boils  at  175°,  has  an 
irritating  odor  similar  to  old  cheese,  is  optically  inactive,  and  dissolves 
in  12  parts  water. 

Diamido- valeric  acid,  ornithin,  C4H7(NH2)2~COOH,  is  produced  on 
boiling  oruithuric  acid  with  concentrated  hydrochloric  acid  as  well  as  from 
arginin  (which  see)  by  boiling  with  baryta-water.  On  putrefaction  it 
yields  putrescin,  C4H8CNH2)+C02  (p.  398). 

Tertiary  amyl  alcohol,  (CH3)3=(J(OH)-CH2-CH3,  dimethyl  ethyl  car- 
binol,  is  prepared  by  distilling  calcium  hydroxide  with  amyl  sulphuric 
acid  obtained  from  isoamylene,  C^Hk,  (see  Olefines),  and  sulphuric  acid: 
(C5Hu)HS04+Ca(OH)2=CaSO;+C,H.,OH  +  H20.  It  is  a  colorless  liquid 
boiling  at  102.5°  and  having  an  odor  similar  to  camphor. 

lo.  Compounds  with  more  than  Five  Carbon  Atoms. 

As  the  number  of  isomers  greatly  increases  with  an  increase  in  the 
carbon  atoms  (p.  301)  only  the  most  important  compounds  will  be 
treated  from  now  onward. 

a.  Alcohols. 

From  hexyl  alcohol  on,  the  alcohols  are  soluble  in  water  with  difficulty 
or  are  insoluble.  From  cetyl  alcohol  on,  only  solid  alcohols  are  known 
and  the  best  known  are  mentioned  below. 

Hexyl  alcohol,  CbHjP,  occurs  as  hexylbutyrate  in  the  essential  oil  of 
Heracleum  giganteum. 

Heptyl  alcohol,  CyHigO.  Thirty-eight  isomeric  alcohols  with  this 
formula  are  possible  and  thirteen  of  these  have  been  already  prepared 
artificially. 

Octyl  alcohol,  CgHigO,  occurs  as  ester  in  the  ethereal  oil  of  Heracleum 
sphondvlium,  Pastinaca  sativa,  Heracleum  giganteum. 

Cetyl  alcohol,  ethal,  CjgHg^O,  forms  the  chief  constituent  of  spermaceti 
as  cetyl  palmitate  and  is  found  in  the  coccygeal  glands  of  the  goose  and 
duck.     It  is  a  white  crystalline  solid,  melting  at  50°. 

Cetin,  spermaceti,  is  obtained  from  the  cranial  cavity  of  the  pot- 
whale,  where  it  exists  as  a  liquid  fat  and  crystallizes  on  cooling. 

Ceryl  alcohol,  cerotin,  CajH^eO,  exists  as  ceryl-cerotinate  (cerotic 
acid  ester,  p.  377)  in  Chinese  wax  (plant  wax),  and  is  a  white  crystalline 
solid,  melting  at  70°. 


376  ORGANIC  CHEMISTRY. 

Melissyl  alcohol,  myricyl  alcohol,  C^^^X),  exists  as  myricyl  palmitate 
as  the  chief  constituent  of  beeswax  (p.  377),  and  is  a  white  crystalUne 
bolid,  melting  at  85''. 

h.  Acids. 

Corresponding  to  the  preceding  alcohols  we  have  to  mention  the  follow- 
ing acids,  which  are  derived  therefrom  by  oxidation, 

Caproic  acid  melts  at  —2°,  while  all  the  higher  fatty  acids  are  solid  at 
ordinary  temperatures.  Caproic  acid  an  i  tlie  following  acids  of  the  series 
are  soluble  with  difficulty  in  water  and  from  lauric  acid  and  beyond  tiiey 
are  insoluble  in  water.  Theoretically  8  hexyl  acids  are  possible,  38  octyl 
acids,  and  507  undecyl  acids. 

Caproic  acid,  CgHjaOg,  occurs  as  ester  in  the  fruits  of  the  Gingko 
biloba,  seeds  of  Heracleum  sphondylium,  flowers  of  Satyrium  hirci- 
num,  and  is  also  formed  as  traces  in  the  butyric  acid  fermentation.  It 
is  a  liquid  boiling  as  205°  and  having  an  odor  similar  to  perspiration. 

Caprylic  acid,  CgHuOg,  is  a  crystalline  solid,  melting  at  16°,  and  having 
an  odor  similar  to  perspiration. 

Capric  acid,  CioHgoOj,  is  a  crystalline  solid  melting  at  30°  with  a  sim- 
ilar odor. 

Caproic,  caprylic,  and  capric  acids  occur  as  glycerine  esters  in  butter, 
in  cocoanut-oil,  and  in  many  fats.  They  also  occur  free  or  as  esters  in 
cheese,  perspiration,  fusel-oil  from  wine,  and  in  beet-root  molasses. 

Ethyl  caprinate,  with   some   ethyl   caprilate,   forms  cenanthic  ether, . 
{oivo<i,  wine),  also  called  wine-oil,  which  gives  odor  to  the  wine  (but  not 
the  bouquet),  and  is  obtained  from  wine-yeast  by  distillation. 

Amidocaproic  acid,  leucine,  C5Hio(NH2)~COOH;  according  to  struc- 
ture it  is  amidoisobutyl  acetic  acid,  (CH3)2=CH-CH2-CH(NH2)-COOH. 
Occurrence.  In  river  crabs,  spiders,  butterfly  caterpillars,  lupin, 
squash  seeds,  beet-root  molasses,  pancreatic  juice,  in  all  parenchymous 
organs  and  glands,  and  also  in  the  blood  in  urine  in  certain  diseases. 

Preparation  and  Formation.  It  is  formed  in  the  putrefaction  of 
proteids  (hence  occurring  in  old  cheese  and  hence  the  old  name  cheese 
oxide)  and  is  obtained,  besides  glycocoll  (p.  369),  on  boiling  proteids  or 
gelatine  with  sulphuric  acid  or  caustic  alkahes  (Synthesis,  see  p.  369, 5). 

Properties.  Shining  crystalline  leaves  or  characteristically  formed 
balls  or  tufts  which  are  soluble  in  water  and  hot  alcohol.  According 
as  to  the  origin  of  the  material  from  which  it  is  prepared  we  have  in- 
active, dextro  or  Isevorotatory  leucin.  With  nitrous  acid  it  is  con- 
verted into  leucinic  acid:  CeH^Oa  (p.  369,  3). 

C5H,o(NH,)COOH-l-  HNO,  =  C5H,„(0H)C00H+  2N+  H,0. 

Leucinimide,  C^Hj-CIK^^gJ^QNcH-C^Hg,  is  formed  with  leucine  in 

the  decomposition  of  the  proteids. 

Diamido  caproicacid,  lysin,  C5Ug(NH2)2COOH,  is  a  cleavage  product 
of  proteins  and  on  putrefaction  yields  cadaverin,  C5Hn)(NH2)2  +  COj  (p.  398). 


COMBINATIONS   WITH  METALLOIDS.  377 

Laurie  acid,  Ci2H2402,  occurs  in  the  oil  of  laurel  as  glycerine  ester(laurm), 
forms  white  crystals  melting  at  44°. 

Myristic  acid,  Cj^HjsOa,  as  glycerine  ester  (myristin)  in  nutmeg  fat, 
wool  fat,  whale-oil;    melts  at  53°. 

Palmitic  acid,  CigHajOj,  occurs  in  large  quantities  part  as  glycerine 
ester  (palmitin)  and  part  free  in  palm-oil.  It  forms  crystalline 
masses  melting  at  62°. 

Stearic  acid,  CigligeOj,  occurs  to  the  greatest  extent  as  glycerine 
ester  (stearin)  in  the  solid  animal  fats  (the  tallows).  It  forms 
colorless  leaves  and  melts  at  69°.  Palmitic  and  stearic  acids  exist 
free  in  decomposed  pus,  cheesy  tuberculous  masses,  adipocere,  etc., 
and  combined  with  alkalies  or  calcium  in  excrements,  pus,  trans- 
udations, etc.     Stearin  candles  consist  of  stearic  and  palmitic  acids. 

The  mixed  glycerine  esters  of  palmitic,  stearic,  and  oleic  acids  (which 
see)  form  most  of  the  fats  and  their  cholesterin  esters,  the  wool  fats. 

The  alkali  salts  of  palmitic,  stearic,  and  oleic  acids  are  soluble  in 
water  and  alcohol  and  are  called  soaps.  All  their  other  salts  are 
insoluble.  In  regard  to  the  preparation  of  these  fatty  acids  on  a 
large  scale  see  Glycerine  and  Oleic  Acid. 

Arachidic  acid,  CoqR^o^^,  theobromic  acid,  occurs  as  glycerine  ester  in 
cacao-  and  earth-uut,  and  melts  at  75°. 

Behenic,  CgzH^^Oa,  exists  in  beherilc  oil  (oil  from  the  seeds  of  Moringa 
oleifera)  as  glycerine  ester  and  melts  at  76°. 

Lignoceric  acid,  Cg^H^gOj,  occurs  in  the  beech-wood  tar. 

Cerotic  acid,  CaeHr.oOg,  melts  at  78°,  and  is  found  free  in  beeswax 
and  as  ceryl  ester  ii  Chinese  or  plant  waxes. 

Melissic  acid,  CgoHgoOj,  is  obtained  from  melissyl  alcohol  by  heating 
with  soda  lime.     It  melts  at  88°. 

II.  Combinations  with  Metalloids. 

All  metalloids  form  volatile  compounds  with  the  alkyls;  these 
compounds  have  an  analogous  composition  to  their  hydrogen  com- 
pounds. Besides  these,  combinations  with  nitrogen  and  phosphorus 
are  known  which  contain  hydrogen  besides  alkyls.  The  alkyl  com- 
binations of  oxygen  (the  ethers)  and  of  sulphur  (sulpho-ethers)  have 
already  been  considered.  The  alkyl  compounds  of  nitrogen,  phos- 
phorus, arsenic,  antimony  are  called  amines,  phosphines,  arsines, 
stibines. 

a.  Compounds  of  Nitrogen. 

Amines,  amine  bases.  We  differentiate  between  the  primary  or 
amine  bases,  secondary  or  imide  bases,  and  tertiary  or  nitrile  bases 
(p.  330). 


378  ORGANIC  CHEMISTRY. 

Occurrence.  Methyl,  ethyl,  and  propyl  combinations  are  formed  in 
the  putrefaction  of  many  organic  bodies,  especially  fish,  gelatine, 
and  peptone. 

Properties.  The  amines  have  an  alkaline  reaction,  are  non-poison- 
ous, volatile  without  decomposition,  and  combine,  like  NH3,  directly 
with  acids,  forming  salts.  Their  sulphates  combine  with  aluminum 
sulphate,  formitig  alums;  their  chlorides  give  crystalline  double  salts 
with  platinum  chloride  similar  in  composition  to  that  with  ammo- 
nium chloride.  The  lower  amines  are  gaseous,  similar  to  NH3,  but 
differ  therefrom  in  being  inflammable,  or  liquids,  while  the  higher 
members  are  colorless  and  odorless  solids.  The  volatility  and  solu- 
bility in  water  decreases  with  the  increase  in  the  amount  of  carbon. 
Their  salts  differ  from  the  ammonium  salts  by  their  solubility  in 
alcohol. 

Primary  amines  yield  alcohols  when  treated  with  nitrous  acid: 
CHs-NHj  +  HNOa^CH.-OH  +  H2O  +  2N.  Secondary  amines  yield  nitros- 
amines:  (CH3)2=NH  +  HN02=  (CH3)2=N-NO  +  H20.  Tertiary  amines 
are  not  changed  at  ordinary  temperatures  by  nitrous  acid;  primary  aro- 
matic amines  give  diazo-compounds  (which  see).  Further,  in  regard  to 
the  identification  of  primary  amines  see  Isonitrile  (p.  391). 

Preparation.  1.  By  the  action  of  nascent  hydrogen  upon  the  cyan* 
alkyls  (Mendius's  reaction) : 

CH,-CN  +  4H = CH3-CH -NH2 

Acetonitrile.  Ethylamine. 

2.  On  distilling  the  ester  of  isocyanic  acid  with  caustic  alkali: 

OCN  (CH,)  +  2K0H  =  NH^CHg  +  K.COg, 

or  by  distilling  a  brominated  amide  with  caustic  alkali  (Hoffmann's  reac- 
tion), whereby  isocyanic  acid  ester  is  first  formed,  and  then  this  yields  the 
amine :   CH3-CO-NH Br  +  KOH  =  CH  "NCO  +  KBr  +  H^O. 

3.  By  the  reduction  of  the  nitro-alkyls: 

CH3-NO2  +  6H  =  CH-rNHj  +  2H2O. 

4.  On  heating  the  halogen  alkyls  with  ammonia: 

C^HJ  +  NH3=  C2H5-NH2  +  HI. 

If  the  primary  amine  thus  obtained  is  heated  again  with  alkyl  iodide  we 
obtain  a  secondary  amine,  and  this  treated  further  in  the  same  manner 
yields  a  tertiary  amine: 

C^HsI  +  NH/C^Hg)  =  HI  +  NH(aH,)2  diethylamine^ 
CaHJ  +  NH(C2Hp)2=  HI  +  N(C2H5)2  triethylamine. 

If  we  allow  an  iodide  of  another  alcohol  radical  to  act  upon  a  primary 
amine,  we  obtain  a  mixed  amine :  CH3I  +  NHo(C2H.,)  =  HI  +  NH(CH3')  (C^Hj) 
(methyl  ethylamine). 

The  HI  produced  combines  directly  with  the  amines,  forming  salts.    If 


I 


COMBINATIONS  WITH  METALLOIDS.  379 

the  hydro-iodide  of  the  amine  thus  obtained  be  distilled  with  caustic  alkali 
we  obtain  the  free  amine:   (CA)3N.HI  +  K0H=  (C2H5)3N  +  KI  +  H^O. 

Methylatnine,  NHjCCHj),  is  found  in  the  herring-brine,  in  the 
products  of  the  dry  distillation  of  animal  bodies  (in  animal  oil)  of 
wood  (in  crude  wood  alcohol),  and  is  also  formed  by  the  action  of 
nascent  hydrogen  upon  formonitrile  (hydrocyanic  acid).  It  is  a 
colorless  combustible  gas  with  an  ammoniacal  odor,  liquefiable  below 
—  6°.  It  is  the  most  soluble  of  all  gases,  1  volume  water  dissolving 
1150  volumes  at  12°;  this  solution  shows  all  the  properties  of  an 
ammonia  solution;  it  precipitates  metallic  salts,  dissolves  copper  and 
silver  salts  in  excess  but  not  cobalt,  nickel,  and  cadmium  salts. 

Trimethylamine,  ^(CHj),,  is  found  in  the  flowers  of  the  haw- 
thorn, pear  tree,  mountain  ash,  ergot,  bone-oil,  coal-tar  oil,  as  well 
as  in  the  herring-brine,  to  which  it  gives  its  odor.  It  is  formed  in 
the  putrefaction  of  animal  tissues  and  gelatine  as  well  as  in  the  dry 
distillation  of  many  organic  bodies.  It  is  obtained  by  the  distillation 
of  herring-brine  with  caustic  alkali  or  by  the  dry  distillation  of 
"  vinasse  "  from  beet-root  molasses.  It  is  a  colorless  liquid  boiling 
at  3°  and  with  a  pronounced  fishy  odor. 

Ammonium  Bases  (p.  331).  These  bases  are  derived  from  the  hypo- 
thetical ammonium  hydroxide,  NH4~0H,  in  which  all  the  hydrogen 
atoms  of  the  ammonium  group  NH4  (p.  150)  are  replaced  by  alkyls. 

Properties.  They  are  similar  to  the  alkali  hydroxides.  They  are 
soluble  in  water,  giving  a  strong  alkaline  reaction  thereto;  they  deli- 
quesce in  the  air,  saponify  fats,  precipitate  metallic  hydroxides  from 
metallic  solutions,  and  form  crystalline  salts  with  acids.  They  are 
not  volatile  without  decomposition. 

Preparation.  On  heating  the  tertiary  amines  (see  p.  378,  4)  with  the 
iodides  of  the  alcohol  radicals: 

(C2H,)3N  +  C2H5l=  (C2H,)4NI  (corresponding  to  H4NI). 
Triethylamine.  Tetraethyl  ammonium  iodide. 

The  tetra-alkyl  ammonium  salt  thus  obtained  is  not  decomposed  by  caustic 
alkali,  but  on  treating  it  with  moist  silver  oxide  the  alkyl  ammonium 
hydroxide  is  obtained,  (C2H,)4NI  +  Ag.OH=  (C2H5)4N(OH) +AgI,  which 
separates  out  on  evaporating  the  alkaline  solution  under  the  air-pump. 

Tetramethyl  ammonium  hydroxide,  (CH3)4N(OH),  forms  white  crys- 
talline, caustic  masses. 

Choline,  CgH.sN^Oa  (structure  below) ,  bilineurine,  sincalin,  trimethyl- 
oxyethyl  ammonium  hydroxide,  occurs  in  the  fly  agaric,  hops,  cotton-seed, 
herring-brine,  fresh  cadavers,  also  as  constituent  of  the  lecithins  widely 
distributed  in  the  animal  kingdom.     It  is  produced  on  boiling  ox  brains, 


380  ORGANIC  CHEMISTRY, 

yolk  of  egg,  bile,  with  Ba(0H)2,  also  from  the  alkaloids  of  the  white  mus- 
tard (sinapin)  by  boiling  with  alkalies.  Choline  can  be  prepared  artificially 
by  heating  ethylenoxide  with  trimethylamine  and  water:  N(CHy)3  + 
C2H,0  +  H20=(HO)(CHa)3N(C2H,.OH).  It  is  a  dehquescent  crystalline 
solid  which  has  a  strong  alkaline  reaction,  non -poisonous,  and  gives  good 
crystalline  salts. 

Muscarine,  oxycholine,  C5H15NO3,  is  the  poison  of  the  fly  agaric,  and  is 
also  formed  in  the  oxidation  of  choline  with  nitric  acid.  It  forms  colorless 
deliquescent  crystals. 

Neurine,  CjHigNO  or  (HO)(CH8)sN(C2H3),  trimethylvinyl  ammonium 
hydroxide  (monovalent  radical  vinyl,  CHg^CH),  is  obtained  as  a  cleavage 
product  of  the  lecithins,  respectively  of  choline.  It  is  also  obtained  in  the 
short  putrefaction  of  meat  and  fish  (see  Ptomaines)  by  the  splitting  off  of 
a  molecule  of  water  from  the  choline,  a  constituent  of  the  lecithins,  and  is 
a  difficultly  crystallizable,  deliquescent  poisonous  body. 

h.  Compounds  of  Phosphorus. 
Phosphines  and  phosphonium  bases  are  very  similar  to  the  above-men 
tioned  nitrogen  compounds  and  are  obtained  in  the  same  manner. 

Methyl  phosphine,  PH2(CH3),  is  a  neutral,  spontaneously  inflammable 
gas  having  an  extremely  unpleasant  odor. 

Tetramethyl  phosphonium  hydroxide,  P(CH  J4OH,  decomposes  on  heat- 
ing into  trimethyl  phosphine  oxide,  which  is  very  stable,  and  methane? 
P(CH3),0H  =P(CH3)30  +  CH,. 

c.  Compounds  of  Arsenic  and  Antimony. 

Arsines  and  Stibines  have  no  basic  properties  on  account  of  the  more 
metallic  character  of  these  elements,  but  on  the  contrary  have  the  property 
of  forming  compounds  with  oxygen,  sulphur,  and  halogens,  having  the 
formula  As(CH,)3  x^  (a^j =0,  S,  or  Clj).  The  arsines  and  stibines  are  there- 
fore to  be  considered  as  their  pentachlorides,  sulphides  or  oxides,  in  which 
these  elements  are  entirely  or  m  part  replaced  by  alky  Is. 

Arsonium  and  stibonium  bases  are  prepared  in  the  same  manner  as 
ammonium  and  phosDhonium  bases  and  are,  like  these,  strong  bases. 

Monomethyl  arsine,  AsH2(CHg),  is  a  gas  which  liquefies  at  0°  and  which 
readily  oxidizes  into 

Methyl  arsine  oxide,  CH.-AsO,  or  into 

Methyl  arsenious  acid,  CH3-AsO(OH)H. 

Trimethyl  arsine,  AsCCH^)  ,  is  a  colorless  liquid  boiling  at  220  ,  and 
which  Is  obtained  by  treating  zinc  methyl  with  arsenic  trichloride: 
2AsCl,  +  SZnCCHj)^  =  3Zna2  +  2As(CH3)„  It  combines  with  oxygen,  form- 
ing trimethyl  arsine  oxide,  As(CH,).0,  with  the  halogens,  forming 
As(CHi;),Cl,,  etc.  With  methyl  iodide  it  combines  directly,  formmg 
tetramethyl  arsonium  iodide,  As(CH3)J,  which  crystallizes  m  colorless 
plates. 

Dimethyl  diarsine,  cacodyl,  (CH3)2As-As(CH3)2,  is  a  colorless  liquid 
boiling  at  170°,  and  with  a  most  disagreeable  odor,  and  which  readily  un- 
dei^oes  spontaneous  inflammability  in  the  air. 

Dimethyl  diarsine  oxide,  cacodyl  oxide,  alkarsm,  (CH3)jAs-0-As(CH3)-, 
is  a  colorless  liquid  boiling  at  1 50°,  and  has  a  most  nauseating  odor.  Both 
compounds  are  produced  on  distillirg  dry  acetates  with  arsenious  oxide: 


METALLIC  COMPOUNDS.  381 

4CH3COOK  +  AsjOg  =  (CH3)2As-0-As(CH3)2  +  3K2CO3+ 2CO2.     (Detection 

of  acetates  by  means  of  arsenious  oxide,  p.  363.) 

Dimethyl  arsenic  acid,  cacodylic  acid,  (CH3)2AsO(OH),  is  produced  by 

the  oxidation  of  dimethyl  diarsine  oxide.     It  occurs  as  odorless  prisms. 
Tetramethyl  arsonium  hydroxide,  As(CH3)^  OH,  and 
Tetramethyl  stibonium  hydroxide,  Sb(CH3)<'0H,  are  bodies  quite  sim^ 

ilar  in  chemical  properties  to  potassium  hydroxide. 

d.  Compounds  with  Boron  and  Silicon. 

Bormethyl,  BCCH,),,  is  a  colorless  gas  which  spontaneously  inflames 
in  the  air,  burning  with  a  greenish  flame,  and  has  an  unsupportable  sharp 
odor. 

Borethyl,  6(02115)3,13  a  colorless  liquid  which  acts  like  bormethyl 
(Preparation,  see  ^^ilicon  Ethyl.) 

Silicon  ethyl,  81(02115)4,  is  produced  from  zinc  ethyl  (p.  382)  by  the 
action  of  silicon  chloride.  It  is  a  colorless  liquid,  boiling  at  153°.  If 
this  is  treated  with  chlorine  we  obtain  monochlorsiliconethyl, 
(02H,01)-Si--(C2H5)3,  or  SiC,H,,Cl,  a  liquid  boiling  at  185°,  which,  like 
the  alkyl  chlorides,  vields  an  acetic  acid  ester  when  heated  with  alkali 
acetate:  SiC,Hj.p-f-C2H3K02  =  KCl+ (SiC8H,,)C2H302;  this  on  treating 
with  alkali  hydrate  is  converted  into  potassium  acetate  and  the  alcohol 
SiC^Hjg-OH.  According  to  this  we  must  consider  silicon  ethyl  as  nonane 
or  nonyl  hydride,  in  which  1  atom  of  carbon  is  replaced  by  eilicon.  This 
and  its  derivatives  correspond  completely  with  the  nonyl  compounds: 

Silicononane,  SiCsHjo.  '  Nonane,  ^9^20- 

Silicononyl  chloride,  SiCsH,gCl.  Nonyl  chloride,  CJi^jCl 

Silicononyl  acetate,     (SiC8Hie)C2H302.  Nonyl  acetate,    (C,H,9)C2H302. 

Silicononyl  alcohol,     SiC,H,,-OH.  Nonyl  alcohol,   C^Hi  "OH. 

12.  Metallic  Compounds, 

or  metallo-organic  combinations,  are  known  only  with  alkyl  radicals. 
Furthermore  those  metals  have  the  power  of  forming  alkyl  com- 
pounds which,  according  to  their  position  in  the  periodic  system  (p.  54), 
are  closely  related  to  the  metalloids.  As  the  basic  nature  of  the  metal 
increases,  so  does  the  stability  of  the  corresponding  alkyl  compound 
decrease  more  and  more.  The  metals  often  unite  with  a  greater 
number  of  monovalent  alcohol  radicals  than  with  monovalent  ele- 
mentary atoms;  these  compounds,  which  correspond  to  the  maxi- 
mum valence  of  the  metals,  are  volatile  liquids  which  are  generally 
converted  into  the  vaporous  form  without  decomposition.  The 
determination  of  their  vapor  density  therefore  gives  a  means  of  esti- 
mating the  valence  of  the  metals,  as  well  as  their  atomic  weight 
(p.  21). 


382  ORGANIC  CHEMISTRY. 

Preparation.  1.  By  the  direct  action  of  the  metals  or  their  sodium 
alloys  upon  the  halogen  alky  Is : 

ZnNa,  +  2C2H5I  =  Zn  (QHs)^  +  2NaI. 

2.  By  the  action  of  zinc  or  mercuric  alkyl  upon  metallic  chlorides: 

SnCl,  +  2Zn{C^R^)^=^n{QJ^^),  +  2ZnCl2. 

Properties.  Colorless  liquids,  volatile  without  decomposition,  which  in 
part  inflame  in  the  air  (magnesium,  zinc,  aluminium  alky  Is),  while  others 
(mercury,  lead,  tin  alky  Is)  are  stable. 

Zinc  ethyl,  Zn (€2115)2,  is  produced  on  heating  zinc  with  ethyl  iodide, 
whereby  zinc  ethyl  iodide  is  first  formed,  this  decomposing  into  zinc 
iodide  and  zinc  ethyl  on  further  heating: 

Zn  +  C2H5I  =  Zn/^2^6 ;    2Zn<^^2^6  =  T^niC^^^^  +  Znl^. 

Zinc  alkyls  are  decomposed  by  water  into  hydrocarbons:  Zn (€2115)2  + 
2H20=2C2H5  +  Zn(OH)2.  By  the  slow  action  of  oxygen,  zinc  alcoholates 
(p.  343)  are  produced:  Zn (62115)2  + 20  =Zn (002115)2.  On  account  of  their 
decomposability  zinc  alkyls  are  used  in  the  preparation  of  many  other 
compounds. 

Sodium  ethyl,  CgHgNa,  cannot  be  directly  prepared,  but  is  obtained  by 
the  action  of  sodium  upon  zinc  ethyl  when  the  zmc  precipitates.  A  crys- 
talline compound  consisting  of  sodium  ethyl  and  zinc  ethyl  separates  from 
the  resulting  solution  on  allowing  it  to  cool.  Pure  sodium  ethyl  cannot 
be  obtained  from  this  mixture.  All  alkali  alkyls  show  the  same  behavior, 
and  their  solutions  absorb  carbon  dioxide  with  the  formation  of  salts  of 
fatty  acids  (p.  346,  3),  and  are  decomposed  by  water  in  the  same  way  as 
zinc  alkyls. 

MONOVALENT  COMPOUNDS  OF  POLYVALENT  ALCOHOL  RADICALS. 

Polyvalent  alcohol  radicals  have  the  power,  under  certain  condi- 
tions, of  replacing  monovalent  ones  in  compounds.  The  most  im- 
portant of  these  compounds  are  derived  from  the  tri-  and  pentavalent 
alcohol  radicals  (which  see). 

COMPOUNDS  OF  THE  CYANOGEN  RADICAL. 

The  monovalent  cyanogen  radical  "CN,  is  in  many  regards  similar 
to  the  halogens;  thus  it  forms  an  acid  with  hydrogen  and  unites  with 
the  metals  and  alcohol  radicals,  forming  compounds  which  are  very 
similar  to  those  with  the  halogens.  Cyanogen  as  a  monovalent  radical 
cannot  exist  free,  but  is  doubled,  like  all  other  monovalent  radicals, 
forming  the  molecule  dicyanogen,  NC~CN.  Most  of  the  compounds 
of  cyanogen  also  form  polymeric  modifications,  which  may  be  con- 
sidered as  derivatives  of  triazine,  C3H3N3  (which  see). 

Potassium  ferrocyanide  and  potassium  cyanide  form  the  starting- 
point  in  the  preparation  of  the  cyanogen  compounds. 


COMPOUNDS  OF  THE  CYANOGEN  RADICAL,         383 

According  to  theory,  two  cyanogen  radicals  are  possible  according  as 
the  nitrogen  is  a  trivalent  element,  the  so-called  nitrile  group,  N^C~, 
or  as  a  pentavalent  element,  the  so-called  isonitril  group,  C^N", 
so  that  the  elements  or  groups  combined  with  the  cyanogen  radicals 
are  united  to  nitrogen  or  to  carbon.  According  to  another  conception 
the  carbon  exists  as  a  tetravalent  element  in  the  nitriles  and  as  a 
divalent  element  in  the  isonitriles:   N    C"  or  C=N~. 

Cyanogen  and  its  compounds  with  H,  ~0H,  ~SH,  "NHj,  CI,  etc., 
react  according  to  either  one  or  the  other  formula;  still  only  one  of 
the  two  isomerides  exists  free,  as  the  other  contains  the  atoms  in 
unstable  equilibrium,  which  in  the  preparation  of  the  respective  com- 
pound is  immediately  converted  into  the  stable  form  of  the  other 
compound  (tautomerism,  p.  300).  Nevertheless  the  two  isomers  of 
such  derivatives  of  the  above-mentioned  compounds  are  known, 
which  are  produced  by  the  introduction  of  alkyls  in  place  of  hydrogen 
(p.  390). 

Dicyanogen,  cyanogen,  CjNj  or  N^C~C— N.  Occurrence.  To  a 
slight  extent  in  the  gases  of  the  blast-furnace  and  in  illuminating- 
gas. 

Formation.  By  heating  ammonium  oxalate :  (NH4)OOC~COO(NH4) 
=  C2N2+4H20.  It  is,  according  to  this,  the  nitrile  of  oxalic  acid, 
HOOC-COOH,  and  has  the  structure  N=C-C=N.  With  water  it 
is  gradually  converted  into  ammonium  oxalate,  taking  up  HJJ. 

Preparation.  By  heating  silver  or  mercuric  cyanide  (p.  386): 
Hg(CN)2  =  C2N2+Hg;  also  by  heating  a  solution  of  copper  sulphate 
with  potassium  cyanide:'  4KCN+2CuS04  =  C2N2+2CuCN+2K2S04. 
It  cannot  be  obtained  by  the  direct  union  of  carbon  and  nitrogen 
(see  Potassium  Cyanide). 

Properties.  Colorless,  irritating,  poisonous  gas  which  liquefies 
at  —12°;  it  is  inflammable,  burning  with  a  purple-red  flame  into 
carbon  dioxide  and  nitrogen.  Water  dissolves  4  volumes,  and  alcohol 
23  volumes.  Potassium  burns  in  C2N2  to  potassium  cyanide,  KCN, 
and  potassium  hydrate  absorbs  the  gas  with  the  formation  of  potas- 
sium cyanide  and  potassium  cyanate: 

2KOH+C2N2  =  KCN+NCOK+H20  (analogous  to  chlorine). 

Hydrocyanic  Acid,  Prussic  Acid,  HCN.  Occurrence  and  Formation, 
Free  in  Pangium  edule,  certain  Aracese  and  Hydrocarpus  varieties 


384  ORGANIC  CHEMISTRY. 

of  Java,  and  as  traces  in  tobacco-smoke.  It  occurs  combined  in  the 
seeds  and  often  in  other  parts  of  the  Amygdalacse,  Drupacea,  Pomacse, 
but  especially  in  the  bitter  almond  and  the  leaves  of  the  cherry-laurel, 
where  it  exists  as  the  glucoside  amygdalin  (see  Glucosides),  which  on 
standing  with  water  decomposes  through  the  presence  of  the  ferment 
emulsin,  which  also  exists  in  these  plants,  into  hydrocyanic  acid, 
sugar,  and  benzaldehyde.  The  hydrocyanic  acid  thus  obtained  is  very 
dilute  (1  part  HCN  per  1000),  and  is  called  bitter  almond  water  when 
obtained  from  bitter  almonds  by  distillation  with  water  and  some' 
little  alcohol,  whereby  the  latter  dissolves  the  benzaldehyde,  which 
distils  over. 

The  African  Lotus  arabicus  contains  the  glucoside  lotusin,  which  by  the 
ferment  lotase,  existing  in  the  same  plant,  is  split  into  hydrocyanic 
acid,  lotoflavin,  and  dextrin. 

Hydrocyanic  acid  is  readily  formed  on  heating  ammonium  formate: 
H-COO-NH4=HCN+2H20,  and  accordingly,  is  the  nitrile  of  formic 
acid  (formonitrile,  p.  368,  3).  Ammonium  formate  is  produced  on  allow- 
ing a  watery  solution  of  HCN  to  stand,  whereby  water  is  taken  up.  Prus- 
sic  acid  is  also  produced  when  the  dark  electric  discharge  is  passed  through 
a  mixture  of  acetylene  and  nitrogen,  or  by  heating  ammonia  with  chloro- 
form under  pressure:  CHCl3  +  NH3  =  HCN  +  3HCl.  According  to  this 
reaction  hydrocyanic  acid  has  the  following  structure:  N  =CH. 

Preparation.  Ordinarily  by  distilling  metallic  cyanides  with  dilute 
inorganic  acids: 

2KCN+  H2SO4  =  K2SO4+  2HCN. 

it  is  prepared  more  readily  by  distilling  potassium  ferrocyanide  and 
dilute  sulphuric  acid,  whereby  only  one-half  of  the  cyanogen  in  the 
potassium  ferrocyanide  is  obtained  as  hydrocyanic  acid  (p.  388): 

2K,(re"C6N  e)  +  3H,S04  =  K^Fe^CFeCoNe)  +  3X^80^+  6HCN. 
In  both  cases  a  dilute  watery  solution  of  HCN  is  obtained.  In  order  to 
prepare  anhydrous  hydrocyanic  acid  we  pass  the  vapors  containing 
water  over  CaClj  and  liquefy  the  gas  by  a  freezing  mixture.  Nearly 
anhydrous  hydrocyanic  acid  is  obtained  on  distilling  potassium  cyanide 
with  50  per  cent,  sulphuric  acid  (p.  386). 

Properties.  When  anhydrous  it  is  a  colorless,  extremely  poisonous, 
penetrating  liquid  having  an  odor  similar  to  bitter  almonds,  boil- 
ing at  27°  and  crystalhzing  at  -15°.  Its  vapors  when  inhaled  cause 
death. 

It  is  a  very  weak  acid,  soluble  in  water,  alcohol  and  ether,  and  burns 
with  a  violet  fiame,  its  watery  solution  quickly  changing  into  ammo- 


COMPOUNDS  OF  CYANOGEN  WITH  METALS.        385 

nium  formate  (p.  384).  The  solution  of  prussic  acid  is  rather  stable 
in  the  presence  of  very  small  amounts  of  mineral  acids.  With  nascent 
hydrogen  it  yields  methylamine:  N=CH+4H  =  H2N~CH3,  and  under 
certain  conditions  it  is  polymerized  into  colorless  crystalline  trihydro- 
cyanic  acid  (NCH)3  (see  Triazines),  which  yields  HCN  again  on  heat- 
ing. With  hydrogen  peroxide  it  yields  non-poisonous  oxamide: 
2NCH+HA  =  H2N-OC-CO-NH2   (antidote  for  HCN  poisoning). 

Detection.  The  liquid  to  be  tested  is  treated  with  caustic  alkali 
and  a  few  drops  of  a  ferrous  and  ferric  salt  solution,  then  warmed  and 
acidified.  If  hydrocyanic  acid  is  present,  then  potassium  ferrocyanide 
is  produced,  and  this  gives  a  deep-blue  precipitate  with  the  ferric  salt. 
In  the  presence  of  very  small  quantities  of  HCN  at  first  only  a  blue 
coloration  of  Prussian  blue  is  obtained  (p.  3S8).  If  the  liquid  to  be 
tested  is  evaporated  to  dryness  with  ammonium  sulphide,  ammonium 
thiocyanide  is  produced,  and  this  gives  a  blood-red  coloration  with 
FeClg  (p.  393).  The  HCN  can  be  detected  in  its  insoluble  compounds 
or  in  mixtures  by  distilling  with  dilute  sulphuric  acid,  which  sets  the 
HCN  free,  and  then  testing  as  above  mentioned. 

I.  Compounds  of  Cyanogen  with  Metals. 

a.  Simple  Metallic  Cyanides.. 

The  simple  metallic  cyanides  or  salts  of  hydrocyanic  acid  or  cya- 
nides are  obtained  by  the  action  of  hydrocyanic  acid  upon  metaUie 
oxides  or  metallic  hydroxides:  2HCN+HgO  =  Hg(CN)2+H20.  They 
are  also  obtained  if  nitrogen  and  hydrogen  are  passed  over  heated 
carbides  of  the  alkali  or  alkaline  earth  metals,  while  if  iron  is  present 
the  corresponding  ferrocyanide  combination  is  produced  (p.  387). 

The  cyanides  of  the  light  metals  are  soluble  in  water  and  are 
decomposed  by  dilute  acids  with  the  generation  of  HCN.  Even  the 
carbonic  acid  of  the  air  sets  hydrocyanic  acid  free  from  these  cyanides, 
and  this  is  the  reason  why  they  always  smell  of  hydrocyanic  acid; 
on  the  contrary,  they  are  very  stable  even  at  red  heat.  Heated  with 
concentrated  sulphuric  acid  they  develop  carbon  monoxide:  2KCN  + 
2H2O+  2H2SO4  =  K2SO4+  (NHJ2SO4+  2C0.  The  soluble  cyanides  are 
violent  poisons. 

The  cyanides  of  the  heavy  metals  are,  with  the  exception  of  mercuric 
cyanide,  insoluble  in  water,  and  are  only  decomposed  by  strong  acids  and 
decompose  generally  into  cyanogen  and  metal  on  heating  them  to  redness. 


386  ORGANIC  CHEMISTRY, 

They  are  best  obtained  by  treating  soluble  metallic  salts  with  potassium 
c-anide:  AgN03  +  KCN  =  KN03+AgCN. 

Potassium  Cyanide,  KCN.  Preparation.  If  nitrogen  is  passed 
over  a  red-hot  mixture  of  carbon  and  potassium  carbonate,  potassium 
cyanide  is  formed:  K2C03+2N+4C  =  2KCN-f-3CO.  It  is  prepared 
on  a  large  scale,  according  to  the  same  principle,  by  heating  nitrog- 
genous  organic  refuse  (blood,  leather,  hoofs,  horns)  with  potassium 
carbonate  (see  Potassium  Ferrocyanide).  At  the  present  time  it  is 
prepared  by  heating  potassium  carbonate  with  carbon  in  ammonia 
gas,  K2C03+C+2NH3  =  2KCN+3H20,  or  by  fusing  potassium  ferro- 
cyanide: K,FeCeNe  =  4KCN+FeC2+2N.  The  finely  divided  iron 
carbide  is  separated  by  filtering  the  fused  mass  through  earthenware. 
In  regard  to  its  formation  from  chloroform  see  p.  347. 

Properties.  Colorless,  very  poisonous  cubes,  soluble  in  water 
with  alkaline  reaction  (hydrolytic  dissociation,  p.  86)  and  also  in  dilute 
alcohol.  On  heating  it  fuses  without  decomposition  and  is  an  impor- 
tant reducing  agent  because  it  unites  directly  with  oxygen  and  also 
with  sulphur.  The  watery  solution  soon  turns  brown,  undergoing 
decomposition,  whereby  potassium  formate  and  ammonia  are  pro- 
duced: KCN+2H20==CHK02+NH3.  Potassium  cyanide  precipi- 
tates the  corresponding  metaUic  cyanide  from  solutions  of  the  heavy 
metals,  these  being  soluble  in  an  excess  of  the  potassium  cyanide 
(see  below).  Its  aqueous  solution  dissolves  finely  divided  gold,  hence 
it  is  used  for  the  extraction  of  the  latter  (which  see). 

Silver  cyanide,  AgCN  (or  AgNC,  p.  391,  2),  is  precipitated  as  a  white 
cheesy  precipitate  from  silver  salts  by  potassium  cyanide.  It  is  similar 
to  silver  chloride,  but  does  not  darken  when  exposed  to  the  light. 

Mercury  cyanide,  mercuric  cyanide,  Hg(CN)2,  is  obtained  by  dissolv- 
ing mercuric  oxide  in  hydrocyanic  acid  and  evaporating.  It  consists  of 
colorless  crystals  which  are  soluble  in  water  and  alcohol.  It  can  also  be 
obtained  from  Prussian  blue  (p.  388). 

h.  Conipound  Metallic  Cyanide. 
The  cyanides  of  the  heavy  metals  which  are  insoluble  in  water 
are  soluble  in  a  watery  solution  of  potassium  cyanide  with  the  forma- 
tion of  crystallizable  compounds  soluble  in  water;  for  example,  AgCN+ 
KCN  =  KAg(CN)2.  As  these  compounds  do  not  respond  to  the  reac- 
tions which  the  ions  of  the  salts  from  which  they  are  formed  give, 
they  cannot  be  considered  as  double  salts  but  rather  as  complex  salts 
which  contain  a  complex  anion;  for  example,  Ag(CN)2  (p.  83).     They 


COMPOUNDS  OF  CYANOGEN  WITH  METALS,        387 

may  be  divided  into  two  groups,  the  salts  of  one  group  being  poi- 
sonous and  readily  split  in  the  cold  by  inorganic  acids  with  tbf 
separation  of  simple  metallic  cyanides  and  formation  of  hydrocyanic 
acid,  KAg(CN)2+HCl  =  KCl+HCN+AgCN,  while  the  salts  of  the 
other  group  are  non-poisonous  and  spht  off  in  the  cold  with  dilute 
acids,  peculiar  complex  acids,  so  that  the  compound  must  be  con- 
sidered as  salts  of  these  acids.  To  this  group  belong  the  compounds 
of  ferrous  and  ferric,  manganous  and  manganic,  cobaltic,  chromic, 
and  platino  cyanides,  with  the  alkali  cyanides;  thus  Fe(CN)2+  4KCN  = 
K4Fe(CN)8,  with  the  anion  FeCeNe,  which  decomposes  with  acids  as 
follows: 

K^FeC^Ne  +  4HCi  =  H4FeC6N6  +  4KC1. 

Potassium  ferrocyanide.  Hydroferrocyanic  acid. 

K^PtC.N,   +  2HCl  =  H2PtC,N,  +  2KC1. 

Potassium  platinocyanide.  Hydroplatinocyanic  acid. 

KjCoCeNe   +  SHCl^HjCoCeNe  +  3KC1. 

Potassium  cobalticyanide.  Hydrocobalticyanic  acid. 

In  these  acids  the  hydrogen  is  not  only  replaceable  by  alkali 
metals,  but  also  by  other  metals.  The  salts  of  hydroplatinocyanic 
acid  have  beautiful  colors.  Barium  platinocyanide,  BaPtC4N4,  is  used 
in  the  detection  of  Rontgen  rays. 

Hydroferrocyanic  Acid,  H4Fe"C8N'6.  (In  six  condensed  hydro- 
cyanic acid  molecules  we  have  two  hydrogen  atoms  replaced  by  a 
ferrous  iron  atom.)  If  an  inorganic  acid  is  added  to  a  cold  concen- 
trated watery  solution  of  potassium  ferrocyanide,  H4Fe"C6N6  sepa- 
rates out  as  a  white  crystalline  powder. 

Of  the  salts  of  this  acid,  the  ferrocyanides,  the  potassium  salt,  the 
ferric  and  the  cupric  salts  are  of  importance,  as  it  is  in  this  form  that 
the  ferric  and  cupric  compounds  are  detected. 

Potassium  Ferrocyanide,  Yellow  Prussiate,  K^FeCsNe-  Prepara- 
tion. If  a  ferrous  salt  solution  is  treated  with  potassium  cyanide, 
a  precipitate  is  obtained  of  ferrocyanide,  Fe(CN)2,  which  dissolves  in 
an  excess  of  potassium  cyanide,  producing  potassium  ferrocyanide: 

Fe(CN),+  4KCN  =  K4FeCeN6. 

Powdered  iron  or  ferrous  sulphide  also  dissolves  when  treated  with 
a  wat*^ry  solution  of  potassium  cyanide.  Oxygen  is  taken  up  from  the 
air: 

Fe+  6KCN+  H,0+  0  =  K.FeC,Ne+  2K0H. 


388  ORGANIC  CHEMISTRY, 

Potassium  ferrocyanide  was  formerly  prepared  on  a  large  scale  by 
heating  carbonized  nitrogenous  refuse  with  potassium  carbonate 
and  iron.  The  carbon  and  nitrogen  united  with  the  potash,  forming 
potassium  cyanide  (p.  386),  while  the  sulphur  contained  in  the  sub- 
stances combined  with  the  iron,  forming  iron  sulphide.  If  the  fused 
mass  was  treated  with  water,  the  following  transformation  took  place: 
FeS+  6KCN  =  K,FeCeNe+  K^S. 

In  Germany  at  the  present  time  nearly  all  the  potassium  ferro- 
cyanide is  prepared  from  the  iron  used  in  the  purification  of  illumi- 
nating-gas. This  contains  considerable  sulphur  besides  ferric  hydrate, 
as  well  as  the  greater  part  of  the  cyanogen  produced  in  the  distilla- 
tion of  the  coal,  in  the  form  of  iron  cyanogen  compounds  (Prussian 
blue)  and  as  sulphocyanides. 

In  order  to  purify  illuminating-gas  from  its  impurities  (HgS,  CS,,  CO,, 
NH3,  cyanogen  compounds),  it  is  not  sufficient  to  wash  the  gas  with  water, 
but  the  gas  is  passed  over  ferric  hydroxide.     The  mass  is  freed  from 


ammonium  carbonate  and  sulphocyanate  by  lixiviation  and  then  heated 

P'^oducing  calci 
water  and  treated  with  K2CO3,  which  yields  potassium  ferrocyanide.     The 


with  Ca(OH2)2,   producing  calcium  ferrocyanide,   which  is  dissolved  in 


residue  yields  SOj  on  burning  in  the  air,  and  is  used  in  the  manufacture  of 
sulphuric  acid. 

Properties.  It  forms  large  yellow  prisms  containing  3  molecules 
of  water.  It  is  soluble  in  water,  and  decomposes  on  heating  into 
nitrogen,  potassium  cyanide,  and  iron  carbide  (p.  386).  If  heated  with 
dilute  sulphuric  acid,  it  yields  hydrocyanic  acid  (process,  p.  384),  and 
with   concentrated   sulphuric   acid   carbon   monoxide   is    produced: 

K,Fe^'CeNe+  6H,S0,+  eH^O  =  FeS04+  2K2SO4-I-  6C0+ 3(NH4)2S04. 
Nitric  acid  converts  it  into  potassium  nitroprusside  (p.  389): 
K,Fe"CeN«+  3HNO3 '  KjFe"(NO')C5N5+ 2KNO3+  CO^-f-  NH,. 

Ferri -ferrocyanide,  Prussian  blue,  Fe4'"(Fe"C6N6)3,  serves  in  the 
detection  of  ferric  salts  as  their  solutions  if  treated  with  potassium 
ferrocyanide,  give  a  dark  blue  precipitate  having  the  above  constitution : 

3K4Fe"C6Ne+  4Fe'"Cl3  =  Fe/"(Fe"C«Nc)3-f  12KCI. 

It  is  decomposed  ir.bo  potassium  ferrocyanide  and  ferric  hydrate 
by  alkali  hydroxides.     On  boiling  with  freshly  precipitated  mercuric 
oxide  it  decomposes  into  mercuric  cyanide,  ferrous  and  ferric  hydrox- 
ide: 
Fe/"(Fe"C6N6),  +  9HgO+  9H,0  =  9Hg(CN),-f  4Fe(0H),+  3Fe(OH)3. 


COMPOUNDS  OF  CYANOGEN  WITH  METALS.        389 

Potassium  ferri-ferrocyanide,  KFe'^CFe^'CeNg).  Soluble  Prussian  blue. 
If  a  ferric  salt  solution  is  added  to  an  excess  of  potassium  ferrocyanide 
solution,  a  deep-blue  precipitate  is  obtained  which  is  soluble  in  water  as 
soon  as  the  potassium  salt  mixed  with  it  is  removed  by  washing. 

Potassium  ferro-ferrocyanide,  K2Fe^'(Fe^'C6N6),  is  obtained  in  the  prep- 
aration of  hydrocyanic  acid  from  potassium  ferrocyanide  as  a  white 
insoluble  powder. 

Ferro-ferrocyanide,  Fe/'CFe'^CeNe),  is  obtained  as  a  white  precipitate, 
which  quickly  turns  into  Prussian  blue  when  exposed  to  the  air  on  treat- 
ing a  ferrous  salt  solution  with  potassium  ferrocyanide. 

Cupric  ferrocyanide,  Cug'^CFe'^CeNe),  is  obtained  on  mixing  a  cupric 
salt  solution  with  a  solution  of  potassium  ferrocyanide  as  a  reddish-brown 
precipitate  which  is  insoluble  in  dilute  acids  (Hatchett's  brown). 

Hydroferricyanic  Acid,  HaFe'^CgNe.  (Six  condensed  hydro- 
cyanic acid  molecules  in  which  three  hydrogen  atoms  are  replaced 
by  one  ferric  iron  atom.)  It  is  precipitated  as  brownish  crystals 
from  a  cold  concentrated  solution  of  potassium  ferricyanide  by  treat- 
ing this  with  an  inorganic  acid. 

Of  its  salts,  the  ferricyanides,  after  the  potassium  salt,  the  ferrous 
salt  is  of  importance,  as  it  is  used  in  the  detection  of  ferrous  salts. 

Potassium  ferricyanide,  red  prussiate,  KgFeCeNg,  is  produced  on 
passing  chlorine  into  a  watery  potassium  ferrocyanide  solution: 

K4FeCeNe+  CI  =  K3Fe06Ne+  KCl. 

It  crystallizes  in  deep-red  anhydrous  prisms,  has  an  oxidizing 
action  in  the  presence  of  free  alkali,  and  evolves  oxygen  with  barium 
peroxide  in  the  presence  of  water  and  forms  barium-potassium- 
ferrocyanide: 

BaO^-F  2K3Fe'"CeNe  =  BaKe(Fe"CeN ,),-{-  O,. 

Ferro-ferricyanide,  Turnbull's  blue,  Fe3"(Fe'"C«N6)2,  serves  in 
detecting  ferrous  salts,  as  it  is  formed  on  treating  a  ferrous  salt  solu- 
tion with  potassium  ferricyanide.     It  is  a  deep-blue  precipitate: 

2K3Fe'"(CeN«)  +  3Fe"Cl,  =  Fe3"(Fe'"C..N«)3+  6KC1. 

Pot.  ferricyanide.  Turnbull's  blue. 

With  alkali  hydroxides  it  is  decomposed  into  potassium  ferricyanide 
and  ferrous  hydroxide.  The  first  quickly  changes  into  potassium  ferro- 
cyanide, and  the  ferrous  hydroxide  is  oxidized  to  ferric  hydroxide. 

c.  Nitro-priLSside  Compounds. 

These  are  formed  by  the  action  of  nitric  acid  upon  ferrocyanide  com- 
binations (process,  p.  388)  and  are  derived  from 

Hydronitropnissic  acid,  H2Fe"(NO')C5Nfi,  which  is  obtained  as  dark- 
red  prisms  on  treating  a  nitroprusside  salt  with  hydrochloric  acid.     Ail 


390  ORGANIC  CHEMISTRY. 

soluble  nitroprusside  compounds  are  colored  a  beautiful  violet  by  even 
the  most  dilute  solutions  of  metallic  sulphides  (detection  of  soluble  metallic 
sulphides). 

2.  Compounds  of  Cyanogen  with  Alkyls. 
The  hydrogen  of  hydrocyanic  acid  can  be  replaced  by  alcohol 
radicals  just  as  with  metals.  We  have  seen,  p.  383,  that  two  series  of 
isomeric  compounds  can  be  derived  from  cyanogen,  although  these 
are  not  known  in  cnnection  with  hydrocyanic  acid  and  the  metallic 
cyanides.  Both  series  are  known  with  the  cyanides  of  the  alcohol 
radicals,  and  we  differentiate  between  nitriles  and  carbylamines,  or 
isonitriles.  They  are  not  esters,  as  they  are  not,  like  these,  trans- 
formed by  bases  into  the  corresponding  alcohol  and  acid. 

a.  Nitriles. 

Properties.     In  the  nitriles  the  nitrogen  exists  as  a  trivalent  atom, 

so  that  the  alkyl  is  united  to  the  still  free  fourth  valence  of  carbon: 

N-C~CH3.     Nitriles  have  an  ethereal  odor  and  are  colorless  neutral 

liquids  or  solids  and  less  poisonous  than  the  isonitriles.     The  nitriles 

poor  in  carbon  are  soluble  in  water. 

On  heating  above  100°  with  water  or  with  acids  and  alkalies  (p.  346,  2) 
the  C  atom  of  the  cyanogen  is  converted  into  the  carboxyl  group  and 
remains  combined  with  the  alkyl,  while  the  nitrogen  is  split  ofif  as  ammonia: 

CHgC^N  +  2H2O  =  CH3-COOH  +  NH3. 

With  nascent  hydrogen  they  are  converted  into  amines: 

N=C-CH3+4H=H2N-CH2-CH3. 

This  transformation  shows  the  union  of  the  alcohol  radicals  to  the  carbon 
of  the  cyanogen. 

Preparation.  1.  By  the  dry  distillation  of  ammonium  salts  or  the 
amides  of  the  fatty  acids  with  dehydrating  agents  (phosphoric  anhy- 
dride) : 

CH3-COO-NH,  =  CHg-C^  N  +  2H2O; 
CH3-CO-NH2    =CH3-C  =  N+HA 
2.  By  heating  potassium  cyanide  with  alkyl  iodides: 
CNK  +  CH3l=CH3-C  =  N  +  KL 

(According  to  this  reaction  potassium  cyanide  contains  the  "CN  group.) 

Acetonitrile,  methyl  cyanide,  NC-CHg,  found  in  coal-tar,  is  a  pleas- 
ant-smelling colorless?  liquid. 

Fulminic  acid,  C2H2N,02'  perhaps  NC-(CH2)(N02),  nitroacetonitrile, 
is  not  known  free.     Compounds  are: 

Silver  fulminate,  NC-CAg2(N02),  which  forms  white  needles,  ex- 
ploding  with  great  violence  by  heating  or  concussion,  and  often  spon- 
taneously.    It  is  used  in  the  manufacture  of  explosives. 


COMPOUNDS  OF  CYANOGEN  WITH  HALOGENS.      391 

Mercury  fulminate,  mercuric  acetonitrile,  NC~CIIg(N02),  explodes 
with  less  violence  and  is  used  in  the  percussion  cap. 

Both  compounds  are  obtained  as  colorless  crystals  if  a  solution  of  the- 
respective  metal  in  nitric  acid  is  gradually  treated  with  an  excess  of  alcohol. 
They  decompose  into  hydroxylamin  and  formic  acid  with  HCl: 

CjHgN  A  +  2HC1  +  4H2O = HgCl^  +  2CH  A  +  2NH2(OH) . 

b.  Carbylamine  or  Isonitrile. 

Properties.  In  the  isonitriles  the  nitrogen  exists  as  a  pentavalent  ele- 
ment (p.  383),  so  that  the  alkyls  are  united  to  the  still  free  fifth  valence 
of  nitrogen:  C=N-CH3.  Isonitriles  are  very  poisonous,  disagreeable-smell- 
ing, colorless  liquids,  either  insoluble  or  difficultly  soluble  in  water. 

On  heating  with  water  to  180°,  also  by  dilute  acids  even  in  the  cold,  but 
not  by  bases,  they  are  split  into  formic  acid  and  amines,  at  the  same  time 
taking  up  water.  From  this  it  follows  that  the  alcohol  radical  is  united 
to  the  nitrogen  of  the  cyanogen: 

CH3-N  =C  +  2H2O = CH3-NH2  +  CH2O2. 

Preparation.  1.  By  warming  chloroform  and  primary  amine  bases 
with  alcoholic  potash  solution:  CH3-NH2-f  CHCl3=CH3-N=C  +  3HCl. 
(Hofmann's  carbylamine  test  for  primary  amines;  secondary  and  tertiary 
amines  do  not  give  isonitrile,  and  hence  not  the  characteristic  disagree- 
able odor.) 

2.  By  the  action  of  alkyl  iodides  upon  silver  cyanide: 

CH3I + AgNC = CH3-N=C + Agl. 
(According  to  this  reaction  silver  cyanide  contains  the  N=C  group.) 

3.  Compounds  of  Cyanogen  with  Halogens,  etc. 

The  hydrogen  of  hydrocyanic  acid  is  not  only  replaced  by  metals  and 
alcohol  radicals,  but  also  by  halogens  and  monovalent  atomic  groups: 
-OH,  -SH,  -NHg. 

a.  Chlorides  and  Amides. 

Cyanogen  chloride,  chlorcyan,  NC-Cl,  is  obtained  by  passing  chlorine 
through  a  solution  of  mercuric  cyanide  or  a  watery  solution  of  hydro- 
cyanic acid: 

Hg(CN)2  +  4C1=  HgCl^  +  2NC-C1; 
HCN  +  2C1=  HCl  +  NC-Cl. 

It  forms  an  oily  colorless  liquid  boiling  at  15°  and  whose  vapors  are  irritat- 
ing and  cause  the  flow  of  tears. 

Cyanuric  chloride,  solid  cyanogen  chloride,  N3C3CI3,  is  a  derivative  of 
triazine  (which  see),  and  is  formed  by  keeping  cyanogen  chloride,  also  by 
passing  chlorine  into  anhydrous  hydrocyanic  acid,  in  direct  sunlight.  It 
forms  shining  poisonous  crystals  which  melt  at  145°. 

Cyanamide,  NC-NH,,  is  obtained,  as  colorless  crystals  melting  at  40°  C, 
by  the  action  of  ammonia  upon  cyanogen  chloride.  If  warmed  with  dilute 
sulphuric  or  nitric  acid  it  combines  with  1  molecule  of  water  and  is  trans- 


392  ORGANIC  CHEMISTRY. 

formed  into  urea:  NC-NH2  +  H20  =  H2N-CO-NH2  (urea).  Its  watery 
solution  is  gradually  changed  into 

Dicyanamide,  (NC-NH2)2,  which  melts  at  205°  C. 

Cyanuramide,  melamine,  (NC~NH2)3,  is  obtained  on  the  polymerization 
of  cyanamide  by  heating  to  150°.C.  as  colorless  crystals  having  the  charac- 
ter of  a  monOvjasic  acid. 

b.  Compounds  of  Cyanic  Add. 

Theoretically  two  compounds  of  cyanogen  and  OH  are  possible, 
namely,  normal  cyanic  acid,  N  C~OH  (cyanogen  hydroxide),  and  isocy- 
anic  acid,  OC^NH  (carbimide).  Still  in  this  case,  like  with  hydrocyanic 
acid,  only  one  cyanic  acid  and  one  series  of  salts  (cyanates)  are  known 
which  probably  have  the  structure  NCOH,  NCOK,  etc.  Esters  of  isocyanic 
acid,  the  carbonimides,  are  known,  OC^N-CHg,  methyl  carbonimide,  as 
well  as  isocyanuric  acid,  (OCNH)^,  and  cyanuric  acid,  (NCOH) 3. 

Cyanic  acid,  NCOH,  cannot  be  isolated  from  its  salts,  as  it  decom- 
poses on  being  set  free,  NCOH  +  H20=COa4-NH3,  or  it  forms  cyan- 
uric  acid.  It  is  obtained  on  heating  cyanuric  acid,  (NCOH),,  as  a 
volatile,  irritating  liquid,  which  is  stable  only  under  0°  C.  As  soon  as  it 
is  removed  from  the  cooling  mixture  which  is  used  in  liquefying  it,  it 
passes  into  cyanelide,  (NCOH)  4,  which  is  a  white  amorphous  solid. 

Potassium  cyanate,  NCOK,  is  the  substance  from  which  all  the 
other  cyanates  are  prepared  and  which  are  obtained  therefrom  by 
double  decomposition.  It  is  produced  on  heating  potassium  cyanide 
with  readily  reducible  metallic  oxides.  It  is  ordinarily  prepared 
by  fusing  potassium  cyanide  with  red  lead  (see  Urea).  It  is  a 
white  solid,  crystallizing  in  plates,  which  are  readily  soluble  and 
which  are  only  slightly  poisonous.  Its  watery  solution  quickly 
decomposes : 

NCOK+  2H2O  =  KHCO3+  NH3. 

Amitioniuin  cyanate,  NC0(NH4),  is  obtained  by  the  action  of 
cyanic  acid  vapors  upon  dry  ammonia  gas  as  a  white  crystalline  powder 
(see  Urea).  On  the  evaporation  of  its  watery  solution  it  is  converted 
into  its  isomer  urea:  NC0(NH4)  =CO(NH2)2. 

Cyanuric  acid,  N3C3O3H3,  is  a  derivative  of  triazine  (which  see)  and 
hence  has  the  preceding  formula.  It  is  produced  by  the  action  of  water 
upon  cyanuric  chloride:  N.CaClg-f 3HOH=N3C303H3  +  3HCl.  If  acetic 
acid  is  added  to  a  solution  of  potassium  cyanate,  primary  potassium  cyan- 
urate,  N3C:P.jH2K,  gradually  separates  out  and  from  this  cyanuric  acid 
can  be  obtained  by  mineral  acids.  Cyanuric  acid  forms,  with  the 
addition  of  2  molecules  of  water,  large  colorless  crystals  which  decompose 
into  cyanic  acid  on  heating.  Only  one  cyanuric  acid  and  one  series  of 
salts  are  known,  although  the  esters  of  cyanuric  acid  and  isocyanuric 
acid  are  known  (see  above). 


COMPOUNDS  OF  CYANOGEN  WITH  HALOGENS.      393 

c.  Compounds  of  Thiocyanic  Acid. 

According  to  theory,  thiocyanic  acid,  N=C~SH,  and  isothiocyanic 
acid  or  sulphcarbimide,  SC=NH,  are  possible,  although  only  one  acid, 
NC~SH,  and  one  series  of  salts  are  known.  Still  we  know  of  esters  of 
thiocyanic  acid  as  well  as  isothiocyanic  acid.  These  last  are  also  called 
"mustard  oils,''  from  the  most  important  members  of  the  group. 

Thiocyanic  acid,  sulphocyanic  acid,  NC~SH,  is  found  in  the  gastric 
juice  of  the  dog.  It  is  obtained  as  a  colorless  irritating  liquid  by  the 
decomposition  of  mercuric  thiocyanate  with  sulphuretted  hydrogen: 
(NCS)2Hg+  H2S  =  2NCSH+  HgS.  When  anhydrous  it  is  changed  into 
yellow,  amorphous  thiocyanuric  acid,  (NCSHjg,  at  ordinary  temper- 
atures. 

On  heating  the  thiocyanates  with  dilute  sulphuric  acid,  avoiding 
an  excess  of  the  acid,  we  obtain  a  watery  distillate  of  thiocyanic 
acid.  With  an  excess  of  concentrated  sulphuric  acid  the  free  thio- 
cyanic acid  is  decomposed  into  carbon  oxysulphide  and  ammonia: 

NCSH+H20=COS+NH3. 

Sulphocyanic  acid  and  its  soluble  salts  color  even  very  dilute 
solutions  of  ferric  salts  red  with  the  formation  of  ferri- thiocyanate, 
(NCS)3Fe. 

Potassium  thiocyanate,  potassium  sulphocyanide,  NCSK,  is 
obtained  by  fusing  sulphur  with  potassium  cyanide.  It  forms  color- 
less prisms  which  are  soluble  in  water  and  alcohol. 

Sodium  thiocyanate,  sodium  sulphocyanide,  NCSNa,  occurs  in  the 
saliva  and  urine  of  man  and  other  animals. 

Ammonium  thiocyanate,  ammonium  sulphocyanide,  NCS(NH4),  is 
obtained  on  warming  hydrocyanic  acid  with  yellow  ammonium  sulphide 
or  carbon  disulphide  with  alcoholic  ammonia:  CS2  +  4NH3=NCS(NH4) 
+  (NH4)2S.  It  is  prepared  commercially  by  lixiviating  the  iron  hydrate 
used  in  purifying  illuminating-gas  (p.  388).  It  forms  colorless  prisms, 
which  are  converted  into  its  isomer  sulphur  urea  by  heating  to  170°: 
NCS{'NH,)  =  CS(NH2)2. 

Mercuric  thiocyanate,  mercury  sulphocyanide,  (NCS)2Hg,  is  obtained 
bv  precipitating  KCNS  with  a  mercuric  salt.  It  is  a  white  amorphous 
powder  which  increases  greatly  in  volume  on  burning  (chief  constituent 
of  the  so-called  Pharaoh's  serpent). 


I 


394  ORGANIC  CHEMISTRY, 


COMPOUNDS  OF  DIVALENT  ALCOHOL  RADICALS. 
I.  Divalent  Alcohol  Radicals. 

Alkylenes,  Alkenes,  or  Olefines. 

General  formula  CnH2N. 

Boiling-point.  Boiling-point. 

Ethylene     C^R^      Gas  Octylene      CaHig  125° 

Propylene  CgHe      Gas  Diamylene  CjoHao  160° 

Butylene     C.Hg     +  3°  Cetene         CuHaj  275° 

Pentylene    CgHio        39°  Cerotene      C27H5,  Solid 

Hexylene     CflH,^       70°  Melene         CgoHeo  Solid 

If  two  atoms  of  hydrogen  of  the  hydrocarbons  of  the  methane 
series,  CnH2n+2,  are  substituted,  the  hydrocarbon  residue  CnH2n 
acts  as  a  divalent  radical.  Although  the  hydrocarbon  residues  having 
the  formula  CnH2n+i  (the  alkyl)  do  not  exist  in  the  free  state,  those 
with  the  formula  OnH2n  (the  akylenes)  are  known  free.  They  are 
accordingly  called  ethylenes,  or  oil-forming  gases  (French  "gas  olefi- 
ant"),  or  olefines. 

Methylene,  CHj,  does  not  exist.  In  all  reactions  which  produce 
methylene  free  methylene  is  not  produced,  but  instead  its  polymers 
like  ethylene,  CjH^,  propylene,  CgHg,  etc.  In  the  alkylenes  two  of 
the  C  atoms  present  are  always  united  together  by  two  bonds: 
CH3-CH=CH2,  propylene. 

No  cases  of  isomers  are  possible  with  ethylene  and  propylene, 
while  with  butylene,  C4H8,  three  isomers  are  possible,  namely: 

CH3-CHrCH=CH,;  CH3=C<^™3.  CH3-CH=CH-CH3. 

Butylene.  Isobutylene.  Pseudobutylene. 

Five  isomers  of  CsH^o  are  possible.  The  number  of  isomers  is 
even  greater  than  with  the  paraffins. 

Properties.  The  lower  members  are  gaseous,  those  intermediate 
are  readily  volatile  Hquids,  and  the  higher  members  above  C^^Hj^  are  all 
colorless  solids.  Being  unsaturated  compounds,  they  unite  directly 
with  two  monovalent  atoms  (H,  Br,  CI,  I,  etc.)  or  atomic  groups,  when 
the  double  bonds  of  the  C  atoms  are  transformed  into  single  bonds; 
e.g., 

CH,  CH3  CH^  CH^Br. 

II        +2H=       1  II        +2Br=        I 

CH,  CH3  CH,  CH.Br. 

Ethylene.  Ethane.  Ethylene  bromide. 


DIVALENT  ALCOHOL  RADICALS,  395 

With  these  addition-products  two  isomers  having  the  formula 
C2H4X2  are  readily  possible,  namely,  XH2C-CH2X  and  HgC-CHX^. 
The  first  contain  the  group  H2C~CH2  and  are  called  ethylene  com- 
pounds, while  the  second  contain  the  group  H3C~CH  (p.  329)  and  are 
called  the  ethylidene  compounds.  This  nomenclature  is  also  used 
with  compounds  with  more  than  two  C  atoms  (see  Lactic  Acid). 

Isomers  of  the  dihydric  alcohols  of  the  ethylidene  series, 
H3C~CH(OH)2,  are  not  known,  as  bodies  with  more  than  one  HO 
group  united  to  one  C  atom  are  unstable  (p.  331). 

The  olefines  are  absorbed  by  concentrated  sulphuric  acid  with  the 
formation  of  alkyl  sulphuric  acid  esters,  when  the  acid  residue  attaches 
itself  to  the  C  atom  poorest  in  hydrogen  (see  below):  C4H8+H2S04  = 
C4H9HSO4  (butyl  sulphuric  acid) .  Polymerization  may  also  take  place 
with  sulphuric  acid  (or  with  zinc  chloride  or  boron  fluoride). 

The  olefines  unite  directly  with  HCl,  HBr,  and  HI.  In  these  cases 
we  find  also  that  the  halogen  atoms  also  attach  themselves  to  the 
C  atom  poorest  in  hydrogen,  producing  secondary  and  tertiary  com- 
pounds : 

CH3-CH2-CH=CH2+HI=CH3-CH2-CHI-CH3; 

Butylene.  Secondary  butyl  iodide. 

CH=C<CH3+HI  =  CH3-Cl/CH,. 

Isobutylene.  Tertiary  butyl  iodide. 

With  watery  hypochlorous  acid  they  form  so-called  chlorhydrines: 
CH2=CH2+C10H  =CH2C1-CH20H. 

Ethylene.  Ethylenchlorhydrine. 

The  olefines  are  readily  oxidized  into  acids  containing  less  C  by 
KMn04or  CrOg,  but  not  by  HNO3,  in  the  cold.  By  careful  oxidation 
in  the  presence  of  water  the  corresponding  alcohols  are  obtained: 
CkH2n(OH)2  (p.  400,  2). 

Occurrence.     On  the  dry  distillation  of  many  C  compounds  olefines 

are  obtained;  hence  they  exist  to  a  slight  extent  in  illuminating-gas 

and  in  the  tar  oils  from  wood,  brown,  bituminous  and  anthracite  coals. 

The  hydrocarbons  CnH2n,  isomeric  with  the   olefines  found  in  the 

Caucasian  petroleums,  belong  to  the  aromatic  compounds  (see  Naph- 

thenes). 

Preparation.  1.  On  distilling  monohydric  alcohols  with  dehydrating 
agents  such  as  sulphuric  acid,  zinc  chloride,  phosphorus  pentoxide: 


396  ORGANIC  CHEMISTRY. 

2.  By  warming  the  halogen  alkyls  with  alcoholic  caustic  potash: 

C^HgBr  +  KOH = C^H,  +  KBr  +  H^O. 

3.  On  the  electrolysis  of  the  alkali  salts  of  the  oxalic  acid  series: 

K00C-C2H,-C00K= C2H4  +  2CO2+ 2K. 

Potassium  succinate.     Ethylene. 

4.  By  the  action  of  alkali  metals  upon  the  halogen  compounds 
ONH2NX2: 

C^H^Br^  +  2Na  =  2NaBr + C^H,. 

Ethylene,  ethene,  defiant  gas,  CjH*  or  H2C'"CH2,is  produced  on 
the  dry  distillation  of  many  organic  substances  and  is  therefore  found 
in  illuminating-gas  (about  6  per  cent.).  It  is  obtained  on  distilling 
ethyl  alcohol  with  six  volumes  concentrated  sulphuric  acid  (p.  358) : 

C,H50H+  H2SO4  =  C2H4+  H2O+  H2SO4. 

It  is  a  disagreeably  smelling  gas  which  burns  with  a  luminous 
flame  and  shghtly  soluble  in  water  and  alcohol.  It  Uquefies  at  -1.1° 
and  a  pressure  of  43  atmospheres  or  at  — 103°  C. 

2.  Halogen  Compounds  of  the  Alkylenes. 

The  hydrogen  of  the  alkylenes  cannot  be  directly  substituted  by 
halogens,  as  addition  products  are  formed.  Substitution  products  are 
obtained  by  the  action  of  alcoholic  caustic  alkali  upon  the  addition 
products :    C,H,Cl2+  KOH  =  C2H3CI+  KC1+  B,0. 

Halogen  addition  products  with  ethylene  groups  (p.  395) — thus 
XH2C~CH2X — are  obtained  by  the  action  of  the  halogens  upon  the 
olefines  or  of  halogen  acids  upon  dihydric  alcohols.  Those  with 
ethylidene  groups — thus  H3C"CHX2 — are  obtained  by  the  action  of 
the  halogens  upon  the  paraffins  or  by  the  action  of  PCI5,  etc.,  upon 
the  aldehydes  or  ketones  of  the  methane  series: 

CH3-COH+ PCI5  =  CH3CHCI2+  POCI3. 

The  first  yield  acetylene  (CJi^)  by  the  energetic  action  of  alco- 
holic caustic  potash,  while  the  second  yield  acetals,  (CH3~CH(OC2H5)2). 
The  first  yield  glycols,  while  the  others  do  not  (p.  399).  The  other 
properties  of  the  halogen  alkylenes  coincide  with  the  halogen 
alkyls. 

Methylene  chloride,  CH2CI2  (p.  349),  is  a  liquid  similar  to  chloroform 
which  boils  at  41°  C.  and  is  used  as  a  narcotic. 

Methylene  iodide,  CHJa,  is  a  colorless  liquid  having  a  high  specific 
gravity  (3.3),  and  is  used  in  separating  those  constituents  of  minerals 
having  a  higher  specific  gravity  and  which  sink  to  the  bottom. 


AMINES  OF  THE  ALKYLENES.  397 

Ethylene  chloride,  C2H^C1,  or  CHaCl-CHjCl,  is  obtained  by  the 
uinon  of  equal  volumes  of  ethylene  and  chlorine,  or  by  heating  concen- 
trated hydrochloric  acid  with  glycol,  C2H4(OH)2,  to  200°  C.  It  is  a 
colorless,  heavy  liquid,  having  an  odor  and  action  siniilar  to  chloroform 
and  boiling  at  85°.  It  is  also  called  oil  of  the  Dutch  chemists,  liquor 
hoUandicus,  and  as  it  is  obtained  from  ethylene,  this  last  is  also  called 
"oil-forming  gas." 

If  an  excess  of  chlorine  is  allowed  to  act  upon  ethylene,  we  obtain 
products  which  are  isomeric  with  the  chlorinated  ethanes,  and  finally 
hexachlor  ethane,  CgCle,  is  obtained. 

If  ethylene  chloride  is  treated  with  alcoholic  caustic  potash  first  (see 
above)  one  molecule  of  HCl  is  split  off  and  we  obtain 

Chlor  ethylene,  vinyl  chloride,  CHa^CHCl,  a  gas  which  has  an  odor 
similar  to  garlic: 

C^H.Cla  +  KOH  =  CH2=CHC1  +  KCl  +  H^O. 

Ethylene  bromide,  C^H^Bt^,  is  a  colorless,  poisonous  liquid  boiling 
at  130°  C.  and  yields  acetylene,  CgHj,  with  alcoholic  caustic  potash: 

C^H.Br  +  2K0H = C2H2  +  2K  Br  +  HjO. 

Ethylidene  chloride,  CgH^Cla  or  CHg-CHClg,  is  produced  by  the  action 
of  chlorine  upon  ethane  or  by  the  distillation  of  aldehyde  with  phos- 

Chorus  pentachloride  (process,  p.  396).     It  is  a  pleasant  smelling  liquid 
oiling  at  60**. 

3.  Amines  of  the  Alkylenes. 

If  one  alkylene  is  introduced  in  the  place  of  two  H  atoms  of  one 
molecule  of  ammonia  imines  are  obtained:  C3Hf=HN,  trimethylen- 
imine;  G4H8=NH,  tetramethylenimine;  C5H,(,=NH,  pentamethylen- 
imine  or  piperidin  (which  see).  These  imines  are  not  well  known,  but 
most  of  the  alkylenes  form  primary,  secondary,  or  tertiary  diamines 
by  replacing  one,  two,  or  three  H  atoms  in  two  molecules  of  ammonia. 
The  diamines  are  obtained  as  basic,  colorless  Uquids  by  heating 
alkylene  bromides  with  ammonia* 

C2H4B2+2NH,  =  H2N-C2H,-NH2+2HBr; 

Ethylendiamine. 

2C2H4Br2+  2NH3  =  HN<^^2H4^j^jj+  4HBr; 

Diethylendiamine. 

ZC,B.,Bt,+  2NH3  =  N^c'hI^N+ 6HBr. 

Triethylendiamine. 

Ammonium  bases  are  also  known.  ChoHne,  one  of  these,  con- 
tains both  alkyl  and   alkylenes   (p,   379).      Some  of  the  diamines 


398  ORGANIC  CHEMISTRY.  , 

are  poisonous  and  are  the  mother-substance  of  most  ptomaines  and 
toxins. 

Ptomaines  {itrc5ij.a,  cadaver),  septicine,  ptomatine,  putrefaction 
bases,  is  the  name  given  to  a  number  of  basic,  nitrogenous,  organic 
compounds  which  occur  in  putrefying  animal  and  also  plant  proteid 
matter.  They  are  precipitated  from  their  solutions  by  the  same 
reagents  as  the  alkaloids  (which  see),  but  do  not  give  the  same  color 
reactiofis. 

As  certain  proteids  and  many  other  bodies  give  the  same  color 
reactions  as  the  alkaloids,  it  is  possible  that  the  reactions  may  be 
obtained  with  insufficiently  purified  ptomaines,  and  this  was  the  reason 
why  it  was  formerly  stated  that  the  ptomaines  gave  all  the  reac- 
tions of  the  alkaloids  and  why  they  were  incorrectly  called  "cadaver 
alkaloids."  The  ptomaines  are  mostly  amine  and  diamine  bases, 
while  the  alkaloids  are  mostly  pyridin  and  quinoline  bases. 

Certain  of  the  ptomaines  are  poisonous  and  are  called  toxines,  while 
others  are  not;  some  are  liquid  and  volatile,  while  others  are  non-volatile 
liquids  or  crystallizable  solids.  Amongst  these  we  must  mention  neurine, 
muscarine  (p.  380),  betaine  (p.380),  putresdne,  neuridine,  cadaverine,  saprine 
(see  below),  mydatoxine,  CeHjgNO,  mydine,  CgH^NO,  and  mydaleine,  all  pre- 
pared from  putrefying  meat;  gadinine,ivom  putrefying  fishes;  mytilotoxine, 
CjHisNOa,  from  poisonous  mussels,  the  sausage  and  cheese  poison,  etc.; 
anthracine,  irom  anthrax  bacilli;  tetanine  and  tetanotoxine,  CgH.jN,  from  the 
tetanus  bacillus;  typhotoxine,C^linN02,iTomihe  typhoid  bacillus;  saman- 
drine,  the  poison  of  the  salamander;  methylguanidine  (p.  412),  etc. 

The  basic  bodies,  similar  to  ptomaines,  which  are  regularly  produced 
as  decomposition  products  of  proteids  in  living  organisms  are  called  leuco' 
maines,  to  differentiate  them  from  the  ptomaines  produced  by  micro- 
organisms. 

Ethylen-ethenyl  diamine,  lysidin,  N/ q^HA^H,  and 

Diethylendiamine,  C^HjoNg  (structure,  p.  397)  piperazin,  arc  hetero- 
cyclic compounds  on  account  of  their  ring-shaped  constitution,  and  will 
be  treated  in  connection  with  these  bodies. 

Tetramethylendiamine,  putrescin,  H2N-C4H8-NH2,  or  C^Hj^Hj,  is 
formed  in  the  putrefaction  of  cadavers,  in  cultures  of  the  cholera  bacillus,  in 
many  pathological  processes,  as  well  as  in  the  putrefaction  of  omithin  (p. 
375).     It  is  poisonous. 

Pentamethylendiamine,  NgH-CsHio-NHg  or  CgHi^Ng,  cadaverin,  is 
obtained  from  cadavers  and  is  poisonous.  It  is  also  produced  in  the 
putrefaction  of  lysin  (p.  376). 

Neuridine  and  saprine,  CgHj^Ng,  are  isomeric  with  cadaverin,  are  both 
non-poisonous,  and  are  produced  in  the  putrefaction  of  meat. 

He xamethylentetr amine,  (CH2)6N4,  urotropin,  formin,  aminoform,  is 
obtained  by  the  action  of  formaldehyde  upon  ammonia  (p.  350),  and  forms 
colorless  crystals;  it  is  a  solvent  for  uric  acid,  hence  is  used  in  medicine. 


DIHYDRIC  ALCOHOLS.  399 

4.  Dihydric  Alcohols. 

General  formula,  CnN2n(OH)2. 

If  two  HO  groups  are  attached  to  the  alkylenes  after  the  rupture 
of  the  double  bonds  of  the  C  atom,  we  obtain  a  series  of  dihydric 
alcohols  which  are  called  glycols  on  account  of  their  sweet  taste: 
ethylene  glycol,  HO^HjC^CHj'OH  or  CjHeOj,  propylene  glycol, 
HO~CH2~CH2~CH2~OH,  etc.  As  we  have  two  replaceable  hydro- 
gen atoms  (hydroxyl  groups)  in  these  bodies,  it  is  possible  to  form  two 
mixed  ethers  of  the  same  alcohol  radical,  two  glycolates  of  the  alkali 
metals  (p.  343),  also  two  esters  of  the  same  acid,  etc.: 

Ch/OCCAO)  (,jj/0(CAO) 

^n.\OH  ^2"'\0(C,H,0) 

Glycol  monacetate.  Glycol  diacetate* 

^2^^\C1  ^2^*\C1 

Glycol  chlorhydrin.  Ethylene  chloride. 

^Ji4\oH  '"2-tl4\o(C,H5) 

Glycol  ethyl  ether.  Glycol  diethyl  ether. 

^il4\0H  ^2^4X^0^^ 

Monosodium  glycolate.  Disodium  glycolate. 

The  anhydrides  of  the  glycols  or  alkylene  oxides  correspond  to  the 
anhydrides  (ethers)  of  the  monhydric  alcohols.  As  the  glycol  mole- 
cule contains  two  hydroxyl  groups,  therefore  water  can  be  split  off 
from  one  molecule  in  the  same  way  as  from  the  dihydroxyl  com- 
pounds of  the  metals: 

Ca(0H)2  =  CaO+  H^O;         C^H.COH)^  =  C2H,0+  H^O 

Ethylene  glycol.     Ethylene  oxide. 

The  only  glycols  known  are  those  with  two  C  atoms  or  more  (p.  331). 

Occurrence.     They  are  not  found  in  nature. 

Preparation.  1.  From  the  ethylene  bromides,  by  heating  them 
with  silver  acetate  or  potassium  acetate: 

C2H,Br2+  2Ag(C2H302)  =  C2H,<^32H  A"^  ^AgBr. 


400  ORGANIC  CHEMISTRY. 

The  glycol  acetate  thus  obtained  is  decomposed,  by  boihng  with  caustic 
alkah,  into  glycol  and  alkaU  acetate: 

CA<cS8;+2KOH=C,H,<^gH^2K(C,H,0,). 

2.  By  the  oxidation  of  olefines  in  the  presence  of  water: 
C2H4+  H2O+  O  =  C^H.COH)^. 

Properties.  The  solubility  of  the  compounds  in  water  increases 
as  the  number  of  alcohohc  hydroxyl  groups  contained  in  the  com- 
pound increases,  while  the  solubility  in  alcohol  and  especially  in  ether 
diminishes.  At  the  same  time  a  marked  rise  in  the  boihng-point 
takes  place  and  the  bodies  become  sweet.  Consequently  the  glycols 
have  a  sweeter  taste,,  are  more  readily  soluble  in  water  and  only  slight- 
ly soluble  in  ether,  and  boil  at  about  100°  higher  than  do  the  corre- 
sponding monohydric  alcohols.  On  oxidation  the  primary  glycols 
yield,  besides  the  numerous  intermediary  products  (p.  402),  also 
diatomic  monobasic  acids  (oxyfatty  or  lactic  acid  series,  p.  403),  as 
well  as  diatomic,  bibasic  acids  (oxalic  acid  series,  p.  420).  The  number 
of  isomers  is  even  greater  than  in  the  monhydric  alcohols;  thus  there 
are  six  isomeric  butylene  glycols  possible. 

Besides  the  normal  or  diprimary  glycols  there  are  primary-secondary, 
primary-tertiary,  disecondary,  secondary-tertiary,  and  ditertiary  glycols 
(pinacones,  p.  372,4): 

CH^COH)  CH^COH)      CH2OH  CH3  CH3  CH3     CH3 

CH2  CH(OH)      m^  CH(OH)  CH(OH)  C(OH) 

CH2  in^              C(OH)  CH(OH)  C(OH)  C(OH) 

CH^COH)  CH3        CH3    CH3  CH3  CH3    CH3  CH3  CH3 

Diprimary.      Primary-      Primary-  Di-  Secondary-  Ditertiary. 

secondary,     tertiary.  secondary.         tertiary. 

5.  Esters  and  Ethers. 

Ethylene  chlorhydrate,  ethylene  chlorhydrin,  CjH/S    ,  is  formed  by 

the  direct  union  of  HCIO  with  ethylene  or  when  ethylene  glycol  is  warmed 
with  hydrochloric  acid: 

It  is  a  colorless  liquid. 

<01T 
OSO  -OH'  ^^  produced  on  warming  glycol 
with  sulphuric  acid. 


ESTERS  AND  ETHERS  OF  DIHYDRIC  ALCOHOLS.    401 

Ethylenhydrin-sulphuric  acid,  isathionic  acid,  oxyethyl-sulphonic  acid, 
OH 
C2H4<oQ  OH'  ^^  isomeric  with  ethjd  sulphuric  acid,  C2H6~OS02'OH,  and 

forms  deliquescent  crystals  on  heating  ethylene  chiorhydrine  with  potas- 
sium sulphite 

Sulpho-  or  sulphonic  acids  (not  to  be  mistaken  for  the  inorganic  sul- 
phonic  acids,  p.  176)  contain  the  sulphur  of  the  monovalent  group  -SO3H 
united  directly  with  the  carbon  of  the  radicals,  while  in  the  isomeric  com- 
pounds the  sulphurous  acid  unites  the  carbon  to  the  oxygen.  Perhaps 
this  can' be  explained  by  the  existence  of  two  sulphurous  acids: 

OS<^H  02S<H  os<^[?A)       o,s<^A 


OH  ^2-^  OH  ^""^OH  ^2^^  OH 

jtric  Unsymmetric  Ethyl  sulphurous  Ethyl  sul- 

Sulphurous  acia.  acid.  phonic  acid- 


Sulphinic  acids  containing  the  monovalent  group  SOjH  are  also  known; 
e.g.,  ethyl  sulphinic  acid,  CjHc-SOjH. 

.        .  NH 

Taurine,  amidoethyl-sulphonic  acid,  C2H4<oq  ?t,  exists,  combined  with 

cholic  acids,  as  taurochohc  acid  and  chenotaurocholic  acid  in  the  bile- 
acids  (p.  370)  containing  sulphur.  It  forms  colorless  neutral  prisms  which 
are  insoluble  in  alcohol  but  readily  soluble  in  water. 

Taurocholic  acid,  C26H45NO7S,  occurs  in  ox  and  human  bile  and  forms 
silky  needles  which  are  easily  soluble  and  decompose  into  taurine  and 
cholic  acid  on  boiling  with  alkalies  or  water  (p.  370) : 

C2  H,5N0;S  +  H2O  =  C2H 7NO3S  +  C24H,o05. 

Chenotaurocholic  acid,  Ca^H^gNOgS,  occurs  in  goose  bile  and  decom- 
poses into  taurine  and  chenochohc  acid  (p.  370). 

Ethylenethyl  ether,  glycolethyl  ether,  C^U,<q^^^^\ 

Ethylenediethyl  ether,  glycoldiethyl  ether,  C2H4<q>^'S6^  is  a  color- 
less liquid  boiling  at  127°. 

Metallic  sodium  dissolves  in    the   cold  in  glycol  with  the  formation  of 
sodium  glycol,  and  on  heating  it  forms  disodium  glycol,  C2H4<  qj^^.    Both 

form  colorless  crystals  which  form  the  corresponding  ether  with  the  halogen 
derivatives  of  the  alkyls: 

C2H,<^g^+  C2HJ=C2H,<gg^2H5)^  Nal. 
<^H,<gN^  +  2C2HI=C2H,<g[C.H,)^2NaI. 

Ethylidene  diethyl  ether,  acetai,  CH3-CH<q|^2H5)  (p  35^^  g^^  occurs 

as  a  product  in  the  distillation  of  brandy.  It  is  a  colorless  liquid  boiling 
at  104°  C,  and  is  produced,  with  aldehyde,  in  the  oxidation  of  alcohw 
and  also  from  sodium  ethylate  and  ethylidene  bromide: 

CH,-CH  Br2 + 2C2Hr  ONa = CH3-CH  (OC2H5)2  +  2NaBr. 


402  ORGANIC  CHEMISTRY 

Ethylene  oxide,  ethylene  ether,  CgH^O  (structure  below),  is  obtained  on 
the  distillation  of  ethylenchlorhydrine  (p.  395)  with  caustic  alkali. 

C2H,<g^g  +  KOH  =  <^^2>o  +  KCl  +  H20.     . 

It  is  a  liquid  boiling  at  14°  and  having  an  ethereal  odor  which  mixes  with 
water  and  unites  gradually  therewith,  forming  ethylene  glycol.     It  unites 
directly  with  acids,  forming  monoglycol  esters:  HO-C2H4-HSO4. 
Ethylidene  oxide,  CH3-CHO,  is  ethyl  aldehyde  (p.  359). 

6.  Derivatives  with  Aldehyde  and  Ketone  Groups. 

The  dihydric,  primary  alcohols  on  oxidation  yield  two  aldehydes 
and  two  acids,  according  to  whether  hydrogen  is  removed  and  oxygen 
introduced  in  only  one  or  both  CHj-OH  groups: 

HO-H.C-CH^OH  OHC-CH,OH  OHC-CHO 

Glycol.  Glycol  aldehyde.  Glyoxal. 

HOOC-CH^OH  HOOC-CHO  HOOC-COOH 

Glycolic  acid  (Monobasic).     Glyoxylic  acid  (Gloyxalic  acid).     Oxalic  acid  (Bibasic). 

It  follows  from  the  constitution  that  these  compounds  show  in 
part  different  functions  (p.  337).  Thus  glycolaldehyde  has  the 
properties  of  an  alcohol  on  account  of  the  CH2~0H  group  and  an 
aldehyde  because  of  the  CHO  group;  hence  it  may  be  called  an  alde- 
hyde alcohol  (aldose).  The  compounds  with  two  aldehyde  groups,  like 
glyoxal,  are  called  dialdehydes.  Glyoxylic  acid  is  an  aldehyde  acid, 
while  glycolic  acid  is  an  alcohol  acid,  etc. 

The  secondary  glycols  also  yield  mixed  compounds  on  oxidation  (p.  337) 
and  the  primary-secondary  alcohols  (p.  400)  yield  aldehyde  alcohols 
Caldoses),  ketone  alcohols  (ketoses),  ketone  aldehydes,  alcohol  acids, 
ketone  acids: 

CH3-CH .  OH-CH2OH     CH3-CO-CH2OH  CH. -CO-CHO 

a-Propylene  glycol.  Acetone  alcohol.  Methyl  glyoxal. 

CH3-CHOH-CHO  CH3-CHOH-COOH      CH3-CO-COOH 

Lactic  acid  anhydride.  Lactic  acid.  Pyroracemic  acid. 

The  disecondary  glycols  yield  ketone  alcohols  and  diketones,  but  no 
acids  (p.  334).  All  aldoses  and  ketoses  which  have  an  HO  group  attached 
to  the  C  atom  neighboring  the  aldehyde  or  ketone  group  belong  to  the 
class  of  bodies  called  sugars. 

Glycoaldehyde,  HO'HaC-CHO,  only  obtained  indirectly  and  only  in 
solution.  It  is  a  sugar-like  body  (which  see)  and  reduces  Fehling's  solu- 
tion and  combines  with  phenylhydrazin. 

Glyoxal,  OHC-CHO,  is  an  amorphous,  colorless  solid. 

Glyoxalic  acid,  OHC-COOH,  glyoxylic  acid,  occurs  in  the  leaves 
and  unripe  fruit  of  many  plants  and  as  traces  in  acetic  acid,  and  forms 


OXY FATTY  ACID  OR  LACTIC  ACID  SERIES.         403 

colorless  crystals  with  1  molcule  HgO,  which  cannot  be  removed;  hence 
the  formula  (H0)2"=HC~C00H  is  often  given  to  this  body  (see  Alcohols, 
p.   331). 

Pyroracemic  acid,  acetyl  formic  acid,  CH3-CO-COOH,  is  a  ketonic 
acid  (p.  364)  and  is  obtained  on  heating  tartaric  acid  (p.  428),  or  by  the 
oxidation  of  ethylidene  lactic  acid  (p.  406),  or  by  heating  glyceric  acid 
(p.  433).  It  is  a  liquid  having  an  odor  similar  to  acetic  acid  and  boils 
at  170°.  With  nascent  hydrogen  it  yields  ethylidene  lactic  acid,  and  on 
boiling  it  partly  decomposes  into  pyrotartaric  acid: 

2C3HA=C,H30,+CO,. 
7,  Oxy fatty  Acid  or  Lactic  Acid  Series. 

General  formula  CnH2n03. 

Carbonic  acid,     CH^Og  Oxybutyric  acids,  C^HgOg 

GlycoUic  acid,    CgH^Oa  Oxyvaleric  acids,    CgHioOg 

Lactic  acids,       C^HgOg  Oxycaproic  acids,  CeHiaOg,  etc. 

Properties.  The  dihydric,  monobasic  acids  from  the  glycols  are 
called  the  acids  of  the  lactic  acid  series,  because  of  their  most  impor- 
tant member,  or  the  oxyfatty  acids,  as  they  have  one  atom  O  more  than 
the  fatty  acids;  thus  C^H402,  acetic  acid;  C2H4O3,  glycoUic  acid.  Car- 
bonic acid,  or  oxyformic  acid,  HO~CO~OH,  which  is  not  known  free, 
because  of  its  symmetrical  structure,  shows  no  difference  between 
the  two  OH  groups  and  is  hence  bibasic  and  forms  the  connection 
between  the  above  group  of  acids  and  the  bibasic  acids  of  the  glycols 
(p.  420).     For  this  reason  it  will  be  treated  of  on  p.  408. 

The  other  acids  are  colorless  and  crystallizable,  readily  soluble  in 
water  but  less  soluble  in  ether  than  the  corresponding  fatty  acids; 
also  less  volatile,  and  cannot  be  distilled  at  ordinary  pressures  without 
decomposition.  On  oxidation  they  yield  acids  of  the  oxalic  acid 
series.  They  behave  in  regard  to  their  chemical  properties  like 
alcohols  and  acids  on  account  of  their  structure.  The  hydrogen  of  the 
carboxyl  group  can  be  readily  replaced  by  metals  or  alcohol  radicals, 
producing  normal  salts  or  esters  respectively : 

HO-H^C-COOK;    HO-H^C-COOCC^Hs). 
The  CHj^OH  group  behaves  exactly  Hke  as  in  the  alcohols,  the 
hydrogen  being  replaceable  by  alkali  metals  and  by  alcohol  or  acid 
radicals : 

CH^OH   CH^OH     CH^-OCC^Hs)    CH^-OCC^Hs) 

COOH    C00(C,H5)   COOH       COO(C2H5) 

GlycoUic  acid.     Ethyl  glycollate.     Ethyl  glycoUic  acid.     Diethyl  glycollate. 


404  ORGANIC  CHEMISTRY. 

The  number  of  isomers  is,  as  with  the  dihydric  alcohols,  much  greater 
than  with  the  monohydric  acids.  There  are  two  structural  isomers  of 
lactic  acid  possible, 

CH,-CH(OH)-COOH     and    CH2(OH)-CH2-COOH, 
Ethylidene  lactic  acid.  Ethylene  lactic  acid- 

and  five  of  oxybutyric  acid.  We  differentiate  between  the  isomers, 
according  to  whether  the  HO  group  exists  next  to  the  COOH  group  or 
whether  it  is  removed.  They  are  designated  a-,  ^-,  ;--,  etc.,  acids  (p.  329). 
The  divalent  groups  which  are  united  with  the  two  hydroxyls  are 
called  the  radicals  of  the  oxy fatty  acids.  They  are  also  designated  a, 
/?,  Y,  etc.,  according  to  the  position  where  the  hydroxyl  is  lacking: 

-OC-CHa-glycolyl,  -CH^-CHo-CO-ZJ-lactyl,  CHg-fcH-C^O  a-lactyl. 

The  formation  of  anhydrides  may  take  place  as  follows: 

o    The  internal  anhydrides  are  produced  by  the  removal  of  1  mol.  H/) 

from  the  alcoholic  hydroxyl  and   the  carboxyl  of  one  molecule  of  the 

acid. 

These  are  called  lactones,  and  are  designated  by  adding  -olid  to  the 

hydrocarbon  from  which  they  are  derived: 

^  CH2-CH2-CH2 .  c\      Buty rolactone, 
^  CO >  ^'     Butanolid. 

Contrary  to  other  acid  anhvdrides,  the  lactones  are  chemically  in- 
different. They  are  very  readily  prepared  from  the  7--oxyfatty  acids, 
which  are  mostly  known  only  as  lactones. 

By  the  removal  of  1  mol.  H^O  from  the  alcoholic  hydroxyl  and  a 
neighboring  alcohol  radical  of  /?-oxyfatty  acids  we  obtain  unsaturated  acids : 
CH-CH(OH)-CH2-COOH  (/9-oxybutyric  acid)  =  CH3-CH=CH-C00H 
(crotonic  acid)+H20. 

h.  On  the  removal  of  1  mol.  HjO  from  the  carboxyls  of  2  mol.  acid 
we  do  not  obtain  true  acid  anhydrides  (p.  336): 
^^OC-CH^OH 
^^OC-CH^OH- 

c.  The  alcoholic  anhydrides  are  formed  by  the  removal  of  HgO  from 
two  alcohol  hydroxides  of  two  acid  molecules:  HOOC-CH^-O-CHj-COOH, 
diglycolJic  acid. 

d.  By  the  removal  of  HgO  from  one  alcohol  hydroxyl  and  one  car- 
boxyl group  of  two  acid  molecules  we  obtain  acid  esters,  incorrectly 
called  acid  anhydrides,  as  the  true  acid  anhydrides  (see  above)  are  not 
known : 

COOH  CH2OH        COO CH2 

I  +1  =1  I  +H2O,     glycollic  anhydride 

CH2OH        COOH  CH2OH    COOH 

e.  By  the  removal  of  2  mol.  HgO  from  both  alcoholic  hydroxyls 
and  of  both  carboxyls  of  two  molecules  of  acid  (or  by  the  removal  of 
1  mol.  HgO  from  the  simple  esters)  neutral  double  esters  ending  in  id  are 
produced: 

COOH         CHoOH  COO CH2 

[  +    I     "        =2H20+    I  \      ,glycolid. 

CH3OH        COOH  CH2-OOC 


OXY FATTY  ACID  OR  LACTIC  ACID  SERIES.         405 

/.  Diacid  anhydrides  are  obtained  on  the  removal  of  2  mol.  HgO  in 
such  a  manner  that  1  mol.  HgO  comes  from  the  two  alcoholic  hydroxyls 
and  1  mol.  H^O  from  the  two  carboxyls: 

CH:-0H=C00H=2H.0+0<ggj:Cg>,  diglycoUic  anhydride. 

Preparation.  1.  By  the  gentle  oxidation  of  the  glycols  by  dilute 
nitric  acid  or  platinum-black. 

2.  By  the  action  of  hydrocyanic  acid  and  hydrochloric  acid  upon 
the  aldehydes  we  obtain  the  acids  containing  one  ethylidene  group. 
Oxycyanides  (p.  351,  9)  are  first  formed  and  the  cyanogen  group  is 
transformed  into  the  carboxyl  group  by  the  presence  of  the  hydro- 
chloric acid  (p.  346,  2): 

CH3-COH+  CNH  =  CHj-CHCOH)  (CN) 
CH3-CH(0H)  (CN)  +  2H2O  =  CH3-CH  (OH)  -COOH+  NH3. 

Ethylidene  lactic  acid. 

The  acids  containing  one  ethylene  group  are  also  produced  from 
the  chlorhydrins  (see  Ethylene  Lactic  Acid). 

3.  On  boiling  the  monobrom-  or  monchlorfatty  acids  with  alkali 
hydroxides : 

HOOC-CH2CI+  KOH  =  HOOC-CH2OH+  KCl. 

Monochloracetic  acid.  Oxyacetic  acid. 

The  reverse  may  take  place,  i.e.,  the  oxyfatty  acids  can  be  converted 
into  the  brominated  fatty  acids  if  they  are  heated  with  hydrobromic 
acid  exactly  the  same  as  ethyl  alcohol  'is  converted  into  ethyl  bromide 
by  hydrobromic  acid: 

HOOC-CHpH  +  HBr = HOOC-CH^Br  +  H^O. 
Glycollic  acid  Bromacetic  acid. 

If,  on  the   contrary,  we  heat  with   hydriodic  acid,  we  obtain  fatty 

acids  (p.  346,  5): 

HOOC-CH2OH  +  2HI= HOOC-CH34-H2O  +  21. 

4.  By  the  action  of  nitrous  acid  upon  the  amido-acids  (p.  369,  3): 

HOOC-CH;,(NH,)  +  HN02=  HOOC-CH,OH  +  2N  +  H^O. 

Amidoacetic  acid'.  Oxyacetic  acid 

5.  By  the  action  of  nascent  hydrogen  upon  ketonic  acids  (p.  364,  2) 
or  ketonic  acid  ester  (p.  365)  we  obtain  also  the  oxyfatty  acids  derived 
from  ethylidene.  ....      , 

Glycollic  acid,  oxyacetic  acid,  CgH^Og,  is  a  constituent  of  the  juice  from 
unripe  grapes  as  well  as  the  juice  from  Ampelopsis  hederacea.  It  forms 
colorless  crystals  which  are  soluble  in  water  and  which  yield  oxalic  acid 
on  oxidation. 


406  ORGANIC  CHEMISTRY. 

Ethylidene  Lactic  Acids,  CH3-CH(0H)-C00H,  a-oxypropionic 
acids.  Three  are  known,  one  optically  inactive,  one  dextrorotatory, 
and  one  Isevorotatory;  their  existence  is  explained  by  the  stereo- 
chemical theory  (p.  303). 

1.  Fermentation  Lactic  Acid,  Inactive  Lactic  Acid. 

Occurrence.  It  is  produced  in  a  special  fermentation  (p.  373,  2)  of 
starch,  as  well  as  of  certain  sugars,  and  therefore  occurs  in  many  sub- 
stances which  contain  starch,  sugar,  etc.,  and  which  have  become 
sour,  such  as  sour  milk,  sauerkraut,  sour  pickles,  spent  tan,  the  fer- 
mented juice  of  the  beet-root.  It  is  sometimes  found  in  the  contents 
of  the  stomach  and  intestine,  in  the  blood  taken  from  cadavers,  and 
in  the  gray  substance  of  the  brain. 

Preparation.  1.  Ordinarily  by  the  fermentation  of  certain  sugars, 
etc.,  according  to  the  method  given  on  p.  373,  2  accompanied  with 
butyric  acid.  The  calcium  lactate  formed  is  transformed  by  means 
of  zinc  chloride  into  the  readily  crystallizable  zinc  lactate,  and  this 
decomposed  by  HjS  into  zinc  sulphide,  which  can  be  filtered  off  and 
the  filtrate  evaporated  on  the  water-bath  and  then  repeatedly  dis- 
tilled in  a  vacuum. 

2.  By  the  oxidation  of  secondary  jpropylene  glycol,  CHg-CHCOH)- 
CH2OH,  as  well  as  by  the  action  of  HCl  upon  aldehyde  and  hydrocyanic 
acid  (process,  p.  405,  2). 

3.  From  pyroracemic  acid,  C3H4O3,  by  the  action  of  nascent  hydrogen: 

C3HA  +  H,=C3HA. 
Properties.  It  forms  colorless  and  odorless  crystals  which  melt  at 
18°  C.  and  which  are  soluble  in  water,  alcohol,  and  ether.  It  is  volatile 
without  decomposition  only  under  very  diminished  pressure,  and  is 
hygroscopic,  hence  it  becomes  dehquescent  on  keeping.  On  gentle 
oxidation  it  yields  pyroracemic  acid:  CH,~CH(OH)~COOH+0=- 
CHj'CO'COOH+HjO,  but  on  stronger  oxidation  acetic  acid  is  ob- 
tained : 

CH,  CH3 

I  +20=1  +CO,+  H,0. 

CH(OH)COOH  COOH 

Lactic  acid  containing  25  per  cent,  water  is  a  thick  liquid.  Its  salts 
are  called  lactates.  Zinc  lactate,  Zn(C,^H503)2,  crystallizes  with  3  mol. 
H2O,  and  calcium  lactate,  Ca(CiH503)2,  which  is  soluble  in  alcohol,  crystal- 
lizes with  5  mol.  H2O  (differing  from  the  optically  active  lactic  acids). 
Ferrous  lactate,  Fe(C3H503)2  +  3H20,  forms  greenish-white  crystalline 
crusts  which  are  soluble  in  water. 


OXYFATTY  ACID  OR  LACTIC  ACID  SERIES.         407 

Fermentation  lactic  acid  contains  one  asymmetric  C  atom,  but  is  optically- 
inactive,  as  it  consists  of  a  dextro-  and  a  Isevorotatory  modification 
(p.  306).  It  is  split  into  these  two  on  the  fractional  crystallization  of  its 
strychnine  salts,  Laevolactic  acid  is  obtained  by  the  action  of  the  Bacillus 
acidi  Isevolactici,  as  it  consumes  the  dextrolactic  acid  (p.  39).  The  fungus 
PeniciUium  glaucum  produces  dextrolactic  acid,  as  it  consumes  the  laevo- 
lactic acid.  On  mixing  the  two  active  modifications  the  inactive  lactic 
acid  is  obtained  again  (p.  39). 

2.  Sarco-  or  Paralactic  Acid,  Dextrorotatory  Lactic  Acid.  It  is  pre- 
pared as  above  described  and  is  found  in  bile  and  in  muscle  plasma  as 
alkali  salt.  After  violent  work  and  after  rigor  mortis  the  quantity 
in  the  muscles  may  increase  so  that  they  have  an  acid  reaction.  It 
is  often  found  in  the  urine  and  blood  as  a  pathological  constituent. 

3.  Lcevorotatory  Lactic  Acid.  Preparation  as  above.  Both  opti- 
cally active  modifications  coincide  with  fermentation  lactic  acid  in 
all  their  properties,  with  the  exception  that  their  zinc  salts  crystallize 
with  2  mol.  H2O  and  their  calcium  salts  with  4  mol.  HjO.  The 
latter  are  soluble  in  alcohol. 

Ethylene  lactic  acid,  /?-oxypropionic  acid,  hydracrylic  acid, 
CH2(OH)-CH2~COOH,  is  prepared  according  to  the  method  given  on 
p.  405, 2,  namely,  by  the  action  of  potassium  cyanide  and  hydrochloric  acid 
upon  ethylene  chlorhydrin: 

CH2(OH)-CH2Cl  +  KCN  =  CH.(OH)-CH2(CN  +KC1; 
CH2(OH)-CH2(CN)  +  2H^0= CH2(OH)-CH2-COOH  +  NH3. 

It  is  optically  inactive,  and  is  a  sirupy  liquid  which  splits  into  acrylic  acid 
and  water  on  heating:  C3H60j=C3H402  +  H20  (hence  its  name).  It  yields 
the  dihydric,  bibasic  malonic  acid  on  oxidation : 

CH2-CH2OH  CH2CH2OH  CHrCOOH 

^   CH2OH  COOH  COOH 

Propylene  glycol.  Ethylene  lactic  acid.  Malonic  acid. 

Its  very  readily  soluble  zinc  salt  crystallizes  with  4  mol.  HgO,  and  its 
calcium  salt,  which  is  insoluble  in  alcohol,  crystallizes  with  2  mol.  HjO. 

Amidoethylene  lactic  acid,  CH,(0H)CH(NH2)-C00H,  serin,  is  ob- 
tained on  boiling  silk  gelatine  (sericin)  with  dilute  sulphuric  acid. 

Cystin,  dithiodiamidodiethylidene  lactic  acid,  CeHigNjO.Sg  or 
CH3-CS(NH2)-COOH 

I  ,  occurs  seldom  as  vesical  and  kidney  calculi  in 

CHrCS(NH2)-C00H 

human  beings,  oftener  in  dogs.  It  also  occurs  to  a  slight  extent  in  human 
urine,  and  is  produced  on  the  cleavage  of  proteins.  It  forms  colorless 
crystals  which  are  insoluble  in  water,  alcohol,  and  ether,  but  readily 
soluble  in  ammonia  and  caustic  alkalies.  It  is  Isevorotatory  and  splits 
on  reduction  into  two  molecules  of 

Cystein,  CH3C(SH)(NH2)COOH,  which  is  insoluble  in  water  and  which 
also  occurs  as  a  cleavage  product  of  proteins. 


408  ORGANIC  CHEMISTRY, 

Oxybutyric  acids,  C^HsOg.  Of  the  five  isomers  of  this  acid  we  have 
learned  of  the  preparation  of  /?-oxybutyric  acid  in  treating  of  the  ketonic 
acids,  p.  364,  2.  This  occurs  in  a  Isevorotatory  form  in  the  urine  and  blood 
in  many  diseases. 

Leucinic  acid,  CoHigOa,  is  formed  by  the  action  of  nitrous  acid  upon 
amidocaproic  acid  (process,  p.  376). 

Lanopalmitic  acid,  CieHgjOs,  occurs  in  wool-fat. 

8.  Carbonic  Acid  and  its  Derivatives. 

Carbonic  acid,  oxyformic  acid,  CH2O3  or  HO~CO~OH  (p.  190), 

is  not  known  free,  but  only  as  derivatives.     It  is  a  weak  bibasic  acid 

which  differs  from  the  other  acids  of  this  series  on  account  of  its 

different  symmetric  structure,  and  it  forms  the  connection  between 

the  lactic  acid  series  and  the  oxalic  acid  series  (p.  420).     Its  acid 

esters  are  unstable,  while  its  neutral  esters  are  obtained  from  alkyl 

iodide  and  silver  carbonate,  e.g.,  Ag2C03+2C2H5l  =  (02115)20034- 2AgI, 

as  ethereal  liquids  which  are  insoluble  in  water. 

a.  Sulphoderivatives. 

Trisulphocarbonic  acid,  CHgSa  or  HS-CS-SH,  is  not  known  free  (p. 
192).  Its  primary  esters  are  not  known,  but  its  secondary  esters  are  pro- 
duced on  treating  potassium  sulphocarbonate  with  alkyl  iodides: 

K,CS3  +  2C2H5l=  (C,H,)2CS3  +  2KI. 
Disulphocarbonic  acids,  HjCOSg.     Two  isomers  are  possible: 

Sulphocarbonyl  q^^SH  Carbon  yl  qq^SH. 

disulphocarbonic  acid,  OH  disulphocarbonic  acid,  SH. 

The  free  acids  are  not  known,  nevertheless  the  secondary  esters  of  carbonyl- 
disulphocarbonic  acid  are  known  and  secondary  as  well  as  primary  esters 
of  sulphocarbonyl-disulphocarbonic  acid: 

HS-SC-OCC^H,)       and     (H6C2)S-CS-0(C2H5). 

Its  sodium  salt  is  obtained  by  treating  carbon  disulphide  with  caustic  soda: 

CS2  +  2NaOH=NaS-CS-ONa  -fHA 

Xanthogenic  acids  is  the  name  given  to  the  primary  esters  or  ether  acids 
of  sulphocarbonyl-disulphocarbonic  acid : 

Methyl  xanthogenic    pQ^OCHg,  Ethyl  xanthogenic     no^OCJI^. 

acid,  ^^<SH  acid,  ^^<SH 

Potassium  ethylxanthogenate,  KS-CS-OC2H5,  deposits  as  silky  yellow 
needles  by  mixing  carbon  disulp  ide  and  potassium  ethylate  (alcoholic 
caustic  potash):  CS2+02H5-OK=KS-CS-OC2H5.  On  heating  with 
dilute  sulphuric  acid  ethyl  xanthogenic  acid  separates  as  an  oily  liquid. 

Monosulphocarbonic  acids,  HgCOaS.  There  are  two  isomers  possible, 
HO-CS-OH  and  HO-OO-SH,  just  as  we  had  with  the  disulphocarbonic 
acids.     The  free  acids,  the  primary  salts  and  esters  are  not  known,  but  only 


CARBONIC  ACID  DERIVATIVES.  409 

the  secondary  salts  and  estera.     If  COS  is  passed  into  potassium  ethylate, 
we  obtain  the  potassium  salt  of  carbonylethylmonosulphocarbonic  acid : 

COS  +  C2H5-OK= KS-CO-OC2H5. 

h.  Amido-derivatives. 
Like  all  other  organic  bibasic  acids,  carbonic  acid  forms  the  same 
amides  and  imides  (p.  420) ;  for  example, 

co<^g       co<gg2        ^o<nh'        co=nh 

Carbonic  acid.         Carbamic  acid.  Carbamide.  Carbimide. 

Carbamic  Acid,  H0~C0~NH2,  is  not  known  free,  but  its  calcium 
salt  occurs  in  horses'  urine  and  in  the  urine  of  man  and  dogs  when 
large  amounts  of  calcium  salts  are  partaken  of.  Ammonium  car- 
bamate occurs  in  commercial  ammonium  carbonate  (p.  218)  and  is 
formed  by  the  union  of  dry  ammonia  with  carbon  dioxide,2NH3+  CO2  = 
NH2~CO~ONH4.  It  forms  a  white  crystalline  mass  which  in  the 
presence  of  water  is  transformed  into  ammonium  carbonate: 

H2N-CO-ONH4+  H2O  =  H,NO-CO-ONH,. 

Carbamic  acid  ethylester,  HgN-CO-OCgHg,  urethan,  forms  colorless 
crystals  which  are  readily  soluble. 

Carbamide,  urea,  CN^H^O  or  H^N-CQ-NHa. 

Occurrence.  It  is  the  chief  constituent  of  human  urine  (2-3  per 
cent.)  and  the  urine  of  mammaha,  birds,  and  amphibians.  It  oc- 
curs to  a  less  extent  in  the  blood,  liver,  kidneys,  lymph,  etc.,  and  in 
uraemia  it  occurs  to  a  very  great  extent  in  all  human  tissues  and  fluids. 

Formation.  1.  Like  all  amides,  by  heating  the  corresponding 
ammonium  salt;  e.g.,  from  ammonium  carbonate: 


CO<SSS^  =  CO<^H.+  2H20; 


also  by  heating  ammonium  carbamate: 

CO<NHjj^  =  CO<NH.+  H,0. 

In  both  cases  this  takes  place  by  heating  to  about  130°  in  sealed 
vessels. 
.    2.  From  carbonyl  chloride  and  ammonia: 

COCI2+  2NH3  =  CO(NH2)2+  2HC1. 


410  ORGANIC  CHEMISTRY. 

3.  Urea  is  also  formed  as  a  cleavage  product  of  guanine,  xanthine, 
creatine,  and  of  uric  acid. 

Preparation.  1.  On  evaporating  an  aqueous  solution  of  ammonium 
cyanate,  when  a  change  in  the  atomic  arrangement  takes  place: 
NCO(NH,)  =  NH2-CO-NH2. 
If  potassium  ferroeyanide  is  fused  with  potassium  carbonate  and 
minium  or  manganese  peroxide  gradually  added,  we  obtain  potassium 
cyanate,  which  is  dissolved  in  water  and  treated  with  ammonium  sulphate, 
forming  ammonium  cyanate.  This  is  evaporated  to  dryness,  and  we 
obtain  a  mixture  of  potassium  sulphate  and  urea,  which  last  can  be  ex- 
tracted by  alcohol: 

K.FeCeNe  +  K^COa  =6KCN  +FeC03; 
6KCN  +6Pb30,  =6NCOK  +  18PbO; 
2NC0K    +(NH,)2SO,=  K2SO,    +2NC0(NHJ. 

2.  Urine  is  evaporated  to  a  sirupy  consistency  and  then  treated 
with  nitric  acid,  when  difficultly  soluble  urea  nitrate  (p.  411)  crystallizes 
out.  This  is  treated  with  barium  carbonate,  which  forms  barium 
nitrate  and  free  urea,  and  the  latter  is  then  extracted  from  the 
evaporated  residue  by  alcohol. 

Properties.  It  forms  neutral  crystalline  needles  which  have  a  taste 
similar  to  that  of  saltpeter,  are  readily  soluble  in  water  and  alcohol, 
and  melt  at  132°  C.  On  heating  higher  it  decomposes  into  biuret, 
C2H3N5O2,  and  ammonia: 

2NHrCO-NH2  =  NH2-CO-NH-CO-NH2+  NH3; 
and  if  this  fused  mass  is  dissolved  in  water  and  treated  with  caustic 
alkaU  and  a  few  drops  dilute  copper  sulphate  solution,  we  obtain  a 
violet  coloration  (Biuret  reaction). 

On  heating  ^^dth  water  above  100°  or  by  boihng  with  acids  or 
alkahes  it  decomposes  into  carbon  dioxide  and  ammonia,  at  the  same 
time  taking  up  water: 

CO(NH2)2+  HP  =  CO2+  2NH3. 
The  same  decomposition  takes  place  quickly  in  the  urine  at  ordinary 
temperatures  by  means  of  certain  micro-organisms. 

Like  all  amides,  urea  is  decomposed  by  nitrous  acid  (p.  368, 4  and 
p.  369,  3): 

CO(NH2)24-  2HNO2  =  CO2+  3H2O+  4N. 

Urea  suffers  the  same  decomposition  by  chlorine  and  bromine  in 
the  presence  of  caustic  alkalies  (sodium  hypobromite  or  chloride  of 
lime) : 

CO(NH2)2+  3NaBrO  =  00^+  21i,0-\-  2N+  3NaBr. 


CARBONIC  ACID  DERIVATIVES.  411 

If  the  alkali  is  in  excess,  the  carbon  dioxide  is  absorbed  and  only 
nitrogen  is  evolved,  and  the  quantity  of  urea  decomposed  can  be 
calculated  from  the  volume  of  the  gas  (Knop-Hiifner  method). 

Urea  is  a  monoacid  base  which  combines  directly  with  acids, 
bases,  and  salts.  Urea  nitrate,  CO(NH2)2-HN03,  is  readily  soluble  in 
water,  but  nearly  insoluble  in  nitric  acid.  Urea  oxalate, 
(CO  •N2H4)  2 -0211204+21120,  is  very  sHghtly  soluble  in  cold  water. 
(Urea  is  qualitatively  detected  in  concentrated  aqueous  solution  by 
nitric  or  oxaHc  acid,  the  precipitates  of  both  salts  exhibiting  a 
characteristic  crystalline  form  under  the  microscope.) 

The  most  important  compound  of  urea  is  that  with  mercuric 
nitrate,  as  it  serves  in  the  quantitative  estimation  (Liebig-Pfliiger 
method). 

If  a  solution  containing  up  to  4  per  cent,  urea  be  treated  with  dilute 
mercuric  nitrate  solution,  we  obtain  the  compound  Hg(N03)2  + 
2CO(NH^)2  +  3HgO.  If  after  every  addition  of  the  mercuric  nitrate  we 
treat  a  few  drops  of  the  solution  with  a  soda  solution,  we  obtain,  as  soon 
as  all  the  urea  is  precipitated  and  the  slightest  excess  of  mercuric  nitrate 
exists,  a  red  precipitate  of  mercuric  oxide,  because  the  white  precipitate 
of  mercuric  urea  does  not  change  its  color  by  soda.  If  a  mercuric  nitrate 
solution  containing  a  known  amount  of  Hg  is  treated  with  a  urea  solution 
until  a  drop  taken  out  does  not  turn  yellowish  red  with  soda,  we  can  cal- 
culate the  quantity  of  urea  from  the  volume  of  the  mercuric  nitrate  solu- 
tion used. 

Sulphocarbamide,  thio-urea,  CS(NH2)2.  As  ammonium  cyanate  is  trans- 
formed into  its  isomer  carbamide  by  evaporation,  so  also  is  ammonium 
sulphocyanate  (p.  393)  converted  into  its  isomer  sulphocarbamide  on 
warming  to  170°  C. : 

OCN(NH,)  =  NH2-CO-NH2',        SCN(NH,)  =  NHj-CS-NH^. 

It  forms  colorless  needles  which  are  soluble  in  water  and  alcohol  and 
which,  like  urea,  combine  directly  with  acids,  forming  compound  sulpho- 
ureas,  which  can  be  prepared  from  CSg  and  primary  amines: 

CS2  +  2NH2CH3=  CS(NHCH3)2 + HjS. 

Allylsulphocarbamide,allyl  thio-urea,  thiosinamine,NH2"~CS~NH(C3H6)» 
forms  colorless  prisms  having  a  leek-like  odor,  and  is  prepared  from 
mustard-oil  by  the  action  of  ammonia. 

Quanidine,  CH5N3  or  NH2~C(NH)~NH2,  imido-carbamide,  is  de- 
rived from  urea  in  which  the  =0  is  replaced  by  the  divalent  imide 
group  ^NH. 

Guanidine  is  prepared  by  the  oxidation  of  guanine  (p.  417,  hence 


412  ORGANIC  CHEMISTRY. 

its  name).  It  may  be  synthetically  prepared  by  heating  cyanamide 
with  ammonium  chloride: 

C^^jj  +  NH.Cl  =  C(NH)<  ^g^4- HCl. 

It  forms  colorless  crystals  which  are  soluble  in  water  and  alcohol 
and  is  a  strong  base,  combining  directly  with  acids: 

(CH,N3)  •  HNO3.  (CH,N3), .  H,C03. 

Guanidine  nitrate  Guanidine  carbonate. 

Like  urea  (p.  413),  guanidine  also  forms  acid  and  alkyl  derivatives: 
C(NH)<NH-_%^>  C(NH)<NH,^H^^ 

Glycolyl  guanidine.  Methyl  guanidine. 

Methyl  guanidine,  C2H7N3  (structure  above),  belongs  to  the  ptomaines 
and  occurs  in  the  cultures  of  the  cholera  bacillus  as  well  as  in  putrefymg 
meat,  and  forms  poisonous  deliquescent  crystals. 

NfT 

Arginin,  CeHj^N^Og  or  C(NH)  <  j^ jjIq  jj  /j^ jj  \q  .  guanidme  diamido- 

valerianic  acid,  is  produced  on  the  cleavage  of  proteids  by  acids,  and  de- 
composes on  boiling  with  baryta- water  mto  urea  and  ornithm  (diamido- 
valerianic  acid). 

AT  XT 

Creatine,    C4H9N302    or    CJ(NH)<_^.^2^  w^j^  ^q^jj.,    methyl 

guanidine  acetic  acid.  Occurrence.  Chiefly  in  the  muscle  plasma  of 
vertebrate  animals  and  to  a  less  extent  in  blood,  brain,  amniotic 
fluid,  and  urine. 

Preparation.  1.  By  extracting  meat  with  cold  water,  boiling  the 
extract  in  order  to  coagulate  the  proteid,  precipitating  the  phosphates 
with  baryta-water,  and  evaporating  the.  filtrate  until  crystallization 
begins. 

2,  Creatine  can  be  prepared  artificially  by  heating  sarcosine  (methyl- 
amidoacetic  acid)  with  cyanamide: 

.NH(CH,)       ,p^N      _p,^„.^NH2 
<CH2COOH  +  '"<NH2-^^^"^^N(CH3)(CH2.COOH). 

Properties.  It  crystallizes  with  1  mol.  H2O  in  rhombic,  neutral, 
colorless  columns  which  are  soluble  in  74  parts  water  and  combine  with 
acids  and  with  salts.  On  boiling  with  baryta-water  it  decomposes  into  sar- 
cosine, C3H7NO2,  and  urea.  C,H,N302-f  H20=CO(NH2)2-f-C,H,NOj.  On 
heating  with  dilute  acids  water  is  split  off  and  creatinine  is  obtained. 

Creatinine,  C4H7N3O    or    C(NH)^^^"J^^>,   glycolylm ethyl 


CARBONIC  ACID  DERIVATIVES,  413 

guanidine.  Occurrence.  It  occurs  in  the  urine  of  man  and  other 
mammaUa  and  to  a  very  shght  extent  in  ox  blood  and  in  milk. 

Preparation.  1.  Ordinarily  prepared  by  heating  creatine  with 
dilute  mineral  acids. 

2.  From  the  mother-liquor  of  creatine  (p.  412,7). 

Properties.  Creatinine  occurs  as  colorless,  neutral  prisms,  "which  are 
soluble  in  11  parts  water;  this  solution  reduces  Fehling's  solution.  It 
combines  with  acids,  salts,  and  bases,  especially  on  warming,  and  is 
thereby  converted  into  creatine.  Its  most  important  compound  is 
(C4H7N.p)2-ZnCl2,  which  is  precipitated  from  creatinine  solutions  by 
zinc  chloride  as  a  difficultly  soluble  crystalline  powder  (estimation  in  urine). 
Traces  of  creatinine  can  be  detected  m  solution  (in  urine)  by  the  ruby-red 
coloration  produced  by  a  dilute  solution  of  sodium  nitroprusside  followed 
by  the  addition  of  caustic  alkali. 

c.  Ureides  and  Diureides. 
The  hydrogen  atoms  of  the  amido  groups  in  urea  can  be  replaced 
by  alcohol  or  acid  radicals.  The  alcohol  derivatives  are  called  com- 
pound ureas,  a  great  number  of  which  are  known — for  example, 
(CH3)HN~CO~NH(CH3) — and  behave  Uke  urea;  the  acid  derivatives 
with  one  molecule  urea  are  called  ureides  and  those  with  two 
molecules  urea,  diureides  or  purines.  Most  of  the  ureides  and  diureides 
behave  like  acids  although  no  carboxyl  group  is  present.  The  acid 
character  is  brought  about  by  the  carbonyl  groups  present,  which  so 
modify  the  basic  properties  of  the  imid  group,  NH,  that  its  hydrogen 
can  be  replaced  by  metals.  As  the  ureides  correspond  to  the  amides, 
so  also  by  the  introduction  of  acid  residues  containing  carboxyl 
groups  we  may  produce  ur-acids  corresponding  to  the  amido  acids. 

AUophanic  acid,  carboxyl  urea,  is  only  known  in  the  form  of  an  ester 
and  forms  difficultly  soluble  cyrstals: 

^^<NH-COOH- 

Biuret,  the  amide  of  allophanic  acid,  is  produced  on  heating  urea  to 
150°-170°  C,  and  forms  white  needles  which  are  readily  soluble; 

AUanturic  acid,  glyoxyl  urea,  (-CH(OH)-CO-,  glyoxyl),  is  obtained 
on  the  oxidation  of  hydantoin  and  allantoin  (p.  414).  It  is  also  prepared 
from  uroxanic  acid,  CjH^N^Og: 

/NH-CO 
C0<  I 

\NH-CH(OH). 


414  ORGANIC  CHEMISTRY. 

Hydantoin,  glycolyl  urea,  (-CO-CHj-,  glycolyl),  is  obtained  by  the 
action  of  HI  upon  allantoin  or  alloxanic  acid: 

Hydantoic  acid,  glycoluric  acid,  is  obtained  from  hydantoin  by  boiUng 
with  Ba(0H)2,  and  forms  colorless  prisms: 

^'^^NH-CHjjCOOH. 

Parabanic  acid,  oxalyl  urea,  (-CO-CO- ,  oxalyl),  is  produced  in  the 
energetic  oxidation  of  uric  acid  and  alloxan: 

^^    NH-CO^ 

Dimethylparabanic  acid,  cholestrophan,  is  prepared  synthetically  from 
parabanic  acid  or  from  theine  by  treatmg  with  HNO3: 

p^     N(CH,)-CO^ 
^'^<N(CH3)-C0^- 

Oxaluric  acid  is  obtained  by  carefully  heating  parabanic  acid  with 
dilute  alkalies  and  its  ammonium  salt  occurs  as  traces  in  urine: 

^^<NH-C0-C00H. 

Alloxan,  mesoxalyl  urea,  is  obtained  by  the  careful  oxidation  of  uric 
acid  (p.  419),  and  forms  colorless  prisms  which  color  the  skin  red: 

(.Q     NH-CO^Q 
'^^<NHCO>^^- 

Alloxanic  acid,  mesoxaluric  acid,  is  produced  by  the  action  of  dilute 
alkalies  upon  alloxan,  and  forms  white  crystals  which  are  readily  soluble : 

.NH-CO-CO 
"^NH^  COOH. 

Dialuric  acid,  tatronyl  urea,  is  prepared  from  alloxan  by  the  action 
of  nascent  hydrogen.     It  is  oxidized  in  the  air  into  alloxanthin: 

CO<NH.CO>^H(^H)- 

Barbituric  acid,  malonyl  urea,  is  produced  by  the  reduction  of  dialuric 
acid;  also  by  heating  urea  with  malonic  acid.     It  forms  colorless  prisms: 

^^^NH-C0>^^2* 

Allantoin,  C4H.N^03,  the  diureide  of  the  hydrate  of  glyoxalic  acid  (p. 
402),  is  prepared  from  uric  acid  by  oxidizing  with  KMnO^.  It  occurs  in 
the  urine  of  new- bom  infants,  of  pregnant  women,  of  calves,  m  the  allantoic 


CARBONIC  ACID  DERIVATIVES.  415 

fluid  of  cows,  in  the  horse-chestnut  and  maple,  and  forms  shining  crystals 
which  decompose  into  urea  and  allanturic  acid  (p.  413)  by  the  action  of 
alkalies- 

/NH-CH-NH  . 

C0<         I  >co. 

\nh-co-nh/ 

Alloxanthine,  CjjH^N^O,,  the  diureidd  of  tatroflylic  and  mesoxalylic 
acid  3.  It  is  produced  from  alloxan  by  reduction  with  SnClg.  Its  tetra- 
methyl  derivatiye  is  called  amalic  acid,  and  is  produced  from  cafTeine 
(p.  418)  by  the  action  of  chlorine  water: 


C0< 


NH-CO. 


P,^^NH-CO     l/^- 
Purpuric    acid,   imido   alloxanthine,  C^^H^N^OgCNH),  does  not  occur 
free;  its  ammonium  salt  is  called  murexid  and  is  used  in  the  detection 
of  uric  acid  (see  419). 

d.  Purin  Derivatives. 
Hypoxanthine,  CjH^N^O,   xanthine,  CjH^N^Og,  and  the  diureide  uric 

acid,  CgH^N^O,,  -contain  the  tetravalent  acid  radical  trioxyacryl,-OC~C=C-, 
of  the  hypothetical  trioxyacrylic  acid,  HOOC-C(OH)2=C(OH)2;  these 
bodies  and  their  methyl  and  amido  derivatives  may  be  derived  better  from 
purin,  CsH^N^,  than  from  urea.  Hypoxanthine,  xanthine,  and  their  de- 
rivatives, adenine  and  guanin,  are  also  called  xanthine  or  nuclem  bases,  as 
they  are  cleavage  products  of  the  nucleoproteids. 

16        5     7 

2  /N=CH-C-NH\  8 
Purin,  CjH.N,     or     HQ/  \\  >CH. 

3  4         9 

This  is  a  diazindiazole  (see  Heterocyclic  Compounds).  The  figures 
given  above  in  the  formula  serve  to  designate  the  constitution  of  the 
derivatives.  Purin  is  obtained  from  uric  acid  by  transforming  it  into 
trichlorpurin  (p.  419)  and  replacing  the  chlorine  of  this  by  nascent 
hydrogen.  It  forms  colorless  crystals  which  are  readily  soluble  and 
melt  at  216°,  forming  salts  with  acids  and  bases.  Chlorinated  purins 
serve  in  the  syntheses  of  its  derivatives. 

Adenine,  CjHgN^CNHg),  6-amidopurin,  occurs  in  the  nucleins,  in  the 
spleen,  pancreas,  tea,  etc.      It  forms  colorless  needles  with  3  mol.  HjO: 

/N=C(NH2)-C-NHv 

Kn — -1!^N>- 

Hypoxanthine,  sarcine,  CjH^N^O,  6-oxypurin  (see  p.  417): 
/NH-CO-C-NH\ 


416  ORGANIC  CHEMISTRY, 

Guanine,    CsHaNpCNHg),  amido   hypoxanthine,   2-amido-6-oxypuriii 
(see  p.  417): 

,  /NH_CO-C-NH. 

(H.N)6<: \\ > 


S H-N^^^^- 


Xanthine,  CgH^N^g*  2,6-dioxypurin  (see  p.  417): 

.NH-CO-C-NH. 

\nH C — N^ 

Heteroxanthine,  C5H3(CH3)N^02,  7 -methyl  xanthine,  opcurs  as  traces 
in  urine  and  is  a  white  amorphous  or  crystalUne  powder: 

.NH-C0-C;-N(CH3)s^ 
\nh C N^ 

Paraxanthine,  1,7-dimethyl  xanthine,  C5H2(CH3)2NP2»  occurs  as  traces 
in  urine,  and  forms  six-sided  colorless  crystals: 

/N(CH3)-CO-C-N(CH3)\ 

0C<       II >CH. 

\NH- C N^ 

Theophylline,  1,3-dimethyl  xanthine,  C5H2(CH3)2N402,  occurs  in  tea- 
leaves  and  forms  colorless  crystals: 

/N(CH3)-C0-C-NH\ 

0C!<  11         >CH. 

\N  (CH3) C — N^ 

Theobromine,  3,7-dimethyl  xanthine,  C5H2(CH3)2N^02  (see  p.  418) 

/NH-C0-C-N(CH3)\ 

0(Y  II >CH. 

\N(CH3)— C N^ 

Caffeine,  1,3,7-trimethyl   xanthine,  €511(0113) gN^Oj,  methyl  theobro- 
mine (p.  418): 

/N(CH3)-CO-C-N(CH3)v 

OCX  II  >CH. 

\N(CH3) C ^N^ 

Uric  acid,  2,6,8-trioxypurin,  CsH^N^Og  (see  p.  418): 

/NH-CO-C-NHv 
0C<  II  >C0. 


Camine,  1 ,3-dimethyI  uric  acid,  C5H3  CH3)2N403,  occurs  in  muscle 
sma  (hence  also  in  meat  extracts),  in  yeast,  and  the  juice  of  the^sugar- 
t.     It  forms  colorless  microscopic  crystalhne  masses. 


CARBONIC  ACID  DERIVATIVES,  417 

Hypoxanthine,  sarcine,  C5H4N4O  (structure,  p.  415).  Occurrence. 
Nearly  always  associated  with  xanthine  in  the  nucleins;  in  flesh,  espe- 
cially that  of  horses  or  oxen;  in  many  animal  tissues  and  fluids,  as,  for 
instance,  in  the  spleen,  Uver,  kidneys,  brain,  pancreas,  urine;  also  in 
many  plants,  such  as  the  pumpkin,  malt,  and  lupin  sprouts,  tea, 
sugar-beets,  young  potatoes,  etc. 

Preparation.     1.  By  the  action   of  nitrous   acid   upon   adenine: 

C5H5N5+  HNO2  =  C5H4N4O+  H2O+  N^. 

2.  Ordinarily  from  meat  extracts,  whose  aqueous  solution  is  pre- 
cipitated by  silver  nitrate  and  the  precipitate  dissolved  in  dilute 
hot  nitric  acid  and  then  allowed  to  stand,  when  hypoxanthine,  guanine, 
and  adenine  silver  separate  out,  while  xanthine  silver  remains  in 
solution. 

Properties.  White  crystalline  powder  which  is  soluble  with 
difficulty  and  which  combines  with  acids  and  bases. 

Guanine,  amidohypoxanthine,  CgHaN^OCNHg)  (p.  416),  is  found  in  the 
nucleins,  in  the  excrement  of  snails,  cephalopods,  and  spiders,  in  the  pan- 
creas, spleen,  liver,  lungs,  in  the  young  sprouts  of  various  plants,  and  to 
a  great  extent  in  guano. 

Preparation.  1.  From  Peruvian  guano  accompanied  with  uric  acid 
(see  p.  418). 

2.  From  meat  extracts  (see  Hypoxanthine). 

Properties.  It  forms  colorless  crystals  or  a  white  amorphous  powder 
which  is  insoluble  in  water,  alcohol,  or  ether,  and  which  combines  with 
acids  as  well  as  with  bases.  On  oxidation  it  decomposes  into  guanidine 
(CH5N3)  and  parabanic  acid  (oxalyl  urea,  C3H2N2O3) : 

C^HsN.O +  30 +  H20=CH,N3+C3H2NA  +  C02. 
Nitrous  acid  converts  it  into  xanthine : 

CgH^NsO  +  HN02=  C5H4N4O2  +  2N  +  H^O. 

Xanthine,  G5H4N4O2  (structure,  p.  416) .  Occurrence.  Seldom  alone, 
but  generally  associated  with  hypoxanthine  in  urinary  calculi. 

Preparation.    1.  Ordinarily  from  meat  extracts  (see  Hypoxanthine). 

2.  By  the  action  of  nitrous  acid  upon  guanine,  as  well  as  upon  uric 
acid  (p.  419). 

3.  From  uric  acid  by  reduction,  still  only  indirectly  (p.  419). 
Properties.     White  microcrystalline  powder  which  combines  with 

acids  and  alkalies  and  which  is  readily  transformed  into  theo- 
bromine and  caffeine  (which  see).  When  evaporated  with  chlorine- 
water  xanthine  gives  a  yellowish-red  residue  which  becomes  purple-red 
with  ammonia  (Weidel's  reaction). 


418  ORGANIC  CHEMISTRY. 

Theobromine,  dimethylxan thine,  C5H2(CH3)2N^02  (structure,  p.  416). 

Occurrence.     In  the  cacao-bean  and  as  traces  in  the  urine. 

Preparation.  1.  From  the  cacao-bean.  2.  From  uric  acid  ;,p.  U9). 
3.  By  precipitating  an  alkahne  xanthine  solution  by  lead  acetate  and  heat- 
ing the  precipitate  of  xanthine  lead  with  methyl  iodide: 

CAPbN.Oa  +  2CH3I  =  CsH2(CH3)2N,02  +  Pbl^. 

Properties.  White  crystalline  powder  which  dissolves  with  difficulty  in 
water  and  alcohol  and  sublimes  at  300°  C.  Theobromine  has  weak  basic 
properties  and  when  evaporated  with  chlorine-water  it  acts  like  xanthine. 
Its  salts  are  decomposed  by  water  into  the  free  acid  and  theobromine. 

Theobromine-sodium-salicylate,  CeH4(OH)-COONa  +  C7H7NaN,02,  di- 
uretin,  is  a  white  crystalline  powder. 

Caffeine,  guaranine,  theine,  trimethyl  xanthine,  CgHjoN^Og  or 
C5H(CH3)3N<02.  Occurrence.  In  coffee,  tea,  Paraguay  tea,  in  guarana 
paste,  in  the  cola-nut,  and  with  theobromine  in  certain  kinds  of  cacao. 

Preparation.  1.  From  coffee.  2.  From  uric  acid  (p.  419).  3.  If  theo- 
bromine is  dissolved  in  ammonia  and  silver  nitrate  added,  a  precipitate  of 
theobromine  silver,  C7H7AgN402,  is  obtained,  which  when  heated  with 
methyl  iodide  yields  caffeine:   C7H7AgN,02  +  CH3l  =  C7H7(CH3)N,02  + Agl. 

Properties.  It  forms  with  1  mol.  H^O  colorless,  neutral,  bitter, 
shining  needles  which  dissolve  with  difficulty  in  water  and  alcohol.  It 
begins  to  sublime  at  130°,  melts  at  230.5°,  and  behaves  like  xanthine 
when  evaporated  with  chlorine- water.  It  possesses  weak  basic  properties, 
and  its  salts,  like  those  of  theobromine,  are  readily  decomposed  by  water 
into  acid  and  base. 

Caffeine-sodium-salicylate,  C8H,oN402  +  2C6H,(OH)COONa,  forms  a 
white  crystalline  powder  which  is  soluble  in  water. 

Uric  Acid,  C5H4N4O3  (structure,  p.  416).  Occurrence.  Abundantly 
in  the  pasty  urine  of  birds  (hence  also  in  guano),  of  reptiles,  and  of 
invertebrate  animals;  also  in  the  gout  nodules  and  many  calcuH;  to 
a  less  extent  in  the  urine  of  carnivora,  and  only  as  traces  in  the 
urine  of  herbivora.     It  also  occurs  pathologically  in  the  blood. 

Preparation.  1.  Ordinarily  by  boiling  the  excrement  of  snakes 
or  guano,  which  consists  of  ammonium  and  sodium  urate,  with  caustic 
alkali  until  all  the  ammonia  has  been  driven  off.  After  filtering,  this 
solution  of  alkali  urate  is  poured  into  dilute  HCl,  when  the  uric  acid 
precipitates.  Guanine  can  be  obtained  from  the  filtrate  by  satu- 
rating it  with  NH3. 

2.  If  partially  concentrated  urine  is  treated  with  one-tenth  volume 
HCl  and  allowed  to  stand  in  a  cold  place  for  about  48  hours,  all  the 
uric  acid  will  be  precipitated  out. 

Formation.     1.  By  heating  urea  with  glycocoll  to  200°  C: 
C2H3(NH2)02  +  3CO(NH2)2= C5H,N,03  +  3NH3  +  2H2O. 

2.  By  heating  trichlorlactic  acid  amide  with  urea: 
CCl3-CH(OH)CO(NH2)  +  2C0  :NH2)2= QH.N.Oa + 3HCH-  NH3  +  H,0. 


CARBONIC  ACID  DERIVATIVES.  419 

3.  Malonyl  urea  (p.  414)  yields  the  isonitroso  compound,  violuric  acid, 
with  HNOg,  and  this  on  reduction  gives  amido-malonyl  urea,  amidobarbi- 
turic  acid,  or  uramil: 

CO<J;5^.gg>C=NOH  +  4H=H30  +  CO<^2:gg>CH-NH2. 

Violuric  acid.  Uramil 

On  fusing  uramil  with  potassium  cyanate  the  potassium  salt  of  pseudo- 
uric  acid  is  obtained,  and  this  differs  from  uric  acid  only  in  that  it  contains 
1  mol.  of  HgO  more.  This  can  be  split  off  by  heating  with  dilute  min- 
eral acids: 

NH-ro                                            /NH-CO-C-NHv 
CO<55g.g8>CH-NH-CO-NH,=CO<^^ H_^^>CO  +  H,0. 

Pseudo-uric  acid.  Uric  acid. 

Properties.  Uric  acid  forms  small  white  scales,  and  when  they 
form  slowly  whetstone-shaped  crystals  are  obtained.  It  is  without 
odor  or  taste,  nearly  insoluble  in  water,  alcohol,  ether,  and  acids. 
It  is  a  weak  bibasic  acid  and  forms  chiefly  primary  salts  called  urates, 
most  of  which  are  soluble  in  water  with  difficulty.  The  most  soluble 
of  the  uric  acid  compounds  are  the  combinations  with  piperazine, 
lithium,  and  utropin  (p.  398). 

On  heating  uric  acid  it  decomposes  into  carbon  dioxide,  ammonia,  urea, 
cyanuric  acid,  and  on  careful  oxidation  (with  cold  nitric  acid)  it  yields  urea 
and  mesoxalyl  urea  (alloxan,  p.  414) : 

C.H,NA+0  +  H,0=CO<JJg;gg>CO-f-CO<^g^. 

On  further  oxidation  (warming  with  nitric  acid)  the  alloxan  decom- 
poses into  oxalyl  urea  (parabanic  acid,  p.  414),  from  which  we  infer  that 

uric  acid  contains  the  C<j^_q>C  group.     Uric  acid  is  oxidized  into  the 

diureidallantoin  (p.  414)  by  KMnO,:  C,H,N,03  +  H20  +  0=C,HeN,03+C02, 
which  shows  that  uric  acid  contains  two  urea  residues. 

On  the  action  of  halogen  alkyls  upon  a  watery  solution  of  alkali,  urates 
we  obtain  the  alkyl  derivatives  of  uric  acid.  If  tetramethyl  uric  acid  thus 
obtained  be  treated  with  POCI3,  we  obtain  chlorcaffeine,  which  yields 
caffeine  with  nascent  hydrogen: 

3C,N,03(CH3),  +  P0Cl3=  3C,N,0,(CH3)3C1  +  PO(OCH3)3; 

and  trimethyl  uric  acid  in  the  same  manner  yields  theobromine. 

By  the  action  of  POCI3  upon  •uric  acid  we  obtain  2,6.8-trichlorpurin, 
which  with  nascent  hydrogen  is  changed  into  purin,  hence  the  purin  struc- 
ture of  uric  acid. 

The  reduction  of  uric  acid  into  xanthine  can  only  be  performed  as  fol- 
lows: Sodium  ethylate  converts  2.6.8-trichlorpurin  into  2.6-dioxyethyl- 
8-chlorpurin,  which  on  heating  with  HI  replaces  the  ethyl  groups,  and  the 
chlorine  with  hydrogen,  so  that  2.6-dioxypurin=  xanthine  is  the  result. 

Detection.  On  evaporating  uric  acid  with  nitric  acid  a  yellowish-red 
residue  is  obtained  which  turns  purple-red  on  moistening  with  ammonia, 


420  ORGANIC  CHEMISTRY. 

and  beautiful  blue  on  the  subsequent  addition  of  caustic  alkali  (murexid 
test,  p.  415). 

9.  Oxalic  Acid  Series. 

General  formula  CNHgN-gO^. 


Oxalic  acid 

C,H,0, 

Suberic  acid    CgHj.O^ 

Malonic  acid 

CaH.O, 

Azelaic  acid    C^HibO, 

Succinic  acid 

C,HeO, 

Sebacic  acid    CioH.gO^ 

Pyrotartaric  acid 

C.HA 

Brassylic  acid  CnHgoO  ^ 

Adipic  acid 

CeH.oO, 

Roccelic  acid  CnEJJ^ 

Pimelic  acid 

C^H^A 

etc. 

Properties.  The  dihydric,  bibasic  acids  of  the  glycols  are  called 
the  acids  of  the  oxalic  acid  series.  They  are  crystalline  sohds,  not 
volatile  without  decomposition,  and  generally  soluble  in  water.  As 
they  contain  two  hydroxyl  groups  they  are  diatomic,  and  as  they 
contain  two  carboxyl  groups  they  are  bibasic  and  form  neutral  and 
acid  salts  as  well  as  esters: 

HOOC-COOCC^Hs)  (C2H5)OOC-COO(C2H)6 

Primary  or  acid  ester.  Secondary  or  neutral  ester. 

The  amide  derivatives  are  similar  in  properties  and  method  of 
formation  to  the  amides  of  the  monobasic  acids.  On  account  of  the 
presence  of  the  two  carboxyl  groups  we  have  besides  the  real  amides 
(the  diamides)  also  acid  amides  or  amine  acids : 

(H2N)OC-CO(NH2)  (H3N)0C-C00H 

Oxamide.  Oxamic  acid. 

On  replacing  two  H  atoms  in  a  molecule  of  ammonia  by  a  divalent 

CO 
acid  radical  we  obtain  imides,  C2H4<pQ>NH,  succinic  acid  imide. 

These  derivatives  may  also  be  prepared  from  the  acid  and  neutral 
ammonium  salts  by  removing  water: 

Acid  ammonium  salts  minus  HjO  =  amic  acids: 

HOOC-COO-(NH,)  =  HOOC-CO-NH2 + H2O. 
Acid  ammonium  oxalate.  Oxamic  acid. 

Acid  ammonium  salts  minus  2H2O  =imides: 
Acid  ammonium  succinate.       Succinimide. 


OXALIC  ACID  SERIES.  421 

Neutral  ammonium  salts  minus  21120= amides: 

H,N-OOC-COO-NH, = NH^-OC-CO-NHj + 2H2O. 

Ammonium  oxalate.  Oxamide. 

Neutral  ammonium  salts  minus  4H20= niYriZes; 

H,N-OOC-COO-NH,=  NC-CN  +  4H20  (p.  423). 

Anhydrides  may  be  formed  similarly  to  the  oxyfatty  acids  even 
with  one  molecule  (see  Succinic  Acid),  when  the  carboxyls  occur 
united  to  different  carbon  atoms.  If  the  carboxyls  are  united  to  one 
C  atom,  then  on  heating  fatty  acids  are  obtained  and  at  the  same  time 
CO2  is  spUt  off:   HOOC-CHrCOOH^CHj-COOH+CO^. 

With  the  exception  of  oxalic  acid  all  the  acids  of  this  series  may 
be  considered  as  alkylene  dicarbonic  acids,  which  coincides  with  the 
methods  of  formation  and  with  their  decomposition. 

If  the  potassium  salts  are  decomposed  by  the  electric  current 
we  obtain  alkylenes,  carbon  dioxide,  and  potassium: 

C,H,<  ^gg|  =  C,H,+  2C0,+  2K. 

When  heated  with  alkali  hydroxides  they  decompose  into  ethanes 
and  carbon  dioxide;  thus  suberic  acid  yields  hexane: 

C«Hj2  <  COOH  ^  ^«^w  +  2CO2. 

The  possible  isomers  of  the  dibasic  acids  correspond  to  the  isomers 
of  the  alkylenes.  The  two  carboxyl  groups  may  be  united  to  two  different 
atoms  or  to  one  carbon  atom.  No  isomers  are  possible  of  the  first  two 
acids— oxalic  acid,  HOOC-COOH,  and  malonic  acid,  HOOC-CH2-COOH— 
while  two  are  possible  of  the  third  acid: 

HOOC-CH2-CH2-COOH     and    CH3-CH<^gggg. 
Ethylene  succinic  acid.  Ethylidene  succinic  acid. 

There  are  four  isomers  possible  of  the  fourth  member,  C3Hg(COOH)2, 
etc.  The  isomers,  which  have  both  carboxyl  groups  united  to  one  C  atom, 
may  be  said  to  be  derived  from  malonic  acid  (p.  423)  and  their  structure 
is  called  the  malonic  acid  structure. 

We  call  the  divalent  acid  residues  imited  with  the  two  hydroxyls  the 
acid  radicals  (p.  336): 

C0~  C0~  CO 

<QQ_oxalyl,   CH2<QQ_  malonyl,    C2H<<qq  succinyl. 

Preparation.  1.  If  the  halogen  alkylenes  are  heated  with  potassiupa 
cyanide  we  obtain  alkylene  cyanides,  which  yield  the  corresponding  acid 
on  boiling  with  acids  or  caustic  alkalies  (p.  346,  2) ; 


422  ORGANIC  CHEMISTRY. 

CN-CHj-CHa-CN + 4H2O  =  HOOC-CH2-CH2-COOH + 2NH,] 

Ethylene  cyanide.  Ethylene  succinic  acid. 

CN-CH(CN)-CH3  +  4H20=HOOC-CH(COOH)-CH3+2NH,. 

Ethylidene  cyanide.  Ethylidene  succinic  acid. 

2.  The  monohalogen  fatty  acids  are  transformed  into  the  cyanfatty 
acids  and  the  cyanogen  group  is  converted  into  the  carboxyl  group  by 
boiling  with  acids  or  caustic  alkahes: 

HOOC-CH2-CH2-CN  +  2H2O  =HOOC-CH2-CH2-CqOH  +  NH3; 

j9-Cyanpropionic  acid.  Ethylene  succinic  acid. 

HOOC-CH(CN)-CH3  +  2H20  =H00C7CH(C00H)-CH,  +  NH^ 

a-Cyanpropionic  acid.  Ethylidene  succinic  acid. 

3.  By  the  oxidation  of  the  acids  of  the  fatty  acid  and  oleic  acid  series 
as  well  as  of  neutral  fats  by  means  of  HNO3. 

4.  By  the  oxidation  of  the  normal  glycols  and  oxyfatty  acids  (men- 
tioned on  pp.  400,  402). 

5.  The  homologues  of  oxalic  acid  are  produced  from  malonic  acid 
ethyl-ester  in  a  similar  manner  to  acetic  acid  from  aceto-acetic  ester. 

Oxalic  Acid,  C2H2O4  or  HOOC-COOH.  Occurrence.  It  exists 
combined  as  acid  potassium  salt  in  many  plants,  such  as  in  the  varie- 
ties of  Runex  and  Oxalis,  from  whose  juice  oxaUc  acid  used  to  be 
obtaind  by  evaporation.  It  also  occurs  in  many  plants  as  calcium 
oxalate,  partly  in  solution  and  partly  as  crystals.  OxaHc  acid  also 
occurs  as  calcium  salt  in  the  animal  kingdom,  especially  in  normal 
and  pathological  urine,  as  urinary  sediment,  in  the  caterpillar  excre- 
ment, as  vesicle  calculi  (mulberry  calculus),  and  as  potassium  oxalate 
in  many  organs. 

Formation.  1.  By  passing  CO2  over  fused  sodium  we  obtain 
sodium  oxalate:    2CO2+ 2Na  =  CjNajOi. 

2.  From  fats,  carbohydrates  (sugar,  starch,  gums,  cellulose),  and 
many  other  organic  bodies  by  oxidation  with  nitric  acid.  On  fusing 
these  bodies  with  caustic  alkalies  we  obtain  alkali  oxalates. 

Preparation.  1.,  By  fusing  sawdust  (cellulose,  CgHioOs)  with 
alkaU  hydroxide  at  250°  to  300°  (p.  323) : 

C6H10O5+  H2O+  6NaOH  =  3C2Na20,+  18H. 

2.  By  heating  alkali  formates:  2H-C00Na  =  NaOOC-COONa 
+  2H. 

The  alkali  oxalate  thus  obtained  is  dissolved  in  water  and  the 
solution  mixed  with  calcium  hydroxide  (milk  of  Hme)  and  the  insoluble 
calcium  oxalate  which  separates  out  treated  with  sulphuric  acid 
when  insoluble  calcium  sulphate  precipitates  and  a  solution  of  oxalic 
acid  is  obtained. 


OXALIC  ACID  SERIES.  423 

Properties.  On  evaporating  an  aqueous  solution  fine  mono- 
clinic  crystals,  C2H2O4+  211^0,  separate  out.  On  heating  to  100°  C. 
or  drying  over  sulphuric  acid  we  obtain  anhydrous  oxalic  acid,  which 
appears  as  a  white  powder,  and  on  carefully  heating  to  150°  C. 
sublimes  and  on  rapidly  heating  decomposes  into  carbon  dioxide  and 
formic  acid  (p.  352):  C2H2O4  =  CH2O2+ CO2.  When  heated  with 
caustic  alkalies  it  splits  into  alkali  carbonate  and  hydrogen :  C2K2O4+ 
2K0H  =  2K2CO3+ 2H,  and  when  heated  with  concentrated  sul- 
phuric acid  it  decomposes  into  water,  carbon  monoxide,  and  carbon 
dioxide:   C2H204  =  CO+C024-H20. 

The  salts  of  oxalic  acid,  the  oxalates,  are,  with  the  exception  of 
the  alkali  salts,  insoluble  in  water  or  soluble  with  difficulty. 

Potassium  bioxalate,  CaHKO^  +  HgO. 

Potassium  quadr oxalate,  C2HKO4  +  C2H2O4+2H2O,  salt  of  sorrel,  forms 
colorless  crystals  soluble  in  water. 

Ammonium  oxalate,  C2(NH4)204,  forms  colorless  rhombic  crystals 
which  are  readily  soluble  in  water.  It  occurs  in  Peruvian  guano,  and 
splits  into  oxamide  and  water  on  being  heated : 

(H,N)00C-C00(NH4)  =  (H2N)-0C-C0(NH2)  4-2H2O. 

Oxamide,  C2(NH2)202,  is  a  white  powder  insoluble  in  water.  When 
heated  with  phosphorus  pentoxide  it  loses  2  mol.  H.JJ  and  oxalonitrile  ia 
produced  (cyanogen  gas) : 

(H2N)0C-C0(NH2)  =NC-CN  +  2H20. 

The  reverse  is  obtained  when  an  aqueous  solution  of  cyanogen  is 
allowed  to  stand  in  the  presence  of  mineral  acids  (p.  383). 

Ammonium  acid  oxalate,  C2H(NH4)04,  consists  of  colorless  crystals 
which  are  difficultly  soluble  in  water  and  yield  oxamic  acid  and  water 
on  being  heated: 

HOOC-COOCNHJ  =H00C-C0(NH2)  +  H2O. 

Oxamic  acid,  C2H(NH2)03,  is  a  white  insoluble  powder. 

Calcium  oxalate,  C2Ca04+H20  (p.  225),  is  precipitated  from  a 
calcium  salt  solution  by  oxalic  acid  or  an  oxalate  as  a  white  crystalline 
powder.  It  is  insoluble  in  acetic  acid  and  serves  in  the  detection 
of  oxalic  acid  as  well  as  for  the  soluble  calcium  compounds. 

Malonic  acid,  C3H4O4  or  HOOC-CH2-COOH,  is  obtained  on  the 
oxidation  of  ethylene  lactic  acid  (p.  407)  and  malic  acid  (p.  426).  It 
occurs  as  a  calcium  salt  in  the  sue:ar-beet  and  melts  at  132°  C.  All  com- 
pounds which  contain  two  COOH  groups  attached  to  the  same  C  atom 
split  off  1  mol.  CO2  on  heating.  Correspondingly  malonic  acid  decom- 
poses on  heating  into  CO2  +  CH3COOH. 


424  ORGANIC  CHEMISTRY. 

Malonic  acid  diethylester,  H5C2-OOC-CH2-COO-C2H5,  and  the  other 
esters  of  malonic  acid  are  used,  like  aceto-acetlc  ester  (p.  365),  for 
numerous  syntheses  as  the  H  atoms  of  the  methylene  group  are  readily 
replaceable  by  sodium  and  the  Na  then  readily  replaceable  by  radicals,  so 
that  by  this  means  a  large  number  of  higher  bibasic  acids  can  be  prepared. 

As  all  these  acids  contain  two  COOH  groups  united  to  the  same  C 
atom,  therefore  on  heating,  CO2  is  split  off  (see  Malonic  Acid) ;  hence 
the  malonic  acid  ester  syntheses  are  also  used  in  the  obtainment  of 
monobasic  acids: 

HOOC-CCCHg)  (C2H6)-COOH =HC(CH3)  (C2H5)COOH  +  CO^. 

Methyl  ethyl  malonic  acid.  Active  valeric  acid. 

Oxymalonic  acid,  tartronic  acid,  HOOC-CH(OH)-COOH  or  CjH.Og, 
is  obtained  from  brommalonic  acid,  as  well  as  in  the  oxidation  of  glycerine 
(p.  434)  and  the  tartaric  acids  (p.  428). 

Dioxymalonic  acid,  CgH^Og  or  H00C-C(0H)2-C00H.  This  acid 
may  be  considered  as  mesoxalic  acid  hydrate  (p.  434). 

Normal  Succinic  Acid,  Ethylendicarbonic  acid,  C4He04  or 
HOOC"C2H4~COOH.  Occurrence.  In  amber  (succinum,  fossil  conif- 
erous resin),  in  resin  and  turpentine  of  certain  conifers,  in  many  brown 
coals,  in  wormwood  and  poppy.  In  the  animal  kingdom  it  occurs 
in  the  thymus  gland,  spleen,  thyroid  gland,  hydrocele  and  echino- 
coccus  fluids,  sometimes  also  in  the  blood,  saUva,  and  urine.  It  is 
produced  to  a  sUght  extent  in  alcoholic  fermentation,  as  well  as  in 
the  putrefaction  of  meat. 

Preparation.  According  to  the  general  method  described  on 
page  421  as  well  as  by  heating  malic  or  tartaric  acid  with  hydriodic 
acid  (p.  427).  It  is  prepared  on  a  large  scale  by  the  dry  distillation 
of  amber  or  by  the  fermentation  of  calcium  malate  with  putrid  cheese 
at  30-40°  C. 

Properties.     Colorless  crystals  having  a  faint  acid  taste  and  soluble  in 

water  and  alcohol.     Its  salts  are  called  succinates.     Succinic  acid  melts 

at  180°  C.  and  distils  at  235°,  when  it  partly  splits  into  water  and  succinic 

CO 
anhydride,  CJ^^K^QyO.     Its    vapors    cause    coughing.      Heated   with 

bromine  it  yields  monobromsuccinic  acid,  C^HjBrO^,  and  dibromsuccinic 
acid,  C^H^BrgO^,  used  in  the  synthesis  of  malic  and  tartaric  acid.  All 
these  compounds  form  colorless  needles. 

Amidosuccinic  acid,  or  aspartic  acid,  HOOC~C2H3(NH2)~COOH, 

occurs  free  in  the  acid  secretion  of  many  sea-snails,  and  also  in 
beet-root  molasses,  and  is  split  off  from  proteins  by  treatment  with 
dilute  sulphuric  acid,  etc.  Nitric  acid  converts  it  into  malic  acid 
(p.  426).      It  is  obtained  from  asparagine  by  boihng  with  acids  or 


OXALIC  ACID  SERIES.  425 

alkalies  (see  below).     It  consists  of  rhombic  crystals  which  are  soluble 
in  hot  water. 

The  neutral  solution  is  dextrorotatory  at  ordinary  temperatures,  and 
inactive  at  75°  C,  while  at  higher  temperatures  it  is  Isevorotatory.  The 
acid  solution  is  dextrorotatory  and  the  alkaline  solution  Isevorotatory 
(p.  39). 

Asparagine,  HOOC~C2H3(NH2)~CO~(NH2),  amido-succinamic 
acid,  the  monamide  of  amidosuccinic  acid,  occurs  in  the  potato, 
beets,  asparagus,  hcorice,  marsh-mallow,  oyster-plant,  and  in  many 
other  plants,  especially  in  the  sprouts.  It  crystallizes  with  1  mol. 
HjO  as  colorless  prisms  from  the  pressed  juice  of  these  plants  on 
evaporation.  These  crystals  are  tasteless  and  Isevorotatory.  It  is 
readily  soluble  in  water  and  insoluble  in  alcohol  and  ether  and  forms 
salts  with  acids  as  well  as  with  bases. 

On  boiling  with  water,  but  quicker  with  acids  or  alkalies,  it  splits  into 
aspartic  acid: 

C,H3(NH,)<ggg^^^^  +H,0  =C,H3(NH,)  <gggH  +  NH»- 
Nitrous  acid  converts  it  into  malic  acid : 

QHgCNH^)  <c00i?''^  +2HNO,=  C2H3(OH)  <  c8oH  +  2H2O+  4N. 

Dextro-asparagine,  which  has  a  sweet  taste,  is  obtained  from  the 
wicken  sprouts  and  inactive  asparagine  is  prepared  synthetically, 

Isosuccinic  acid,  CH.rCH(C00H)2,  ethylidene  dicarbonic  acid,  is  ob- 
tained from  the  a-cyanpropionic  acid  (p.  422,  2)  and  forms  colorless  crystals, 
which  are  more  soluble  in  water  than  the  ordinary  succinic  acid.  It  melts 
at  130°  C.  and  decomposes  on  further  heating  into  carbon  dioxide  and 
propionic  acid. 

Pyrotartaric  acid,  CgHgO^  or  HOOC-CgHg-COOH.  Four  isomers  are 
possible  and  known,  according  to  the  structural  theory,  and  of  these  we 
must  mention: 

Common  pyrotartaric  acid,  CH3-CH(COOH)-CH2-COOH,  or  methyl 
succinic  acid,  is  produced  on  the  dry  distillation  of  tartaric  acid  (p.  428). 
It  melts  at  112°,  and  is  inactive  and  can  be  split  into  the  two  optically 
active  modifications. 

Normal  pyrotartaric  acid,  HOOC-H2C-CH2-CH2-COOH,  or  glutaric 
acid,  is  prepared  synthetically  and  melts  at  97°  C. 

Amido  normal  pyrotartaric  add,  amido  glutaric  acid,  glutamic  acid, 
HOOC-CH(NH2)-CH2-CH2-COOH,  occurs  with  aspartic  acid  in  many 
plants  and  in  beet-root  molasses,  and  is  obtained  with  other  amido  acids 
by  treating  proteins  (which  see)  with  dilute  sulphuric  acid,  etc.  It  forms 
rhombic  crystals  which  are  dextrorotatory  in  aqueous  solution.  The 
inactive  modification  13  also  known  and  the  Isevorotatory  modification 
can  be  obtained  from  this  by  the  action  of  molds. 


426  ORGANIC  CHEMISTRY. 

Glutamine,  HOOC-CH(NHj)-CIT2-CH2-CO(NH2).  Glutamic  acid 
amide  occurs  with  aspara^ine  in  many  plants  and  forms  colorless  needles 
wMch  are  dextrorotatory  in  acid  solution. 


10.  Malic  Acid,  Tartaric  Acid,  and  Citric  Acid. 

These  acids,  which  should  be  treated  of  in  connection  with  the 
trihydric  and  tetrahydric  compounds,  stand  in  very  close  connection 
to  succinic  acid,  hence  they  will  be  discussed  at  this  place. 

Malic  acid,  C^HeOs  or  H00C-CH(0H)-CH2-C00H,  oxysuccinic 
acid. 

Occurrence.     In  the  juice  of  most  sour  fruits. 

Preparation.  1.  From  unripe  apples,  grapes,  or  mountain  ash 
by  evaporating  the  juice  from  these,  filtering  and  precipitating  with 
lead  acetate.  The  precipitate  of  lead  malate  obtained  is  decom- 
posed by  H^S  :C,H,Pb05+H2S=C4HA+PbS.  The  PbS  is  filtered 
off  and  the  filtrate  evaporated  to  point  of  crystallization. 

Formation.  1.  By  treating  asparagine  (p.  425)  or  aspartic  acid  (p.  424) 
with  nitrous  acid : 

Aspartic  acid.  Malic  acid. 

2.  By  boiling  bromsuccinic  acid  with  silver  hydroxide: 

C,H3Br  <  gggg  +  AgOH  =C,H3(0H)  <  gggg  +  AgBr. 

If  malic  acid  is  heated  with  hydriodic  acid  (p.  427)  succinic  acid  is  ob- 
tained; also  in  the  fermentation  of  calcium  malate. 

3.  On  heating  tartaric  acid  with  HI  (p.  427). 

Properties.  Malic  acid  is  a  trihydric,  bibasic  (p.  335)  acid; 
forming  white  needle-shaped,  deliquescent  crystals  having  a  pleasant 
acid  taste.     It  is  oxidized  by  chromic  acid  into  malonic  acid: 

C,H3(0H)  <  ^gg|  +  20  =  CH,  <  ^ggg_^  C0,+  H,0. 

Natural  malic  acid  is  laevorotatory,  while  that  obtained  from  dextro- 
tartaricacid  is  dextrorotatory  and  that  from  succinic  acid  derivatives  is 
optically  inactive.  This  inactive  modification  splits  into  the  dextro  and 
laevo  forms  (p.  39).  The  salts  of  malic  acid  are  called  malates  and  are 
readily  soluble  in  water  with  the  exception  of  the  lead  salt. 


TARTARIC  ACIDS.  427 

Ferrous  and  ferric  majate  occur  to  about  30  per  cent,  in  the  extract 
obtained  from  powdered  iron  and  crushed  sour  apples. 

Fumaric  acid  and  maleic  acid,  HOOC-CH=CH-COOH  or  C,H,0,. 
Malic  acid  decomposes  on  heating  into  these  two  stereoisomeric,  dibasic 
acids  (structure,  p.  308). 

Fumaric  acid  occurs  free  in  many  plants;  thus,  in  Fumaria  officinalis, 
in  Iceland  moss,  and  in  certain  fungi,  especially  in  champignons.  It  sub- 
limes at  200°  C.  without  melting  and  is  difficultly  soluble  in  water  and 
is  non-poisonous. 

Maleic  acid  melts  at  130°  C,  is  readily  soluble  in  water,  and  is  poison- 
ous. Both  these  acids  are  converted  into  ordinary  succinic  acid  by  nascent 
hydrogen  and  into  malic  acid  on  heating  with  water;  on  the  electrolysis  of 
their  salts  acetylene  is  produced:  QHjjKaO^  =  CjHj  +  2CO2  +  2K. 

Tartaric  acid,  C^HeOe  or  HOOC-CH(OH)-CH(OH)-COOH, 
dioxysuccinic  acid,  is  tetrahydric  and  bibasic.  Four  tartaric  acids  of 
the  same  structure  are  known,  namely,  dextrotartaric  acid,  laevo- 
tartaric  acid,  inactive  racemic  acid  (which  can  be  split),  and  inactive 
meso tartaric  acid  (which  cannot  be  split)  (p.  306),  which  differ  from 
each  other  chiefly  by  optical  properties  and  which  can  be  trans- 
formed into  one  another.  If  solutions  of  equal  amounts  of  dextro- 
and  Isevotartaric  acids  are  mixed  and  evaporated  we  obtain  racemic 
acid,  which  is  readily  split  into  the  above  acids.  If  dextro-  or 
Isevotartaric  acid  is  heated  with  water  to  170°  or  boiled  for  a  longer 
time  with  an  excess  of  caustic  alkali  they  become  inactive,  as  one-half 
of  the  respective  acid  is  changed  to  the  variety  having  the  opposite 
rotation;  hence  on  evaporation  we  obtain  racemic  acid.  In  these 
operations  some  mesotartaric  acid  is  also  alway  produced,  which  under 
the  same  conditions  is  in  part  converted  into  racemic  acid  (equilib- 
rium condition,  p.  62). 

Synthetically  a  mixture  of  optically  inactive  racemic  and  mesotartaric 
acids  are  obtained  by  boiling  dibromsuccinic  acid  with  moist  silver  oxide: 


CHBr-COOH  CH(OH)-COOH 

I  +2AgOH=l 

CHBr-COOH  CH  (OH)-COOH 


On  heating  with  HI  the  tartaric  acids  first 'yield  malic  acid  and  then  suc- 
cinic acid: 

CA(OH),<gggg  +  2HI=C,H3(OH)<gggg  +  H,0  +  2I; 

Tartaric  acid .  Malic  acid. 

C,H3(0H)  <  ggg^  +  2HI =C,H,  <  ggg][^  +  H,0  +  2l 

Malic  acid.  Succinic  acid. 


428  ORGANIC  CHEMISTRY. 

On  oxidation  the  tartaric  acids  yield  bibasic  dioxytartaric  acid, 
HOOC-CO-CO-COOH  (p.  443),  or  tartronic  acid,  HOOC-CH(OH)-COOH 
(p.  434),  and  then  COj  and  formic  acid.  When  fused  and  then  cooled  they 
give  the  isomer  metatartaric  acid,  C^HgOg,  an  amorphous  deliquescent 
mass;  at  180°  soluble  tartaric  anhydride,,  tartrelic  acid,  C^H^Oj,  forming 
deliquescent  crystals,  is  obtained.  On  heating  further  until  the  mass 
becomes  infusible,  insoluble  tartaric  anhydride,  C^H^Og,  a  white  powder, 
is  produced.  These  three  compounds  are  reconverted  into  tartaric  acid 
by  boiling  with  water. 

On  further  heating  tartaric  acids  they  give  off  an  odor  of  burnt  sugar, 
and  amongst  other  bodies  we  find 

Pyrotartaric  acid,  CgH^O,  or  HOOC-C,H--COOH  (p.  425),  and 

Pyroracemic  acid,  C.H.Oj  or  CH3-CO-COOH  (p.  403). 

1.  Mesotartaric  acid,  antitartaric  acid.  Preparation.  From  dribomsuc- 
cinic  acid  (besides  racemic  acid,  see  p.  427),  also  by  the  oxidation  of 
erythrite,  sorbite,  maleic  acid,  and  phenol. 

Properties.  Colorless  plates  having  the  formula  CJifi^  +  HgO.  It  forms 
a  potassium  acid  salt  which  is  more  soluble  than  the  corresponding 
salts  of  the  other  tartaric  acids.  It  is  optically  inactive  and  cannot  be 
transformed  into  active  tartaric  acids  (p.  306,  a),  but  it  may  be  converted 
into  racemic  acid. 

2.  Racemic  acid.  Occurrence.  Sometimes  in  the  mother-hquor  of 
crude  tartar. 

Preparation.  From  dextrotartaric  acid  (p.  427),  also  by  the  oxida- 
tion of  mannite,  dulcite,  or  mucic  acid  and  fumaric  acid.  Synthetically, 
besides  mesotartaric  acid,  from  dibromsuccinic  acid  and  also  by  boiling 
glyoxal  with  hydrocyanic  acid  and  hydrochloric  acid: 

^COH  ,  ^„p^  ,  .XT  o      .CH(OH)COOH  ,  ^T^xT 
<COH  +  2^^^  +  ^^20=  <CH(OH)COOH  +  2^^3. 

Properties.  Colorless,  triclinic,  optically  inactive  crystals,  crystallizing 
with  1  mol.  HgO.  It  is  less  soluble  than  dextro-  or  laevotartaric  acids 
in  water,  and  its  calcium  salt  (calcium  racemate)  is  precipitated  from 
solutions  of  the  free  acid  by  the  addition  of  CaClj  in  contradistinction  to 
the  other  tartaric  acids.  In  watery  solution  it  completely  decomposes 
into  its  components  dextro-  and  laevotartaric  acids,  which  can  be  separated 
from  each  other  by  the  following  method: 

One-half  of  a  racemic  acid  solution  is  saturated  with  ammonia  and  the 
other  half  with  caustic  soda.  These  two  solutions  are  mixed  and  allowed 
to  crystallize,  when  we  obtain  two  varieties  of  crystals  of  C4H<Na(NH^)0e, 
which  differ  from  each  other  by  some  having  a  certain  small  face  on 
the  right  side  and  others  having  the  same  face  on  the  left  side  (p.  305). 
If  these  crystals  are  separated  we  find  that  the  first  are  dextrorotatory 
and  is  the  salt  of  dextrotartaric  acid,  while  the  other  is  Isevorotatory 
and  is  the  salt  of  laevotartaric  acid. 

3.  Laevotartaric  acid.  This  acid  behaves  exactly  like  dextrotartaric 
acid  with  the  exception  of  its  laevorotatory  power  and  the  above-men- 
tioned shape  of  the  crystals  of  its  salts. 

4.  Dextrotartaric  Acid,  Ordinary  Tartaric  Acid.  Occurrence.  Free 
and  as  acid  potassium  salt  widely  distributed  in  the  vegetable  king- 


TARTARIC  ACIDS.  429 

dom,  especially  in  the  juice  of  the  grape.  The  alcohol  produced  in 
the  fermentation  of  the  grape-juice  precipitates  the  acid  potassium 
tartrate.  This  deposit  from  wine  is  called  crude  tartar  and  forms 
gray  or  reddish  crystalline  crusts  which  also  contain  calcium  tartrate 
and  yeast  residues,  etc. 

Preparation.  The  crude  tartar  is  boiled  with  water,  and  chalk, 
producing  soluble  neutral  potassium  tartrate  and  insoluble  calcium 
tartrate : 

2C,H5KOe+  CaCOg  =  C4H4K,Oe+  aH,CaOe+  JIfi+  CO^. 

Potassium  Potassium  Calcium 

bitartrate.  tartrate.  tartrate. 

The  dissolved  potassium  tartrate  is  precipitated  as  calcium  tar- 
trate by  the  addition  of  calcium  chloride  solution.  The  combined 
precipitates  of  calcium  tartrate  are  decomposed  by  sulphuric  acid, 
the  calcium  sulphate  filtered  off,  and  the  filtrate  containing  the  free 
tartaric  acid  evaporated  to  crystallization: 

CH.KPe+CaCl^  =C,H4CaOe+2KCl. 
C4H,CaOe+  H2SO4  =  C,H606+  CaSO^. 

Properties.  Tartaric  acid  is  tetravalent  and  bibasic,  and  forms 
large  monoclinic  prisms  which  melt  at  170°  and  are  readily  soluble 
in  water  and  alcohol  but  difficultly  soluble  in  ether.  Its  solutions  are 
dextrorotatory.     Its  salts  are  called  tartrates. 

Acid  potassium  tartrate,  C4H5KO6,  cream  of  tartar,  potassium 
bitartrate,  is  obtained  by  the  recrystallization  of  crude  tartar  (see 
above) .  It  is  a  white  crystaUine  powder  not  readily  soluble  in  water, 
and  is  precipitated  from  concentrated  potassium  salt  solutions  by 
the  addition  of  an  excess  of  tartaric  acid  solution,  hence  potassium 
salts  are  used  in  detecting  tartaric  acid.  The  must  from  the  tropi- 
cal tamarind  is  rich  in  potassium  acid  tartrate,  malic,  tartaric,  and 
citric  acids,  besides  sugar. 

Potassium  tartrate,  2C4H4K2O6+H2O,  consists  of  neutral  crystals 
soluble  in  0.7  part  water. 

Sodium-potassium  tartrate,  C4H4KNa06+4H20,  Rochelle  salts, 
is  obtained  by  saturating  a  potassium  acid  tartrate  solution  with 
soda.     It  consists  of  colorless  crystals  soluble  in  1.4  parts  water: 

2  g>C4H40e+  Na^CO,  =  2 1^> C4H40e-4-H,0+  CO^. 


430  ORGANIC  CHEMISTRY, 

Effervescent  powder  is  a  mixture  of  tartaric  acid,  sodium  bicarbonate, 
and  sugar. 

Seidlitz  powders  contain  sodium  bicarbonate  and  sodium  potassium 
tartrate  mixed  together  in  one  paper  and  tartaric  acid  in  the  second 
paper.  When  the  contents  of  the  two  papers  are  mixed  with  water 
sodium  tartrate  is  proiuced  and  carbon  dioxide  is  evolved  with  effer- 
vescence. 

Potassio-antimonous  Tartrate,  2C,H,K(SbO)06  +  H^O,  Tartar- 
emetic.  In  this  compound  the  H  atom  of  one  carboxyl  is  replaced 
by  the  monovalent  group  antimonyl,  SbO  (p.  180).  It  is  obtained 
by  boihng  potassium  acid  tartrate,  antimony  oxide,  and  water, 
filtering  and  evaporating  the  solution  until  white,  sweet  crystals  are 
obtained  which  are  soluble  in  17  parts  water  and  which  cause 
vomiting: 

2  ^  >  C,H,Oe+  Sb,03  =  2  g^Q  >  C,H,Oe+  H,0. 

Calcium  tartrate,  C^H^CaOa  +  4H2O,  precipitates  from  neutral  tartrate 
solutions  by  the  addition  of  calcium  chloride  as  a  white  crystalline  powder 
which  is  soluble  in  dilute  acids.  Cold  solutions  of  alkalies  also  dissolve  it, 
but  on  boihng  the  solution  it  precipitates  again  (separation  from  malic 
and  citric  acids). 

Aluminium  aceto-tartrate,  Alj(C2H302)2(C4H^Oe)(OH)2,  alsol,  forms 
colorless  gummy  masses  wnich  are  soluble  in  water. 

Borax-tartar,  KNaC4HPe  +  2K(Bo>C4H,06,  is  obtained  by  dissolv- 
ing borax  and  cream  of  tartar  in  water  and  evaporating  to  dryness. 

Citric  acid,  C^HgO^or  CH2(COOH)-C(OH)(COOH)-CH2(COOH), 
oxypropantricarbonic  acid,  on  account  of  its  occurrence  and  behavior 
on  heating,  etc.,  will  be  treated  of  here. 

Occurrence.  Free  in  the  lemon,  currant,  cranberry,  and  other  sour 
fruits,  in  the  beet-root,  and  to  a  slight  extent  in  milk. 

Preparation.  1.  From  lemon-juice  by  neutrahzing  with  lime  and 
heating  to  boiling,  when  calcium  citrate  (p.  431)  separates  out. 
This  is  decomposed  by  dilute  sulphuric  acid,  the  calcium  sulphate 
formed  filtered  off,  and  the  filtrate  evaporated  to  crystaUization. 

2.  By  fermenting  a  grape-sugar  solution  by  means  of  the  Saccha- 
romycetes  citromyces. 

Formation.  Synthetically  from  dichloracetone,  CHgCl-CO-CHjCl 
which  is  converted  into  CH2-C1-C(0H)(CN)-CH2C1  by  HCN  (p.  371  1)„ 
and  this  then  transformed  by  HCl  into  dichloracetonic  acid, 
CH2Cl-C(OH)(COOH)-CH2Cl  (p.  346,  2).      On  treating  this  with  KCN 


CITRIC  ACID,  431 

the  chlorine  is  replaced  by  CN  and  if  this  product  is  heated  again  with 

HCl  citric  acid  is  obtained : 

CHjCCN)  -  C(OH)  (COOH)  -  CHjCCN)  +4H2O  = 
CHjCCOOH)  -  C(0H)  (COOH)  -  CHjCCOOH) + 2NH3. 

Properties.  Large  colorless  rhombic  prisms  with  1  mol.  H2O, 
which  melt  at  100°  and  lose  their  water  of  crystalHzation  at  150°.  On 
further  heating  it  forms  aconitic  acid,  CeHgOj,  then  itaconic  acid  and 
mesaconic  acid,  CsHeO^  (see  below).  Citric  acid  is  readily  soluble  in 
water  and  alcohol.  It  is  tetravalent  and  tribasic  and  hence  forms 
three  series  of  salts  {citrates)  and  esters.  On  oxidation  it  yields  oxalic 
acid,  acetic  acid,  and  acetone. 

Calcium  citrate,  Ca3(C8H507)2  +  4H20,  is  not  readily  soluble  in  cold 
water,  but  insoluble  in  hot  water ;  hence  a  cold  saturated  solution  precipi- 
tates completely  on  boiling  (detection  of  citric  acid). 

Magnesium  citrate,  Mg3(C8H5R7)2  +  14H20,  mixed  with  citric  acid, 
sodium  bicarbonate  and  sugar,  forms  the  ordinary  effervescent  magnesia 
or  magnesii  citras  effervescens. 

Silver  citrate,  itrol,  Kgf^^^O^,  is  a  colorless  powder. 

Ferric  citrate,  Fe(C8H507)  +  3H20,  is  obtained  by  dissolving  ferric 
hydroxide  in  citric  acid  and  evaporating,  when  an  amorphous  brown  mass 
soluble  in  water  is  obtained.  Iron-ammonium  citrate,  2Fe(C6H507) -f- 
(NH4)2CeH807  +  2H2O,  forms  amorphous  brownish-red  masses  soluble  in 
water. 

Tricarballylic  acid,  propantricarbonic  acid,  CgHgOo  or  C3H5(COOH)3, 
occurs  in  unripe  beet-root  and  is  prepared  from  aconitic  acid  (see  below) 
by  the  action  of  nascent  hydrogen  or  by  heating  citric  acid  with  HI. 

Aconitic  acid,  equisetic  acid,  CeHgOg  or  C3H3(COOH)3.  ^  This  tribasic 
acid  occurs  in  Aconitum  napellus,  Equisetum  fluviatile,  in  sugar-cane, 
and  in  the  sugar-beet,  and  is  produced  by  heating  citric  acid  to  175°: 

C3H,(0H)  (C00H)3 = C3H3(COOH)3 + HjO. 

Itaconic  acid,  methylene  succinic  acid,  CjHgO^  or  CH3==C2H2(COOH)2, 
and  its  isomer. 

Citraconic  acid,  methylmaleic  acid,  CjHjOi,  are  obtained  by  heating 
citric  or  aconitic  acid  above  175°. 

Mesaconic  acid,  methylfumaric  acid,  HOOC- (CH3)C  =  CH-C00H 
or  C5He04,  a  stereoisomer  of  citraconic  acid  is  prepared  by  heating 
itaconic  or  citraconic  acids  with  water  to  200°. 

COMPOUNDS  OF  TRIVALENT  ALCOHOL  RADICALS. 
I.  Trivalent  Alcohol  Radicals. 

General  formula  CnH2n-  1. 
These,  like  all  radicals  with  uneven  valence,  do  not  exist  free; 
They  are  called  methenyl,  ethenyl,  propenyl,  etc.,  or  glyceryl,  butenyl. 


432  ORGANIC  CHEMISTRY. 

crotonyl,  etc.  The  trivalent  compounds  are  derived  from  the  satu- 
rated hydrocarbons  in  a  manner  similar  to  that  of  the  mono-  and  di- 
valent compounds  in  that  three  atoms  are  replaced  by  other  atoms 
or  by  atomic  groups.  The  relationship  of  these  compounds  to  each 
other  is  simply  as  follows: 

Propyl  alcohol,       CgHgO.  Propionic  acid,  CjHeOj. 

Propylene  alcohol,  CgHgOj.  Lactic  acid,         CgHeOg. 

Propenyl  alcohol,    CgHgOg.  Glyceric  acid,      C3H6O4. 


2.  Trihydric  AlcohoU. 

General  formula  CnH2n-i(OH)3. 

The  properties  which  the  glycols  show  is  also  found  in  the  tri- 
hydric and  polyhydric  alcohols,  and  these  become  more  and  more 
pronounced  as  the  number  of  hydroxyl  groups  increases.  Thus  from 
glycerine  on  oxidation  we  obtain  a  trihydric,  monobasic  acid,  as  well  as 
a  trihydric,  dibasic  acid;  also  aldehyde  alcohols,  ketone  alcohols,  etc. 
(p.  337).  We  do  not  know  of  any  trihydric  alcohols  containing  less 
than  three  C  atoms  (p.  331). 

Glycerine,  C3H5(OH)3  or  CH,(0H)-CH(0H)-CH2(0H),  Propenyl 
Alcohol,  Glycerol.  Occurrence.  It  is  the  only  trihydric  alcohol  found 
in  nature  and  occurs  as  glycerine  acetate  (triacetin),  €3115(0211302)3, 
in  ethereal  oils  of  the  spindle-tree,  and  forms  esters  with  the  higher 
fatty  acids  and  oleic  acid,  which  constitute  the  animal  and  vegetable 
fats.  It  is  produced  to  a  slight  extent  in  alcoholic  fermentation  and 
hence  exists  in  beer  and  wine. 

Preparation.  1.  As  a  by-product  in  the  manufacture  of  soaps 
and  plasters,  where  the  fats  (fatty  acid  esters  of  glycerine)  are  decom- 
posed by  alkalies  or  lead  hydroxide  in  a  manner  similar  to  other 
esters  (p.  357,  2).  It  is  formed,  for  example,  when  fats  are  boiled  with 
lead  hydroxide,  producing  an  insoluble  lead  salt  of  the  fatty  acids 
and  glycerine: 

2C3H5(C,3H3s02)3+  3Pb(OH)2  =  2CgH5(OH)g-f-  3Pb(QgHg,02),. 

Tristearin. 

2.  As  a  by-product  in  the  manufacture  of  stearin  candles  (p.  440), 
where  fats  are  treated  with  superheated  steam  or  warmed  with  con- 


I 


GLYCERINE.  433 

centrated  sulphuric  acid  to  120°  C,  when  the  fat  takes  up  water  and 
splits  into  glycerine  and  the  fatty  acids  which  separate  out : 
C3H,(C,«H330,)3+  3H,0  ==  C3H,(OH)3+  '^C,,^,fi,. 

Tristearin.  Glycerine.         Stearic  acid. 

The  solution  of  glycerine  thus  obtained  according  to  methods  1  or  2 
(after  neutralization  or  removal  of  dissolved  lead  oxide  by  HjS)  is  care- 
fully concentrated  by  evaporation,  the  salts  which  separate  removed 
by  filtration,  and  the  crude  glycerine  thus  obtained  purified  by  distillation 
with  superheated  steam. 

Synthetically.  Propenyl  bromide  with  silver  acetate  yields  glycerine 
acetic  acid  ester,  which  is  saponified  by  bases: 

CaH.Br^  +  3  AgC,H30,= C3H,(C,H30,)3  +  3AgBr; 
C^YL,{C^YLJd,),  +  3K0H  =  C3H5(OH)3  +  3KC2H3O2. 

Or  propenyl  chloride  is  heated  with  water  to  170°: 

C3H5CI3  +  3H0H  =  C3H,(OH)3  +  3HC1. 

Properties.  Thick,  colorless,  sweet  (hence  the  name)  liquid 
having  a  specific  gravity  of  1.27,  and  when  free  from  water  it  solidifies 
to  a  white  crystalline  mass  at  0°  C.  It  distils  without  decomposition 
at  290°  C,  and  is  soluble  in  water  and  alcohol  but  insoluble  in  ether 
and  fatty  oils.  It  dissolves  the  alkalies  and  alkaline  earths  and 
many  metallic  oxides,  forming  compounds  similar  to  the  alcoholates. 
With  dehydrating  agents  it  gives  acrolein,  C3H4O  (p.  439),  and  when 
carefully  oxidized  it  gives,  according  to  the  conditions,  aldehydes  and 
acids  or  mixed  compounds.  As  glycerine  contains  three  hydroxyl 
groups,  it  forms  three  series  of  esters  (the  glycerides)  and  mixed 
ethers. 

3.  Derivatives  of  Trivalent  Alcohols. 

Glyceric  aldehyde,  CgHeOg  or  CH0-CH(0H)-CH20H,  is  an  aldehyde 
alcohol  and  forms  colorless  sweet  crystals. 

Dioxyacetone,  CHg-OH-CO-CHgOH,  the  isomeric  ketone  alcohol, 
forms  sweet  crystals. 

Both  compounds  are  obtained  as  a  mixture  (called  glycerose)  by 
the  careful  oxidation  of  glycerine.  They  readily  unite,  forming  inactive 
Isevulose,  CeHigOe,  also  called  a-acrose.  Glyceric  aldehyde  and  dioxy- 
acetone are  true  sugars  (carbohydrates)  according  to  their  constitution 
(p.  402),  and  can  only  be  obtained  pure  in  an  indirect  manner. 

Glyceric  acid,  dioxypropionic  acid,C3H60,orCH2-OH-CH-OH-COOH, 
is  produced  on  the  oxidation  of  glycerine  by  dilute  nitric  acid.  It  fornis 
an  inactive  sirup  which  is  readily  soluble  in  water  and  alcohol.  It  is 
converted  into  the  laivorotatory  modification  by  Penicillium  glaucum,  and 
on  being  heated  it  splits  into  water  and  pyroracemic  acid: 

C3H«0,=H,0+C3H,03- 


I 


434  ORGANIC  CHEMISTRY. 

Tartronic  acid,  oxymaloni^  acid,  HOOO-CHOH-COOH  or  CgH^Og, 
is  obtained  by  oxidizing  glycerine  witii  potassium  permanganate  and 
forms  color'esi  readily  soluble  crystals. 

Mesoxalic  acid,  HOOC-CO-COOH,  is  produced  in  the  oxidation  of 
glycerine  esters  by  cold  nitric  acid  and  by  the  action  of  baiyta-water 
upon  alloxan  or  dibrommalonic  acid.  It  can  only  be  obtained  with 
1  mol.  HgO;  hence  it  may  also  be  considered  as  dioxymalonic  acid, 
H00C-C(0H)2-C00H  (p.  424). 

Glycerine  ethers  may  be  obtained  by  the  action  of  potassium  alcoholates 
upon  the  haloid  esters  of  glycerine.  They  are  colorless  liquids  having 
a  faint  ether-like  odor: 

Ethylin,C3H,<(gH),^^^         Diethylin,  C3H,<  (g^)^^^^^ 

Triethylin,  C^,{OG^,\ 


Glycerine  anhydride,  glycid  alcohol,  OCHa-CH-CHjOH,  is  pro- 
duced from  monochloriiydrin  (see  below)  by  the  action  of  Ba(0H)2.     It  is 

a  liquid,  boihng  at  162°,  whose  hydrochloric  acid  ester,  O '  CH2~CH-CH2C1, 
epichlorhydrin,  as  well  as  dichlorhydrin  (see  below),  has  techincal  uses. 

Glycerine  hydrochloric  acid  ester,  chlorhydrins,  are  produced  by  the 
action  of  H(J1  upon  glycerine.  Dichlorhydrin,  CHaCl-CHOH-CHjCl, 
is  a  solvent  for  resins,  colors,  cellulose  nitrates,  etc. 

Glycerine  trinitrate,  C3H5(N03)3,  incorrectly  called  nitroglycerine, 
is  obtained  by  dropping  glycerine  into  a  cooled  mixture  of  sulphuric 
and  nitric  acids.  It  is  a  colorless,  odorless,  poisonous,  viscous  liquid 
which  is  difficultly  soluble  in  water  but  readily  soluble  in  alcohol, 
ether,  chloroform,  and  crystaUizes  at  — 20°  C.  It  is  used  in  medicine 
under  the  name  glonoinum.  On  suddenly  heating,  as  well  as  by  a 
blow  or  shock,  it  explodes  violently  (Nobel's  explosive  oil),  and  when 
mixed  with  infusorial  earth  (p.  195)  it  forms  a  pasty  mass  called  dyna- 
mite which  does  not  explode  by  shock  alone  or  by  ignition,  but  is 
ignited  by  mercury  fulminate;  hence  it  serves  as  an  important  explo- 
sive. Mixtures  with  cellulose  nitrates  are  used  for  the  same  purposes 
as  dynamite. 

1  gramme  of  glycerine  trinitrate  yields  on  explosion  1300  cc.  gas 
measured  at  0°  and  760  mm.  pressure.  As  a  rise  in  temperature  takes 
place  on  explosion,  the  gases  expand  to  about  10,500  cc.  (p.  207). 

Glycero-phosphoric  acid,  C3H5(OH)2(H2POJ,  occurs  in  the  urine 
and  is  the  basis  on  which  the  lecithins  are  formed,  and  certain  of  its  salts 
are  used  in  medicine 

Lecithins  occur  as  such  or  as  a  constituent  of  the  lecithalbumins 
(see  Proteids)  and  protagons  (see  Glucosides)  in  all  animal  fluids,  and 
especially  in  the  nerve  and  brain  substance,  thymus  glands,  egg-yolk 
(7-10  per  cent.),  and  to  a  less  extent  in  semen,  pus,  blood,  milk,  yeast, 
corn,  peas,  wheat,  etc. 


FATS.  435 

It  is  a  wax-like  neutral  solid,  readily  soluble  in  alcohol  and  ether, 
readily  decomposable,  and  combines  with  acids  and  alkalies. 

On  boiling  with  acids  or  baryta-water  they  decompose  into  choline, 
(HO*C2H4)N(CH3)3(OH),  glycero-phosphoric  acid,  palmitic  and  stearic 
acids,  or  oleic  acid,  CjgH^Oa,  and  therefore  the  following  formula  can 
be  given  as  their  structure; 

(CNH2N-i02)rC3H,-HPO,-C2H,-N (CHg),-  OH. 

Glyceryl  palmitate,  palmitin,  C3H5(Ci6H3i02)3,  crystaUizes  in 
shining  leaves  which  melt  at  63°  C. 

Glyceryl  stearate,  stearin,  C3H5(Ci8H3502)3,  also  crystaUizes  in 
shining  leaves  and  melts  at  67°  C. 

Glyceryl  oleate,  olein,  C3H5(Ci8H3302)3,  forms  an  oily  Uquid  (p. 
440)  which  solidifies  at  -  6°  C. 

These  three  esters  may  be  obtained  by  heating  glycerine  with 
the  respective  acids  and  mixed  together  form  the  chief  constituent 
of  all  animal  and  vegetable  fats,  which  are  divided  into  three 
classes,  namely,  tallows  (solid),  butter  and  lard  (semi-sohd),  and 
oils  (liquids).  Oils  contain  chiefly  olein,  while  the  tallows  contain 
stearin  chiefly. 

The  Fats  in  General.  The  fats  are  obtained  by  pressure  or  by  extraction 
with  ether,  carbon  disulphide,  etc.  Butter  is  prepared  by  violently  beat- 
ing milk,  when  the  fat  globules  conglomerate.  Artificial  butter  or  mar- 
garine is  obtained  by  trying  out  animal  fat  and  allowing  it  to  cool,  and 
then  exposing  it  to  pressure,  which  frees  the  fat  of  stearin  and  yields  an  oil 
(oleomargarine-oil).  This  oil,  which  is  a  mixture  of  olein  and  palmitin  is 
strongly  shaken  with  warm  milk  in  a  method  similar  to  the  manufac- 
ture of  butter,  when  the  artificial  butter  separates.  This  is  colored 
yellow  and  treated  with  butyric  acid  esters. 

The  fats  when  pure  are  colorless,  odorless,  and  tasteless  neutral  bodies 
insoluble  in  water,  not  readily  soluble  in  alcohol,  but  readily  soluble  in 
ether  and  carbon  disulphide.  They  are  lighter  than  water  and  produce 
a  transparent  stain  when  applied  to  paper  which  does  not  disappear  on 
warming  (differing  from  the  ethereal  oils).  They  can  be  heated  to  300°  C. 
without  suffering  any  change,  but  at  higher  temperatures  they  decompose, 
yielding  various  products  having  an  unpleasant  odor,  chief  amongst  which 
IS  acrolein. 

Many  fats  when  exposed  to  the  air  are  gradually  converted  into  a  hard 
transparent  mass.  These  are  called  drying  oils;  for  instance,  hemp-seed 
oil,  croton-oil,  linseed-oil,  poppy-oil,  nut-oil,  which  consist  chiefly  of  the 
glycerides  of  linoleic  acid,  CigHggOa  (p.  445),  as  well  as  castor-oil.  These 
unsaturated  glycerides  become  solid  on  absorbing  oxygen. 

The  other  fats  do  not  change  when  pure,  but  as  they  generally  consist 
of  mixtures,  especially  with  proteids,  they  gradually  suffer  decomposition 
becoming  disagreeable  in  taste  and  smell  and  having  an  acid  reaction,  i.e., 
they  become  rancid.     This  depends,  upon  the  setting  free  of  fatty  acids 


436  ORGANIC  CHEMISTRY, 

and  the  formation  of  aldehydes  by  the  action  of  the  oxygen  of  the  air  and 
light,  which  cause  the  odor  and  taste.  The  fats  are  split  into  glycerine  and 
fatty  acids  or  fatty  acid  salts  by  superheated  steam,  strong  acias,  or  bases 
(see  Soaps),  as  well  as  by  the  steatolytic  enzyme  of  the  pancreatic  juice. 

Solid  Fats.     Lard  contains  about  60  per  cent,  olein. 

Mutton  tallow  contains  about  75  per  cent,  palmitin  and  stearin  and 
25  per  cent,  olein.  When  mixed  with  2  per  cent,  salicylic  acid  it  forms 
salicylic  tallow. 

Cacao-butter,  obtained  from  the  seeds  of  the  Theobroma  Cacao  by 
pressure,  consists  of  olein,  pahnitin,  stearin,  and  theobromic  acid  glycerine 
(p.  377). 

Nutmeg-butter,  obtained  from  the  nutmeg  by  pressure,  consists  of 
myristicin,  olein,  and  ethereal  oils. 

Cocoanut-oil,  the  fat  of  the  seed-kernel  of  the  Cocos  nucifera,  consists 
of  laurin,  myristin,  and  palmitin. 

Liquid  Fats.  Olive-oil  is  obtained  from  the  olives  by  pressure.  Olive- 
oil  treated  with  6  per  cent,  oleic  acid  is  used  in  medicine  under  the  name 
lipanin. 

Almond-oil  is  obtained  by  pressing  the  sweet  or  bitter  almond. 

Poppy-oil  is  produced  by  pressing  the  poppy-seed. 

Linseed-oil,  from  the  flaxseed. 

Laurel-oil,  obtained  from  the  fresh  ripe  laurel  by  pressure,  consists  of 
laurin. 

Rape-seed  oil,  from  the  seeds  of  the  rape. 

Castor-oil,  from  the  seeds  of  the  Ricinus  communis,  contains  chiefly 
glycerids  of  ricinoleic  acid. 

Croton-oil,  from  the  seeds  of  the  Croton  tiglium,  also  contains  the 
poisonous  glyceride  of  the  little-known  crotonolic  acid,  but  not  of  cro- 
tonic  acid  (p.  440). 

Cod-liver  oil,  from  the  fresh  livers  of  the  codfish  by  gently  heating. 

Sesame  oil,  from  the  seeds  of  the  Sesamum  orientale,  is  added  to  arti- 
ficial butter  in  Germany  in  order  to  be  able  to  detect  the  same  (see  Furol) . 
Its  bromine  and  iodine  addition  products  are  used  in  medicine  as  bromipin 
and  iodipin. 

Soaps.  On  heating  glycerides  with  alkali  hydroxides,  and  other 
strong  bases  they  are  decomposed  in  a  manner  similar  to  the 
esters  of  the  mono-  and  dihydric  alcohols,  i.e.,  they  decompose  into 
salts  of  the  acids  contained  in  the  glycerides  and  into  glycerine 
(p.  432).  The  decomposition  of  the  esters,  i.e.,  the  fats,  by  means 
of  caustic  alkalies  is  called  saponification  (p.  357,  2).  Soaps  are  the 
alkah  salts  of  palmitic,  stearic,  and  oleic  acids.  Sodium  soaps  are 
hard,  while  the  potassium  soaps  are  soft. 

The  soaps  are  soluble  in  water  and  alcohol,  but  insoluble  in  common 
salt  solutions  ("salting  out"  of  soaps  is  the  separation  of  the  soaps  from 
the  sticky  substances  formed  in  the  saponification).  The  soaps  have  a 
solvent  action  on  bodies  otherwise  insoluble  in  water,  such  as  hydrocar- 
bons, resins,  phenols,  fats,  etc.     By  the  action  of  large  quantities  of  water 


SOAPS.  437 

the  soaps  are  in  part  decomposed  into  free  alkali  and  acid  salts  of  the  fatty 
acids.  The  action  of  soaps  in  washing  depends  upon  this  property,  as 
the  alkali  set  free  and  the  acid  salt  of  the  fatty  acids  which  form  the 
froth  readily  remove  the  fat  in  the  form  of  an  emulsion,  and  the  froth 
envelops  the  dirt  and  removes  it. 

The  other  salts  of  the  above-mentioned  fatty  acids  are  mostly  soluble 
in  alcohol  but  insoluble  in  water,  hence  water  rich  in  calcium  salts  forms 
a  precipitate  with  soap  solutions  forming  insoluble  calcium  salts  of  the 
fatty  acids  which  is  the  reason  why  hard  waters  are  not  suitable  for  wash- 
ing purposes. 

Official  soap  is  pure  sodium  soap;  Green  soap  is  pure  potassium  soap, 
whose  alcoholic  solution  is  called  spiritus  saponatus. 

Soap  liniment,  opodeldoc,  is  a  gelatinous  mixture  of  alcohol,  sodium 
soap,  camphor,  ammonia,  and  ethereal  oils;  liquid  opodeldoc  is  a  solution 
of  potassium  soaps  and  camphof  in  alcohol.  Ammonia  liniment  is  a  mixture 
of  fatty  oils  with  ammonia,  and  in  the  presence  of  camphor-oil  it  is  called 
camphorated  ammonia  liniment. 

Plasters.  The  lead  salts  of  the  fatty  acids  are  called  lead  plasters. 
These  are  obtained  directly  by  boiling  fats  with  lead  oxide  and  water 
(p.  432). 

On  mixing  lead  plaster  with  different  substances  we  obtain  mercurial 
plaster,  soap  plaster,  adhesive  plaster,  etc.  The  tough  mixtures  of 
resins,  wax,  and  oils  with  active  bodies  which  are  used  externally  are  also 
called  plasters.      These  differ  from  the  salves  only  in  their  consistency. 

Salves  are  the  semi-plastic  mixtures  of  fats  or  oils  with  wax,  resin, 
etc.,  which  have  either  solid  bodies  as  powders  or  solutions  mixed 
therewith. 

Emulsions.  If  water  contains  bodies,  such  as  plant  mucilage,  albu- 
min, gums,  etc.,  in  solution,  they  give  a  mucilaginous  character  and 
greater  viscosity  to  the  liquid  If  oils  are  thoroughly  mixed  with  such 
liquids,  they  remain  suspended  as  very  small  globules  and  the  liquid  retains 
a  milky  appearance.     Such  mixtures  are  called  emulsions. 


4.  Monohydric  Compounds  of  Trivalent  Alcohol  Radicals. 

Trihydric  alcohol  radicals  may  also  appear  monovalent,  but  not  free, 
and  form  unsaturated  compounds  which  have  the  property,  like  all 
other  unsaturated  compounds,  of  readily  taking  up  2  atoms  of  H,  Br, 
etc.,  and  being  converted  into  saturated  compounds.  The  radical 
C^H,  or  CH^^CH-  is  called  vinyl,  C3H5  or  CH^^CH-CHj-  is  called 
allyl,  etc. 

a.  Alcohols,  etc. 

Vinyl  alcohol,  C2H3-OH  or  CHa^CHOH,  occurs  in  commercial  ether 
and  is  very  unstable. 

Vinyl  sulphide,  C2H3-S-C2H3,  found  in  the  ethereal  oil  of  garlic,  is  a 
colorless  liquid  having  a  garlic-like  odor  and  boils  at  101°. 


438  ORGANIC  CHEMISTRY, 

Neurine,  trimethylvinylammonium  hydroxide,  (CH3)3N(C2H3)OH,  has 
been  treated  of  on  page  380. 

Allyl  iodide,  C.HJ  or  CH2=CH-CH2-I,  is  obtained  on  the  distillation 
of  phosphorus  iodide  with  glycerine :  C3H5(OH)3  +  PI, =C3H5l  +  H.POg  +  21. 
It  is  a  colorless  hquid  having  a  mustard-like  odor",  and  from  which  the 
various  allyl  esters  can  be  obtained  by  heating  with  the  silver  salts. 

Allyl  sulphide,  (€3115)28,  as  well  as  allyl  disulphides,  for  example, 
allyl  propyl  disulphide,  C3H5-  S-S-Q^H^,  forms  the  chief  constituent  of  the 
ethereal  oil  of  the  onion,  garlic,  asafcttida,  etc. 

Allyl  Isosulphocyanic  Ester,  CgHs'NCS,  Allyl  Mustard-oil, 
Mustard -oil. 

Preparation.  1.  Ordinarily  by  allowing  powdered  black  mustard- 
seeds  (Sinapsis  nigra)  to  stand  in  contact  with  water,  when  the  con- 
tained glucoside  sinigrin  (also  called  potassium  myronate)  is  split  by 
the  action  of  the  ferment  myrosin  contained  therein  into  allyl  iso- 
sulphocyanic ester,  potassium  hydrosulphate,  and  glucose.  The 
allyl  isosulphocyanic  ester  can  be  separated  by  distillation: 

C,oHieNS209K+  HOH  =  C3H5-NCS4-  KHSO,+  CeH^.Oe. 

2.  By  the  action  of  carbon  disulphide  upon  allylamine 

CS2  +  NH2-C3H5  =  C3H5-NCS  +  H2S. 

3.  By  heating  allyl  iodide  with  potassium  sulphocyanide  (see  below). 

Properties.  Colorless  liquid  boiling  at  148-152°,  having  an  ex- 
tremely pungent  odor  and  producing  blisters  when  applied  to  the  skin. 
It  is  slightly  soluble  in  water  but  readily  soluble  in  alcohol  (Spiritus 
sinapis). 

Allyl  sulphocyan,  CyHp-SCN,  is  obtained  from  allyl  iodide  by  the  action 
of  potassium  sulphocyanide  in  the  cold: 

NCSK  +  C3H5I = NCS-  C3H5  +  KI. 

It  is  a  liquid  having  a  leek-like  odor  and  boiling  at  161°,  and  undergoing 
a  molecular  rearrangement  into  allyl  mustard-oil  on  warming: 

N-(>S(C3H5)  =S=C=N-(C3H5). 

Allyl  sulphocyan.     Allyl  isosulphocyanic  ester. 

Allyl  Alcohol,  C3H5-OH  or  CH^-CH-CH^-OH.  Preparation. 
Obtained  on  gradually  heating  glycerine  with  oxalic  acid  to  260°,  when 
the  oxalic  acid  is  split  into  CO2  and  formic  acid  (p.  352),  and  this  latter 
body  forming  with  the  glycerine  at  190°  its  monoformic  acid 


ALLYL  COMPOUNDS.  439 

which  on  distillation  decomposes  into  ally!  alcohol,  carbon  dioxide, 
and  water: 

H  •  COO-C3H5(OH)2  =  C3HrOH+  H,0+  CO,. 

2.  From  the  allyl  esters  obtained  from  ally]  iodide  by  heating  with 
caustic  alkali. 

3.  By  the  action  of  nascent  hydrogen  upon  allyl  aldehyde. 

Properties.  Colorless  liquid  boiling  at  97°,  having  a  pungent 
odor  and  which  on  oxidation  with  silver  oxide  yields  allyl  aldehyde 
and  then  the  corresponding  acrylic  acid  (p.  440). 

Allyl  Aldehyde,  CgH.O  or  CH2=CH-CH0,  Acrolein.  Prepara- 
tion. By  the  moderate  oxidation  of  allyl  alcohol  and  by  strongly 
heating  glycerine  or  fats: 

C3H5(OH)3  =C3H,0+2Hp. 

The  decomposition  of  glycerine  takes  place  completely  if  it  is  heated 
with  dehydrating  substances,  such  as  phosphoric  anhydride  or  potas- 
sium bisulphate. 

Properties.  Colorless  liquid  boiling  at  52°  and  having  an  unpleas- 
ant pungent  odor  which  causes  irritation  of  the  mucous  membranes. 
It  is  not  readily  soluble  in  water.  The  odor  of  burnt  fats  as  well 
as  of  the  smouldering  tallow  candle  is  due  to  acrolein.  On  keeping, 
acrolein  undergoes  polymerization  and  is  converted  into  amorphous 
white  disacryl  or  metacrolein.  On  oxidation  it  yields  acrylic  acid, 
C3H4O2,  the  first  member  of  the  following  series  of  acids : 

Citronellol,  CjoHig-QH,  an  homologous  alcohol  of  allyl  alcohol  and  its 
aldehyde,  and 

Citronellal,  CjoHigO,  are  found  in  many  etheral  oils  (p.  445). 

h.  Oleic  acid  series. 
General  formula  CNH2N-2O2. 

A  series  of  monobasic,  unsaturated  acids  are  derived  from  allyl 
alcohol  and  its  little-known  homologues.  These  acids  are  obtained 
by  the  oxidation  of  the  corresponding  alcohol  and  aldehyde  or  by 
treating  the  monohalogen  derivatives  of  the  fatty  acids  with  alco- 
holic caustic  alkali: 

CgHsaOj    +     KOH     =     CgH.O^     +    KCl+H^O. 

Chlorpropionic  acid.  Acrylic  acid. 


440  ORGANIC  CHEMISTRY, 

They  are  very  similar  to  the  fatty  acids,  but  differ  from  these 
especially  by  the  power  they  have  of  taking  up  hydrogen  or  halogens 
by  addition  and  thus  being  transformed  into  fatty  acids  or  their 
substitution  products: 

CHrCH-COOH+  Hj  =  CH3-CH2-COOH; 

Acrylic  acid.  Propionic  acid. 

CHrCH-COOH+  Br^  =  CH^Br-CHBr-COOH. 

Fats  which  contain  glycerides  of  the  oleic  acid  series  and  other  unsatu- 
rated acids  on  standing  with  an  alcoholic  solution  of  iodine  and  mercuric 
chloride  form  addition  products.  From  the  amount  of  combined  iodine, 
which  can  be  readily  estimated,  we  can  determine  in  a  fat  the  proportion 
of  unsaturated  glycerides  to  the  saturated  glycerides,  which  do  not  com- 
bine with  the  iodine  (Hiibl's  iodine  equivalent).  "We  thus  obtain  a  knowl- 
edge of  the  nature  of  the  fat  and  whether  it  is  adulterated  with  other 
fats. 

From  crotonic  acid  upward  we  have  two  stereoisomers  (p.  308c)  besides 
the  structural  isomers. 

Acrylic  acid,  C3H4O2,  is  produced  on  warming  a  watery  solution  of 
acrolein  with  silver  oxide.  The  silver  separates  as  a  minor  (p.  350),  and 
at  the  same  time  silver  acrylate  is  produced,  from  which  the  acid  can  be 
set  free  by  HjS.     It  is  a  pungent  acid  liquid  boiling  at  140°. 

Crotonic  acids,  CJlf),,,  form  three  fluids  and  one  solid  body.  Two 
of  them  are  stereoismers  and  occur  in  crude  wood  alcohol,  the  third  in 
ethereal  camomile-oil.  The  acids  were  incorrectly  considered  as  con- 
stituents of  croton-oil   (p.  436). 

Angelic  acid,  CgH^Og,  occurs  free  with  valerianic  acid  in  the  angelica 
root  and  as  butyl  and  amyl  ester  in  Roman  camomile-oil. 

Tiglic  acid,  C5H3O2,  occurs  as  a  glyceride  in  croton-oil  and  Roman 
camomile  oil,  and  is  a  stereoisomer  of  angelic  acid. 

Hypogaeic  acid,  CjgH3302,  as  glyceride  in  the  oil  of  the  earth-nut  (p.  377) 
and  in  whale-oil.     It  forms  colorless  crystals. 

Oleic  acid,  C,jjH.^^O^,  elaeic  acid,  occurs  as  glyceride  in  most  fats  and 
forms  the  chief  constituent  of  the  non-drying  oils.  It  is  obtained  in 
the  manufacture  of  stearine  candles,  where  the  free  fatty  acids  (p.  432), 
which  form  a  semi-solid  mass,  are  pressed  between  warm  plates,  whereby 
the  liquid  oleic  acid  is  pressed  out,  while  the  remaining  solid  palmitic 
and  stearic  acids  are  moulded  into  candles.  It  is  a  colorless  oily  liquid 
which  does  not  redden  litmus  and  crystallizes  at  4°,  and  which  oxidizes 
in  the  air,  turning  yellow  and  rancid.  By  nitrous  acid  it  is  converted 
into  its  crystalline  stereoisomer. 

Elaidic  acid,  Ci^Hg^O^,  which  melts  at  45°  (detection  of  non-drying  oils, 
see  liinoleic  Acid). 

Lead  oleatCj  Pb(C,sH,,02)2,  is  soluble  in  ether  (separation  of  oleic  acid 
from  stearic  and  palmitic  acids). 

Sodium  oJeatCf  eunatrol,  is  a  fine  white  powder  which  is  used  in  medi- 
cine. 

Rapinic  acid,  CigHg^Oa,  occurs  as  a  glyceride  in  rape-seed  oil 


TETRAVALENT  ALCOHOL  RADICALS,  441 

Erucic  acid,  C22H42O2,  exists  as  glyceride  in  the  fatty  oils  of  the  varie- 
ties of  Eruea,  Brassica,  and  Sinapis,  and  forms  colorless  crystals  which 
are  transformed  into 

Brassidic  acid,  0231142^2;  when  treated  with  nitrous  acid.  It  is  the 
stereoisomer  of  eracic  acid. 

Acids  closely  related  to  the  Oleic  Acid  Series. 

Ricinoleic  acid,  CigHg^Os,  oxyoleic  acid,  is  a  thick  oily  liquid  which 
occurs  as  a  glyceride  in  castor-oil.  Nitrous  acid  converts  it  into  its  stereo- 
isomer, 

Ricinelaidic  acid,  0,5113403,  which  forms  the  Turkey-red  oil  of  the 
dyer  which  consists  of  ricinoleic  sulphuric  acid  (OisHagOa)"!!^©^. 

COMPOUNDS  OF  TETRAVALENT  ALCOHOL  RADICALS. 
I.  Tetravalent  Alcohol  Radicals. 

General  formula  On    2n-2- 

Acetylene       CgHg  Gas  Valerylene  CgHg    Liquid 

AUylene  OgH^  Gas  Hexoylene    OgHjo  Liquid 

Crotonylene   O^Hg  Liquid  etc. 

These  radicals  are  also  called  ethin,  propin,  butin,  pentin,  etc. 
They  are,  like  the  divalent  radicals,  known  in  the  free  state.  They  are 
obtained  by  heating  the  alkylene  halogen  compounds  CnH2nX2  with 
alcoholic  caustic  alkah: 

C^H.Br^-t-  2K0H  =  C,H,+  2KBr-f  2HO2. 

They  combine  directly  with  the  halogens  or  with  nascent  hydrogen, 
forming  saturated  compounds. 

In  the  isomers  of  this  series,  which,  like  acetylene,  contain  the  -OH 
group,  this  hydrogen  can  be  replaced  by  metals.  Mineral  acids  develop 
from  these  metallic  compounds  the  pure  hydrocarbon  OnH2n-2  (for  method 
of  preparation  see  Acetylene). 

Acetylene,  ethin,  C2H2  or  CH=CH. 

Formation.  1.  It  is  the  only  hydrocarbon  with  the  exception 
of  methane  and  ethane  which  can  be  prepared  by  the  direct  union 
of  its  elements,  as  by  passing  hydrogen  through  a  vessel  containing 
two  carbon  poles  between  which  the  electric  arc  is  playing. 

2.  It  is  also  formed  in  the  incomplete  combustion  (by  passing  the 
vapors  through  red-hot  tubes)  of  many  carbon  compounds  (such  as 
alcohol,  ether,  methane,  ethylene) ,  and  hence  is  also  found  in  illuminat- 
ing-gas. From  this  latter  it  can  be  obtained  in  large  quantities  by 
allowing  the  Bunsen  flame  to  retreat  in  the  burner. 


442  ORGANIC  CHEMISTRY, 

3.  It  is  also  produced  in  the  electrolysis  of  alkali  salts  of  fumaric  and 
maleic  acid  (see  p.  421), 

KOOC-C2H2-COOK  =  HC^CH  +  2CO2 + 2K, 

Potassium  fumarate.         Acetylene. 

as  well  as  from  bromoform  or  iodoform  on  heating  with  powdered  silver: 
2CHl3+6Ag=6AgH-C2H,. 

Preparation.  From  calcium  carbide  (p.  223)  by  decomposition 
with  water:    CaC2+2HOH  =  Ca(OH)2+C2H2. 

Properties.  Penetrating,  colorless,  poisonous  gas  soluble  in  equal 
volumes  of  water  and  very  readily  soluble  in  acetone  {^^  part). 
It  burns  with  a  strongly  illuminating  and  smoky  flame  and  is  liquefied 
at  0°  and  26  atmospheres  pressure.  Decomposes  into  its  elements 
with  explosion  when  ignited  by  mercury  fulminate.  If  acetylene 
is  slowly  passed  through  a  faint  red-hot  tube,  it  is  converted  into 
benzene,  CgHe,  the  most  important  compound  of  the  isocarbocyclic 
group : 

3C2H2  =  CgHe. 

The  use  of  burning  acetylene,  with  its  intensely  illuminating  flame,  in 
illumination  has  the  advantage  that  it  can  be  very  readily  produced  from 
calcium  carbide  at  the  locality  where  it  is  to  be  used.  On  the  other  hand 
it  has  the  disadvantage  that  the  explosion  limit  of  a  mixture  of  air  with 
acetylene  lies  very  much  farther  apart  than  with  illuminating-gas. 

Air  with  3  to  65  per  cent,  acetylene  explodes  in  contact  with  a  flame. 

Liquid  acetylene,  as  well  as  the  gas  under  a  pressure  of  2  atmospheres, 
is  decomposable  with  violent  explosion.  Acetylene  obtained  from  calcium 
carbide  contains  HgS,  PHg,  and  often  P2H4,  which  makes  it  spontaneously- 
inflammable  (p.  166).  Infusorial  earth  impregnated  with  chromic  acid- 
sulphuric  acid  (heratol),  cuprous  chloride-hydrochloric  acid  (frankolin), 
or  a  mixture  of  chloride  of  lime  with  lead  chromate  (akagin),  or  porous 
pieces  of  chloride  of  lime  (puratylen)  serve  to  purify  acetylene  used  for 
illuminating  purposes. 

In  order  to  prepare  chemically  pure  acetylene  the  gases  containing  the 
acetylene  are  passed  into  a  solution  of  silver  nitrate  (see  Metallic  Deriva- 
tives). 

Metallic  derivatives  of  acetylene.  Acetylene  precipitates  red  explo- 
sive cuproacetylene,  CaCug  +  HgO,  from  an  ammomacal  cuprous  chloride 
solution,  and  also  white  explosive  acetylene  silver,  CjAgg  +  HgO,  from  an 
ammoniacal  silver  nitrate  solution.  Acids  evolve  pure  acetylene  from 
these  compounds :  CgCug  +  2HC1 = CgHg  +  2CuCl.  If  sodium  is  heated  with 
acetylene  gas,  sodium  acet}^lene,  CgHNa  and  CgNag,  are  obtained  as  a  black 
powder,  which  with  water  is  converted  into  acetylene  and  NaOH: 

C2HNa+H20=C2H2+NaOH  (see  Carbides). 


TETRAHYDRIC  ALCOHOLS,  443 


2.  Tetrahydric  Alcohols. 

General  formula  CnH2n-2(OH)4. 

These  have  two  asymmetric  C  atoms  and  hence,  like  their  derivatives, 
two  different  stereoisomeric  modifications  are  possible. 

Erythrite,  phycite,  HOH2C-CH(OH)-CH(OH)-CH20H  or  C,He(OH)„ 
is  the  only  tetrahydric  alcohol  occurring  in  nature,  and  is  found  free  in 
the  Protococcus  vulgaris,  and  as  an  ester  erythrin  (which  see)  in  several 
algse  and  lichens.  It  can  be  obtained  from  these  by  caustic  alkali.  It 
forms  large,  optically  inactive  crystals  readily  soluble  in  water,  but  with 
difficulty  in  alcohol,  and  has  a  sweet  taste  like  all  the  polyhydric  alcohols. 
On  warming  with  HI  it  is  reduced  to  secondary  butyl  iodide:  C^HeCOH)^^- 
7HI=C4Hgl  +  4H20  +  6I,  and  on  oxidation  it  yields  like  all  polyhydric 
alcohols  mixed  compounds  (p.  337).  Nitro-sulphuric  acid  converts  it 
into  the  explosive  erythrin  nitrate,  C4H6(N03)4. 

3.  Derivatives  of  Tetrahydric  Alcohols. 

Erythrose,  C^H,0,  or  H0H2C-CH(0H)-CH(0H)-CH0,  is  obtained 
on  the  careful  oxidation  of  erythrite,  and  as  an  aldose  is  a  carbohydrate 
(p.  447),  but  it  is  unfermentable  and  forms  a  colorless  sweet  sirup. 

Erythritic  acid,  H0H2C-(H0)HC-CH(0H)-C00H  or  C^HgOs,  trioxy- 
butyric  acid,  is  obtained  in  the  moderate  oxidation  of  erythrite  and  laevu- 
lose,  and  forms  colorless  deliquescent  crystals. 

Mesotartaric  acid,  HOOC-(HO)HC-CH(OH)-COOH  or  C^B.^0^  (p. 
428),  is  the  next  product  on  the  oxidation  of  erythrite. 

Dioxytartaric  acid,  HOOC-CO-CQ-COOH,  theoreticaUv  the  final 
oxidation  product  of  erythrite,  has  thus  far  been  obtained  only  indirectly 
from  tartaric  acid  and  always  as  C4H2O6  +  2H2O;  hence  it  has  received  the 
name  dioxytartaric  acid,  C^HeOg  (p.  428). 

COMPOUNDS  OF  PENTAVALENT  ALCOHOL  RADICALS. 

I.  Pentavalent  Alcohol  Radicals. 

General  formula  CnH2n-3- 
In  common  with  all  the  radicals  with  uneven  valence  they  are  Utt- 
known  in  the  free  state. 

2.  Pentahydric  Alcohols. 

General  formula  CnH2n-3(OH)5. 

These  have  two  asymmetric  C  atoms,  and  therefore  they  exist,  like  their 
derivatives  in  two  stereoisomeric  modifications  (p.  306).  They  form  crys- 
tals having  a  sweet  taste,  and  are  readilv  soluble  in  water.  They  are 
obtained  from  their  aldehydes  or  ketones  by  the  action  of  nascent  hydro- 
gen. 

Arabite,  C,B.,^0^  or  CH20H-(CHOH)3-CH20H,  is  inactive. 

Adonite,  CgHjaOg,  the  stereoisomer  of  arabite,  occurs  in  the  Adonis 
vernalis,  is  inactive,  and  is  obtained  from  ribose  (p.  444). 

Xylite,  CsHjjOg,  stereoisomer  of  arabite,  is  inactive. 

Rhamnite,  CoHi^O,  or  C5H6(OH)5(CH3),  is  dextrorotatory. 


444  ORGANIC  CHEMISTRY. 

3.  Derivatives  of  Pentahydric  Alcohols. 

The  aldoses  and  ketoses,  C5H10O5  or  CH0(CH0H)3CH,0H,  and 
CH20H-CO-(CHOH)2CH20H,  derived  from  the  alcohols  C^Hj^Os,  are  car- 
bohydrates (p.  447),  but  unfermentable,  and  are  called  ^pentoses.  They 
form  colorless,  very  sweet  crystals  which  on  heating  with  dilute  mineral 
acids  yield  furol,  C5Hio06=3HOH+C5H402,  which  is  used  in  their  quan- 
titative estimation  and  detection  from  other  carbohydrates.  They  are 
known,  like  their  alcohols,  in  numerous  stereoisomeric  modifications. 
They  occur  in  the  plants  as  so-called  pentosanes,  CgHgO^,  which  on  warm- 
ing with  dilute  acids  are  converted  into  pentoses  by  taking  up  water. 

The  following  pentoses  are  aldoses: 

Arabinose,  C5H10O5,  gum-sugar,  is  obtained  from  its  pentosane  araban 
on  boiling  cherry  gum,  gum  arable,  or  sugar-beets  with  dilute  acids.  It 
is  dextrorotatory.  Inactive  arabinose  (urine  pentose)  occurs  sometimes 
in  the  urine. 

Xylose,  CgHjoOs,  wood  sugar,  is  produced  from  most  woods,  leaves, 
bark,  etc.,  by  the  action  of  boihng  dilute  acids  upon  the  pentosane  xylan 
(wood  gum).     Xylose  is  dextrorotatory. 

Ribose,  CgHioOg,  obtained  synthetically,  is  optically  inactive. 

Lyxose,  C5H,o05,  is  Isevorotatory  and  is  obtained  synthetically. 

Rhamnose,  C5H9(CH3)05,  isodulcite,  methyl  pentose,  is  obtained  from 
certain  glucosides.  It  is  dextrorotatory.  Other  methyl  pentoses  are  called 
fucose  and  quinovose. 

Arabonic  acid,  xylonic  acid,  ribonic  acid,  and  lyxonic  acid,  CgHioOj 
or  HOH2C~(CH'OH)3COOH,  are  the  stereoisomeric  acids  corresponding 
to  the  above  aldehydes.     They  form  colorless  crystals. 

Trioxyglutaric  acids,  C,Usb^  or  H00C(CH0H)3C00H,  is  produced  on 
the  further  oxidation  of  the  above  aldehydes.  Four  stereoisomers  are 
known. 

Saccharonic  acids,  C.TL^^O,  or  HOH2C-CH2-(CHOH)3-COOH.  Of 
these  pentavalent  monobasic  acids  three  are  known.  They  are  produced 
by  the  action  of  Ca(0H)2  upon  the  carbohydrates  galactose,  glucose, 
Isevulose  (p.  449).  They  are  unstable  and  quickl}^  change  into  their  inter- 
nal anhydrides  (lactones),  the  saccharons,  CgHjoOc.  (This  must  not  be 
confounded  with  the  sweet  substance  called  saccharin.) 

4.  Monohydric  Compounds  of  Pentavalent  Alcohol  Radicals. 

As  unsaturated  monohydric  alcohols,  etc.,  can  be  derived  from  vinyl, 
C2H3,  allyl,  C3H5,  and  their  homologues  (p.  437),  so  also  we  may  have  the 
same  from  propargyl,  C3H3,  and  its  homologues. 

a.  Alcohols,  etc. 

Propargyl  alcohol,  C3H3-OH  or  HC^O-CHjOH,  is  synthetically  ob- 
tained as  a  colorless  liquid  boiling  at  114°. 

Linalool,  C|oH,7-OH  is  an  optically  active  tertiary  alcohol;  with 
dilute  acids  it  is  converted  into  its  isomer, 

Geraniol,  CjoH^yOH,  rhodinol,  which  is  an  optically  active  primary 
alcohol  and  the  ch  ef  constituent  of  rose-oil.  On  oxidation  it  is  con- 
verted into  its  aldehyde, 

Geranial,  CjoHj^O,  citral,  the  odoriferous  substance  of  oil  of  lemons. 

These  compounds  are  colorless  liquids  and  occur  singly  or  together, 


HEXAVALENT  ALCOHOL  RADICALS.  445 

often  also  mixed  with  citronellal  and  citronellol  (p.  439),  in  many  plants 
or  their  ethereal  oils;  thus  in  oil  of  balm-mint,  citronella,  geranium,  rose, 
lavender,  lemon,  linaloe,  etc.  As  they  are  isomeric  with  certain  terpenes, 
and,  like  the  olefines,  have  a  double  bondage  of  the  C  atoms,  they  are  also 
called  olefinic  terpenes.  Linalool  and  geraniol  are  readily  trans- 
formed into  terpinhydrate,  CjoHajOg  +  B./),  which  can  readily  be  obtained 
from  the  pinenes,  which  explains  the  simultaneous  presence  of  these  two 
fatty  bodies  with  terpenes  in  many  plants. 

b.  Pwpiolic  Acid  Series. 

The  acids  of  this  series  have  the  general  formula  CNH2N-4O2,  and  may 
have  either  a  treble  or  two  double  bonds  in  the  molecule:  HC^OCOOH, 
propiolic  acid,  C2H4-CH-CH-CH-COOH,  sorbinic  acid.  They  are  pro- 
duced from  the  sodium  compounds  of  acetylene  by  the  action  of  GOg  and 
are  very  similar  to  oleic  acids,  and  may  be  converted  into  them  by  nascent 
hydrogen,  and  then  into  fatty  acids. 


Propiolic  acid,  CgHjOj,  propargylic  acid,  and 
Tetrolic  acid,    C^H^Oa,  are  obtain 


obtained  synthetically. 
Sorbinic  acid,  C-HgOj,  occurs  in  the  unripe  fruit  of  the  mountain-ash. 
Geranic  acid,  CioHj.02,  obtained  by  oxidizing  geranial, 
Linoleic  acid,    C10H3.O2,  occurs  as  glycerid  as  chief  constituent  of  drying 
oils,  and  is  a  yellowish  oil  which  is  not  changed  by  nitrous  acid.      (Hence 
if  a  non-drying  oil  does  not  become  solid  with  nitrous  acid  it  must  be  a 
mixture  of  some  drying  oil.) 

COMPOUNDS  OF  HEXAVALENT  ALCOHOL  RADICALS. 
I.  liexavalent  Alcohol  Radicals. 

General  formula  CnH2n-4. 

Valylene,  C5H-,  obtained  from  C,H8Br2  by  alcoholic  caustic  alkali 
(p.  348  4),  as  well  as  by  distilling  Cannel  coal.  It  is  a  liquid  boiling  at 
50°  and  having  a  leek-like  odor. 

2.  Hexahydric  Alcohols. 

General  formula  CnH2n -4  (0H)6. 

There  bodies  have  4  asymmetric  C  atoms,  and  hence  they  occur  in 
numerous  stereoisomeric  modifications  (p.  306).  These  alcohols  and 
their  derivatives  are  generally  obtained  synthetically.  In  the  following 
only  those  alcohols  occurring  in  nature  will  be  discussed. 

Mannit5,  CeHj^Oe  or  CH20H-(CH-OH),-CH20H,  is  widely  distrib- 
uted in  plants,  especially  m  the  larch  and  manna-ash  (whose  dried 
juice  is  called  manna),  in  celery,  sugar-cane,  oyster- plant,  quitch-grass, 
olives,  etc.,  as  well  as  in  normal  dog  urine.  It  is  obtained  from  manna  by 
boiling  with  alcohol  and  evaporating  the  solution  to  crystallization.  It 
is  also  produced  in  the  mucilaginous  fermentation  of  sugars  and  by 
the  action  of  nascent  hydrogen  upon  the  aldehyde  alcohols,  mannose 
and  glucose.  It  forms  white,  sweet,  dextrorotatory  needles  which  are 
readily  soluble  in  water  and  alcohol  and  which  on  oxidation  yield  man- 
nose,  CjHjgOe,  then  mannonic  acid,  CjHijOy,  and  finally  mannosaccharic 


446  ORGANIC  CHEMISTRY, 

acid,  CjHjoOg.  Nitro-sulphuric  acid  converts  it  into  the  explosive  man- 
nite  nitrate,  C5Hg(N03)8. 

Dulcite,  melampyrite,  CgHj^Og,  stereoisomer  of  mannite  occurs,  in  the 
Madagascar  manna,  in  varieties  of  Melampyrum,  Scrophularia,  Evony- 
mus,  Rhinantus.  It  forms  colorless  prisms  which  are  less  soluble  in  water 
than  mannite  and  nearly  insoluble  in  alcohol.  It  may  be  artificially  pre- 
pared by  the  action  of  nascent  hydrogen  upon  its  aldehyde  alcohol, 
galactose,  CgKLaO.,  as  well  as  from  milk-sugar.  On  oxidation  it  yields 
mucic  acid,  Gf^li^^O^,  then  racemic  acid,  C^HgOg.  Dulcite  is  the  only  poly- 
hydric  alcohol  which  reduces  alkaline  solutions  of  copper  oxide.  Because 
of  its  configuration,  which  is  similar  to  mesotartaric  acid  (p  307),  it  is 
inactive  and  cannot  be  split  into  active  modifications. 

Sorbite,  CgHj^Og,  stereoisomer  of  mannite,  occurs  in  the  mountain-ash 
and  the  fruit  of  many  Rosaceae.  It  is  produced  by  the  action  of  nascent 
hydrogen  upon  its  ketone  alcohols  sorbinose  and  laevulose,  or  upon  its  alde- 
hyde alcohol  glucose.  It  forms  small  dextrorotatory  crystals  with  J  mol. 
HgO,  and  on  oxidation  it  yields  glucose,  CgHj20g,  then  gluconic  acid, 
CgH^gUr,  and  finally  saccharic  acid,  CjH^oOg. 

3.  Derivatives  of  Hexahydric  Alcohols. 

Mannose,  glucose,  galactcose,  H0H20-(CH0H)<-CH0  or  CgHijOe,  are 
the  three  stereoisomeric  aldehyde  alcohols  of  the  above-mentioned  hexa- 
hydric alcohols  (see  Carbohydrates). 

Laevulose  and  sorbinose,  CH20H-(CHOH)3-CO-CH20H  or  CeHj^O,, 
are  the  two  stereoisomeric  ketone-alcohols  of  the  above-mentioned  hexa- 
hydric alcohols  (see  Carbohydrates). 

These  aldoses  and  ketoses,  CjHjgOe,  and  their  anhydride  condensation 
products  form  the  most  important  compounds  of  the  carbohydrate  group 
(p.  451) 

Mannonic,  gluconic,  galactonic  acids,  CgH^^^y  or  HOH20-(CH-OH)4- 
COOH.  These  three  stereoisomeric  hexon  acids  are  obtained  on  the  oxi- 
dation of  mannose,  glucose,  galactose  with  chlorine-  or  bromine- water. 
Their  lactones  (p.  404,  a),  yield  the  above-mentioned  carbohydrates  on 
reduction. 

Glycuronic  acid,  CeH^O^  or  OHC-(CHOH,)-COOH,  stands  between 
mannonic  and  saccharic  acids.  It  is  found  in  the  urine  after  partaking 
of  various  substances,  such  as  camphor,  chloral,  naphthalene,  turpentine, 
combined  with  these  bodies,  and  can  be  obtained  from  these  combina- 
tions by  treatment  with  acids,  or  can  be  obtained  by  the  reduction  of 
dextrosaccharic  acid  (see  below).  Glycuronic  acid  is  a  sirup  which  is 
readily  soluble  in  water  and  alcohol  and  dextrorotatory,  while  the  con- 
jugated glycuronic  acids  are  laevorotatory.  It  occurs  in  the  artist  pig- 
ment Indian  yellow,  in  the  form  of  magnesium  euxanthinate,  which  splits 
by  HCl  into  euxanthic  acid,  C,yH,j,Oi,,  which  in  turn  decomposes  at  125° 
into  euxanthon,  CjaH^O^.  and  glycuronic  acid,  CeHj^Oy. 

Saccharic  acid,  CgHi^Os  or  HOOC-(CHOH),-COOH,  stereoisomeric 
mannosaccharic  acid,  is  produced  in  the  oxidation  of  cane-sugar,  glucose, 
starch,  or  mannite,  by  means  of  nitric  acid.  It  forms  deliquescent 
gummy  masses  which  yield  tartaric  acid  on  further  oxidation.  The  dex- 
tro-  or  laevosaccharic  acid  is  obtained  according  to  the  material  we  start 
from,  and  these  unite,  forming  the  inactive  modification. 


CARBOHYDRATES.  447 

Mucic  acid,  CgH,oOg,  stereoisomer  of  saccharic  acid,  is  obtained  on  the 
oxidation  of  dulcite,  galactose,  plant  mucilages,  and  certain  varieties  of 
gums  by  nitric  acid.  It  forms  a  white  crystalline  powder  nearly  insoluble 
in  water,  which  on  further  oxidation  yields  racemic  acid,  C^HgOj.  It  is 
optically  inactive  and  does  not  split  into  active  modifications. 

COMPOUNDS    OF   HEPTAVALENT  AND    HIGHER  ALCOHOL 
RADICALS. 

I.  Alcohol  Radicals. 

A  few  of  these  with  even  valence  are  known;  e.g.,  diacetylene,  CJi^, 
also  dipropargyl,  and  dimethyl  acetylene,  CgHg,  both  isomers  of  benzene. 

2.  Alcohols  and  their  Derivatives. 

Perseit,  CyHjgOy  or  C7H9(OH)7,  is  contained  in  the  fruit  of  the  Launis 
Persea.     It  forms  colorless  crystals  which  melt  at  188°. 

Volemite,  C^il^^O^,  found  in  the  Lactarius  volemus,  forms  colorless 
dextrorotatory  needles  which  melt  at  150°, 

Volemose,  CyHj^O^,  is  the  aldehyde  of  volemite. 

Glucoheptite,  C^H^gO^  or  C7H9(OH)7,  glucooctite,  QH^sOs  or  C8H,o(OH)8 
glucononite,  CgligoOg  or  C9H,j(0H)g.  These  alcohols  form  colorless  crys- 
tals and  are  produced  by  the  action  of  nascent  hydrogen  upon  their  alde- 
hyde alcohols 

Glucoheptose,  C7H,p„  glucooctose,  C«HigO^,  glucononose,  CgHj^g, 
are  synthetically  prepared  from  the  hexoses  CgHiaOg  (p.  451,  4)  and  yield 

Glucoheptonic  acid,  CjU^^O^,  glucooctonic  acid,  CsHjgOg,  and  gluco- 
nonic  acid,  (VHisO.„,  on  oxidation.  They  may  also  be  prepared  from 
the  glucoses,  CgHjgOg,  by  the  addition  of  hydrocyanic  acid,  as  mentioned 
on  p.  451,  4. 

CARBOHYDRATES. 

The  name  carbohdyrate  depends  upon  the  fact  that  all  these 
compounds  contain  hydrogen  and  oxygen  in  the  same  proportion 
as  they  exist  in  water,  but  this  proportion  also  exists  in  many  other 
compounds,  hence  it  is  not  characteristic  of  the  carbohydrates. 

In  the  broad  sense  the  term  carbohydrates  is  applied  to  all  alde- 
hyde alcohols  (aldoses)  and  ketone  alcohols  (ketoses)  of  the  polyhydric 
alcohols  which  contain  a  HO  group  attached  to  the  C  atoms  neighbor- 
ing the  aldehyde  or  ketone  groups,  as  well  as  their  anhydride-like  con- 
densation products. 

These  compounds  may  be  considered  in  connection  with  their 
corresponding  polyhydric  alcohols,  and  this  plan  has  been  adopted  in 
connection  with  the  carbohydrates  containing  less  than  six  atoms  of 
carbon.  According  to  the  number  of  C  atoms  the  carbohydrates  are 
now  also  called  biases  (C2H4O2,  p.  402),  trioses  (CjHeOj,  p.  433),  tetroses 


448  ORGANIC  CHEMISTRY. 

(C4H8O4,  p.  443),  pentoses  (C5H10O5,  p.  444) ,  hexoses  (CeHijOg), /leptoses 
(C7H14O7),  octoses  (CgHigOg),  nonoses  (CgHigOg). 

This  nomenclature  is  confusing  because  the  varieties  of  sugars  with  6 
C  atoms  are  often  called  monoses,  and  correspondingly  those  with  12  C 
atoms  bioses  and  those  with  18  C  atoms  trioses. 

Carbohydrates  in  the  narrow  sense,  or  saccharides  (from  saccharum, 
sugar),  are  those  carbohydrates  with  6  or  xQ  carbon  atoms  occurring 
in  nature.     These  are  divided  into  the  following  groups : 

Monosaccharides,  €^11^2^6. 
Disaccharides,       C,2H.,vOn. 
Trisaccharides,     C.gH^.Ce. 
Polysaccharides,    (CoH.oOa)^. 

All  aldoses  and  pentoses  with  5,  6,  etc.,  C  atoms  have  the  same 
structure  but  different  configuration  (p.  303)  and  are  therefore  stereo- 
isomers of  each  other.  The  stereoisomers  occur  dextro-  and  Isevorota- 
tory,  inactive  but  cleavable  (racemic,  p.  39),  and  inactive  but  not 
cleavable.  Correspondingly  the  presence  of  3-4  or  more  asymetric 
C  atoms  makes  the  number  of  possible  stereoisom.ers  very  large 
(p.  307).  Only  a  few  of  these  are  found  in  nature,  while  most  of  them 
have  been  prepared  synthetically. 

Occurrence.  Up  to  the  present  time  only  pentoses  and  saccharides 
have  been  found  in  nature.  They  are  especially  very  widely  dis- 
tributed in  the  plant  kingdom  and  certain  of  them  form  important 
constituents  of  all  plants.  Some  are  found  in  the  animal  kingdom, 
partly  under  normal  conditions  and  partly  under  pathological  con- 
ditions. 

Properties.  -The  mono-,  di-,  and  trisaccharides  have  a  sweet 
taste  and  are  crystallizable  while  the  polysaccharides  are  not  sweet, 
amorphous  or  are  organized  compounds.  Those  occurring  naturally  are 
soluble  in  water  and  are  optically  active  while  those  carbohydrates 
prepared  from  optically  inactive  compounds  are  also  optically  inactive 
but  can  be  decomposed  into  optically  active  modifications  (pp.  39  and 
306). 

The  carbohydrates  are  confusingly  designated  not  only  according  to 
the  rotation,  for  instance,  I-  or  d-  (p.  330),  but  also  all  carbohydrates 
obtained  from  I-  or  rf-compounds  even  when  they  have  another  rotation. 
Thus  the  laevorotatory  laevulose  obtained  from  c?-dextrose  is  designated 
cHaevulose,  etc.) 


CARBOHYDRATES.  449 

They  are  indifferent,  i.e.,  they  are  neither  acids  nor  bases.  On 
heating  they  decompose  into  bodies  of  simpler  constitution  and  leave 
carbon  as  a  residue.  On  oxidation  they  are  transformed  into  hexon 
acids  (p.  446) — respectively  saccharic  acid,  mannosaccharic  acid,  or 
mucic  acid  (p.  446) — and  on  stronger  oxidation  (fusion  with  caustic 
alkaUes,  etc.),  they  all  yield  oxalic  acid.  On  boiling  with  dilute  acids 
the  di-  tri-  and  polysaccharides  take  up  H^O  (see  Hydrolysis,  p.  87)  and 
are  converted  into  monosaccharides,  and  this  transformation  may  also 
be  brought  about  by  different  enzymes  (which  see).  With  nitric 
acid  they  form,  according  to  the  temperature,  etc.,  either  nitrates 
or  are  oxidized  to  simpler  compounds  (p.  322).  On  heating  with 
concentrated  mineral  acids  they  yield  levulinic  acid  and  humus 
substances. 

Certain  carbohydrates  .with  six  or  one  with  nine  C  atoms  readily 
suffer  a  deep  cleavage  by  means  of  organized  ferments  which  we  call 
fermentation  (p.  325).  The  chief  products  produced  in  this  cleavage 
are  alcohol,  lactic  acid  or  butyric  acid,  according  to  the  variety  of 
ferment.  Each  ferment  can  only  split  a  compound  of  a  certain 
configuration  (p.  303);  thus  yeast  can  only  ferment  dextrorotatory 
monosaccharides  and  Isevorotatory  laevolose,  while  the  disaccharides 
are  first  converted  into  the  fermentable  monosaccharides  by  the 
enzymes  of  the  yeast.  Many  carbohydrates  dissolve  metallic  oxides 
and  form  saccharates  corresponding  to  the  alcoholates  (p.  343).  The 
hydrogen  of  the  OH  groups  may  also  be  replaced  by  organic  acids, 
alcohol  radicals,  etc.  The  latter  compounds  are  widely  distributed 
in  thci  plants  and  are  called  glucosides  (which  see).  The  glucosides 
are  split  into  their  components  by  the  action  of  acids,  alkalies,  and 
ferments,  at  the  same  time  taking  up  water.  Similar  compounds  to 
C6H„06(CH3)  may  also  be  obtained  synthetically. 

Preparation.  Only  the  monosaccharides  and  those  carbohydrates 
closely  related  thereto,  but  not  found  in  nature,  containing  2-9  atoms 
of  carbon,  as  well  as  the  disaccharides  maltose  and  isomaltose,  have 
been  obtained  synthetically. 

The  discovery  of  E.  Fischer,  that  phenylhydrazin  forms  insoluble 
compounds  called  osazones  with  the  above-mentioned  carbohydrates, 
has  made  it  possible  to  precipitate  and  identify  the  artificially  obtained 
varieties  of  sugars  prepared  according  to  the  methods  to  be  described. 
The  separation  of  the    sugars  from  the   accompanying  by-products 


450  ORGANIC  CHEMISTRY. 

in  the  past  was  very  difficult,  as  the  impure  sugars  are  crystallizable 
with  difficulty. 

The  carbohydrates  in  question  unite,  on  account  of  their  containing 
aldehyde  or  ketone  groups,  with  1  molecule  of  phenylhydrazin ;  with  the 
elimination  of  HgO,  and  form  the  readily  soluble  nydrazones  (p.  351,  11). 

CeHj^O  6  +  H^N-NH  (CeHs)  =  CeH,  A=N-NH  (0,^,)  +  R,0. 

d-Glucose.       Phenlhydrazin.  d-Glucosohydrazone. 

The  hydrazones  or  the  carbohydrate  itself  when  in  acetic  acid  solution 
and  warmed  with  an  excess  of  phenylhydrazin  unites  with  a  second 
molecule  of  phenylhydrazin  and  yields  yellow,  insoluble,  crystalline  com- 
pounds called  osazones  or  dihydrazones;  thus,  rf-glucosohydrazone  yields 
d-glucosazone: 

CH2-OH-(CHOH),-CH=N-NH(C6H5)+H2N-NH(C6H5)  = 

H20  +  H2  +  CH20H-(CHOH)3-C(=N-NHC6HJ-CH=N-NH(C6H5). 

The  melting-point  of  the  osazones  serves  in  the  characterization  of  the 
different  sugars.  The  sugar  cannot  be  obtained  directly  from  the  osa- 
zones, but  only  indirectly;   thus: 

a.  The  osazones  are  decomposed  by  concentrated  HCl,  taking  up  2H2O, 
into  phenylhydrazin  and  osones: 

CeH.oO,  (=N-NH-C6H,),  +  2H,0= CeH.oOe  +  2H,N-NHCeHs. 

d-Glucosazcne.  d-Glucosone.     Phenylhydrazin. 

The  osones  contain  2  atoms  H  less  than  the  sugar  from  which  the  osazones 
are  obtained  and  yield  the  corresponding  ketose  by  reduction: 

CgHjoOo      +     Hg     =     CgHjaOe. 
d-GIucosone.  Laevulose  (laevorotatory). 

The  sugars  obtained  are  either  active  or  inactive.  These  latter  kinds  can 
be  decomposed  by  various  methods  into  the  two  oppositely  active  modi- 
fications of  which  they  are  constructed. 

The  preceding  example  shows  the  conversion  of  the  aldose  (glucose) 
into  the  ketose  (laevulose). 

6.  The  osazones  yield  glucosamines  on  direct  reduction  (the  glucos- 
amines or  amido  sugars  are  sugar  where  one  OH  group  is  replaced  by  an 
NHg  group) : 

CeH,oO,(=N-N-C6H,),  +  2H3  +  H,0= 

C6H,iO,(NH,)  +  H^N-Ce-H^  +  H,N-NH(C6H5). 

The  glucosamines   (see  Glycoproteids)  exchange,  on  treatment  with 

TOo,  the  NH2  group  for  the  OH  group  (p.  378 

sugar:   C6H„05(NH2)  +  HN02=C6H,206  +  N2  +  H20. 

1.  Mixtures  of  monosaccharides  called  methylenitan  can  be  obtained 
by  the  polymerization  of  paraldehyde  (p.  350)  and  formose  by  the  poly- 
merization of  formaldehyde  (p.  350).  On  the  condensation  of  glycerine 
aldehyde  with  dioxyacetone  (p.  433),  2C3HeO.^=CeH,20fi,  or  from  acro- 
leindibromide  and  baryta-water,  2C3H^Br20  +  2Ba(OH)2=C6Hi20e  + 
2BaBr„,  we  obtain  a-acrose. 


MONOSACCHARIDES.  451 

2.  Monosaccharides  and  the  related  carbohydrates  with  2  to  9  C  atoms 
can  be  obtained  by  the  careful  oxidation  of  the  respective  alcohols  and 
their  separation  as  osazones  or  glucosamines,  from  which  they  can  be  set 
free  in  the  manner  given  (p.  450)  and  finally  transformed  into  their 
optically  active  modification  (p.  39). 

3.  Monosaccharides  can  be  prepared  by  hydrolysis  of  the  di-,  tri-,  and 
polysaccharides  by  boiling  with  dilute  acids  or  by  ferments  (p.  324). 

4.  In  order  to  obtain  a  carbohydrate  rich  in  C  from  one  poorer  in  C 
we  proceed  as  follows:  The  carbohydrates,  on  account  of  their  containing 
the  aldehyde  and  ketone  groups,  unite  with  hydrocyanic  acid  (p.  351,  9), 
and  the  nitriles  produced  are  readily  transformed  into  acids  (p.  346,  2) : 

CH20H-(CH-0H),CH0  +  HCN  =  CH2-0H(CH0H),-CH0H-CNj 

Dextrose.  Dextroso-cyanhydrin. 

CH,-OH(CH-OH),-CHOH-CN  +  2H0H 

=  CH2OH-  (CH-  OH),-CH-  OH  •  COOH  +  NH3. 

Glucoheptonic  acid,  C7H14O8. 

The  acids  thus  obtained  yields,  on  splitting  off  HgO,  good  crystalline  lac- 
tones (p.  404,  a):  0H2C-(CH-0H),-CH-0H)C0;    and  these  by  reducing 

agents  yield  the  corresponding  aldose : 

H0-H2C(CH0H),-CH-0H-CH0. 

By  this  method  heptoses,  C7H14O7,  octoses,  CgHieOg,  and  nonoses,  CjHigOo, 
have  been  obtained;  thus,  from  arabinose,  C5H10O5,  we  obtain  arabinose 
cvanhydrin,  CgHioOgCHCN),  from  which  the  arabinose  carbonic  acid, 
CfeHigOy  or  C5H[ii05(COOH),  is  derived  and  from  this  by  internal  anhydride 
formation,  arabinose  carbonic  acid  lactone,  CgHjoOgCCO)  or  CjHioOj,  which 
on  reduction  yields  the  sugar  d-mannose,  Cfi^iJ^^. 

I.  Monosaccharides,  CjHiaOj. 
Glucose,  Laevulose,  Galactose,  Sorbinose,  Mannose. 

The  members  of  this  group  are  also  called  glucoses,  monoses,  hexoses; 
they  contain  5  HO  groups  and  occur  in  part  in  nature  and  some  of  them 
are  obtained  synthetically.  The  synthetically  prepared  carbohydrates 
containing  2-9  carbon  atoms  also  belong  to  this  group  on  account  of 
their  behavior.  They  all  contain  2  atoms  H  less  than  the  corre- 
sponding alcohols,  and  as  mentioned  on  p.  445,  they  can  be  converted 
into  alcohols  by  nascent  hydrogen  and  hence  they  are  the  aldehydes 
or  ketones  of  these  alcohols.  They  all  reduce  alkaline  solutions  of 
copper  and  silver,  and  like  all  aldehydes  and  ketones,  unite  with 
an  excess  of  phenylhydrazin,  forming  yellow,  crystalline  osazones 
(p.  450),  which  are  insoluble  in  water.  When  warmed  with  alkali 
hydroxides  they  turn  yellow,  then  brown,  and  finally  become  resinous. 

Dextrose,  grape-sugar,  rf-glucose,  glycose,  also  called  diabetic 
sugar,  starch-sugar. 


452  ORGANIC  CHEMISTRY. 

Occurrence.  In  many  sweet  fruits  and  in  honey  mixed  with 
Isevulose,  and  in  smaller  amounts  in  many  organs  of  the  animal  body, 
also  in  certain  pathological  urines  (to  10  per  cent.). 

Preparation.  By  the  action  of  dilute  acids  or  unorganized  fer- 
ments upon  cane-sugar  (accompanied  by  Isevulose),  also  upon  starch, 
cellulose,  and  many  glucosides.  It  is  prepared  on  a  commercial  scale 
by  boiling  starch  with  dilute  sulphuric  acid  under  pressure  and  recrjrs- 
talUzing  the  product. 

Properties.  Glucose  crystallizes  in  warty,  colorless  masses  with 
one  molecule  HjO.  From  its  solution  in  methyl  alcohol  it  crystallizes 
in  fine,  anhydrous  prisms  which  melt  at  146°.  It  is  about  half  as 
sweet  as  cane-sugar  and  dissolves  in  cold  sulphuric  acid  without 
blackening,  also  in  an  equal  weight  of  water.  The  fresh  solution 
has  twice  the  dextrorotatory  power  of  an  older  solution  (so- 
called  multi-  or  birotation).  It  reduces  metalHc  silver,  as  a  mirror, 
from  an  ammoniacal  silver  solution  and  red  cuprous  oxide,  from  an 
alkaline  cupric  salt  solution  (Fehling's  solution,  p.  236),  slowly  in  the 
cold  and  immediately  on  heating. 

d-Glucose  is  converted  into  d-sorbite  by  nascent  hydrogen  and  on 
oxidation  it  yields  acids  having  the  same  amount  of  carbon,  gluconic  acid, 
CgHiaOj,  and  saccharic  acid,  CjHjoOg.  Glucose  therefore  contains  an  alde- 
hyde group  and  is  an  aldose  having  the  structure  CH20H(CH-0H)^-CH0. 

Laevulose,  fructose,  diabetin,  c?-laevulose  (so-called  on  account  of  its 
preparation  from  c?-glucosazone,  although  it  is  Isevorotatory  (p.  448). 

Occurrence.  It  is  found  with  grape-sugar  in  most  sweet  fruits 
and  in  honey. 

Preparation.  Accompanied  with  d-dextrose  from  cane-sugar  by 
the  action  of  unorganized  ferments  or  by  boiling  with  dilute  inorganic 
acids.  From  inulin  by  boiling  with  dilute  mineral  acids  or  mixed 
with  d-mannose  from  c?-mannite  by  oxidation. 

Properties.  It  differs  from  dextrose  only  by  its  melting-point 
(95°),  in  the  property  it  has  of  Isevorotation  (hence  the  name 
Isevulose)  and  by  being  less  crystallizable;  but  it  occurs  ordinarily 
as  a  colorless  sweet  sirup  which  is  not  very  soluble  in  water  but 
readily  soluble  in  alcohol. 

With  nascent  hydrogen,  Isevulose  yields  <i-mannite,  as  it  is  first  con- 
verted into  d-mannose;  on  oxidation  it  yields  glycoUic  and  racemic 
acids,  products  having  less  C;  hence  it  is  a  ketose  of  the  structure 
CH20H(CHOH),-CO-CH20H. 

d-Galactose,  cerebrose,  a  stereoisomer  of  d-glucose,  occurs  in  the  brain 


DISACCHARIDES.  453 

and  is  produced,  accompanied  with  c?-glucose,  from  milk-sugar  as  well  as 
from  dextrorotatory  varieties  of  gums  on  warming  with  dilute  acids.  It 
is  more  dextrorotatory  than  d-glucose  and  is  insoluble  in  alcohol.  With 
nascent  hydrogen  it  yields  inactive  dulcite,  and  on  oxidation  galactonic 
acid,  CgHijO;,  and  then  mucic  acid,  CgHioOg,  are  produced. 

^-Sorbinose,  sorbin,  sorbose,  is  a  ketose  stereoisomeric  with  Isevulose, 
and  occurs  in  the  juice  of  the  mountain-ash  when  it  has  stood  for  a  long  time. 
It  forms  colorless  crystals  whose  solutions  reduce  alkaline  copper  solu- 
tions, but  is  not  fermentable  with  yeast.  It  is  not  changed  on  boiling 
with  acids  and  yields  trioxyglutaric  acid,  CgHgOy  (p.  425),  and  with 
nascent  hydrogen  it  is  converted  into  c?-sorbite,  CgHi^Oe  (p.  446). 

d-Mannose,  seminose,  a  stereoisomer  of  d-glucose,  is  obtained  with 
rf-laevulose  on  the  careful  oxidation  of  mannite  as  well  as  by  boiling  the 
carbohydrate  seminin,  occurring  in  the  earth-nut,  with  dilute  acids.  It 
yields  mannonic  acid,  CgHiaO;  (p.  446),  on  oxidation  and  mannite  (p.  445) 
on  reduction  with  nascent  hydrogen. 

2.  Disaccharides,  C^JI^O,^. 
Saccharose,  Lactose,  Maltose,  Mycose,  Melebiose,  Isomaltose. 
The  bodies  of  this  group  are  also  called  saccharoses  or  bioses 
(p.  448)  and  contain  8  hydroxyl  groups.  They  are  anhydrides  of 
two  generally  different  monosaccharides  (hence  the  name  disaccha- 
rides)  and  decompose  on  heating  with  dilute  acids  into  monosaccha- 
rides, at  the  same  time  taking  up  one  molecule  HjO  (by  hydrolysis) : 

C,3H,,0„+H30  =  CeH,,0„+CeH,,Oe. 

Saccharose,  cane-sugar,  beet-root  sugar,  is  the  anhydride  of  d-g\\i- 
cose  and  Wsevulose.  Occurrence.  In  the  juice  of  many  plants,  espe- 
cially in  the  sugar-cane  (to  18  per  cent.)  and  the  sugar-beet  (to  20 
per  cent.),  from  which  it  is  chiefly  obtained  by  evaporation.  It  is 
principally  found  in  the  stem  or  the  roots  of  the  plants,  while  glucose 
and  Isevulose  occur  to  the  greatest  extent  in  the  fruits. 

Preparation.  The  juice  from  the  sugar-cane  or  the  sugar-beet  is  heated 
to  boiling  with  milk  of  lime  (calcium  hydroxide),  whereby  the  plant  acids 
are  neutralized  (p.  454)  and  the  proteids  are  coagulated  and  separate  as  a 
scum.  At  the  same  time  a  part  of  the  calcium  oxide  forms  with  the  sugar 
a  soluble  calcium  saccharate,  CiaHggOu+CaO.  The  juice  is  now  treated 
with  carbon  dioxide,  when  a  large  part  of  the  lime  is  precipitated  as 
calcium  carbonate  and  at  the  same  time  a  considerable  amount  of  con- 
tamination is  precipitated  out.  After  the  separation  of  the  precipitate 
the  hot  juice  is  filtered  through  bone-black,  which  removes  the  coloring 
matters  and  some  contained  lime  and  a  part  of  the  salts.  The  filtrate  is 
evaporated  to  a  sirupy  consistency  in  vacuum-pans,  when  on  cooling  the 
cane-sugar  crystallizes  out.  The  sirupy,  brown  mother-liquor,  molasses, 
contains  still  about  50  per  cent,  of  sugar,  which  is  prevented  from  crys- 
tallizing by  the  contained  salts_]and  organic  substances  (about  30  per  cent.). 


454  ORGANIC  CHEMISTRY. 

Cane-sugar  molasses  has  a  pure  sweet  taste  and  is  often  used  instead 
of  sugar,  as  well  as  in  the  preparation  of  rum  (p.  355). 

Beet-root  molasses  is  used  for  feeding  cattle,  or  alcohol  is  prepared  there- 
from by  fermentation,  or  the  sugar  it  contams  is  abstracted  by  the  follow- 
ing method:  It  is  boiled  with  an  excess  of  strontmm  hydrate,  which  pre- 
cipitates the  sugar  as  strontium  saccharate,  CigHggO,,  +SrO,  which  quickly 
settles  and  which  can  be  transformed  into  crystallizable  sugar  and  stron- 
tium carbonate  by  means  of  carbon  dioxide.  Another  method  is  to 
remove  the  salts,  preventing  the  crystallization  of  the  sugar  by  means  of 
dialysis  (so-called  diffusion  method).  The  residue  left  after  fermentation 
or  after  the  abstraction  of  the  sugar  is  incinerated  in  order  to  obtain  the 
potash  (p.  207). 

Properties.  White  crystalline  masses  or  white  crystalline  powder. 
Cane-sugar  crystallizes,  on  slow  evaporation,  in  large  monoclinic 
prisms  (rock-candy),  has  a  sweeter  and  purer  taste  than  grape-sugar, 
and  is  not  very  soluble  in  alcohol  but  readily  soluble  in  water, 
forming  a  colorless,  sweet,  dextrorotatory  sirup.  On  heating  to 
160°  it  melts  and  solidifies  on  cooling,  forming  an  amorphous  vitreous 
mass  (barley-sugar)  which  after  a  certain  time  becomes  crystalline  and 
then  opaque.  On  heating  to  190-200°  it  is  converted  into  caramel, 
C12H18O9,  an  amorphous,  not  sweet,  unfermentable,  brown  mass  which 
is  readily  soluble  in  alcohol  and  used  as  sugar  color  in  the  coloring 
of  liquors,  etc.  On  further  heating  it  decomposes  with  the  genera- 
tion of  inflammable  vapors  and  leaves  porous  shining  carbon.  On 
boiling  with  dilute  acids  (even  with  organic  acids,  hence  the  neutral- 
ization of  these  in  the  preparation  of  sugar,  p.  453)  it  decomposes 
into  a  mixture  of  dextrose  and  laevulose,  so-called  invert-sugar,  which 
is  Isevorotatory,  because  the  Isevulose  turns  the  plane  of  polarized 
Hght  stronger  to  the  left  than  an  equal  amount  of  dextrose  does  to 
the  right: 

Ci2H220u+  H2O  =  C6H12O6+  C6H12O6. 

When  heated  with  alkalies  cane-sugar  does  not  turn  brown,  differing 
from  glucose  and  milk-sugar. 

Concentrated  sulphuric  acid  carbonizes  it  even  in  the  cold  with  the 
generation  of  SO,.  On  warming  with  HNO.,  saccharic  acid  is  produced: 
C12H22O1  +60=2C6Hi„Og+H20;  and  on  boiling  with  HNO3  oxalic  acid 
is  obtaiiied:   C.^U^^O,,  + 180=  GC^HA  +  SHgO. 

Alkaline  solutions  of  silver  or  copper  are  only  reduced  after  inversion 
(after  boiling  for  a  long  time).  Cane-sugar  is  not  directly  fermentable, 
but  if  yeast  is  added  to  a  solution  of  cane-sugar  it  is  transformed  into 
fermentable  invert^sugar  by  the  invertase  existing  in  the  yeast.  The 
aqueous  solution  of  cane-sugar  dissolves  many  metallic  oxides  to  a  great 
extent  (see  preparation),  these  solutions  having  a  bitter  taste  and  strong 
alkaline  react'on. 


DISACCHARIDES.  455 

Lactose,  milk-sugar,  lactobiose,  is  the  anhydride  of  c?-glucose 
and  c?-galactose. 

Occurrence.  In  milk,  amniotic  fluid,  in  certain  pathological 
secretions,  in  the  urine  of  sucking  animals. 

Preparation.  Milk  which  has  been  freed  from  casein  and  fat 
(the  whey)  is  evaporated  to  crystallization  and  the  milk-sugar  thus 
obtained  purified  by  recrystallization. 

Properties.  It  forms  crystalline  masses  with  1  mol.  HgO,  or  a 
crystalline  powder  which  dissolves  in  7  parts  cold  water  and  1 
part  boiling  water,  producing  a  faintly  sweet,  dextrorotatory,  not 
sirupy  solution  which  shows  birotation  (p.  452).  Lactose  is  nearly 
insoluble  in  dilute  alcohol  (used  in  detecting  admixture  with  cane- 
sugar). 

On  boiling  with  dilute  acids  lactose  is  converted  into  a  mixture  of 
rf-galactose  and  d-glucose;  by  nascent  hydrogen  it  is  transformed  into 
mannite  and  dulcite.  It  does  not  ferment  with  pure  yeast,  although  it 
readily  undergoes  lactic-acid  fermentation  by  the  action  of  certain  fungi, 
especially  in  milk.  It  undergoes  alcoholic  fermentation  by  the  kephir 
and  tyrocola  fungus  (p.  325).  On  warming  with  nitric  acid  it  is  oxidized 
to  mucic  acid,  and  on  boiling  with  HNO3  oxaUc  acid  is  obtained.  It  is 
not  decomposed  by  cold  concentrated  sulphuric  acid.  It  reduces  an 
ammoniacal  silver  solution  even  in  the  cold,  but  an  alkaline  copper  solu- 
tion is  only  reduced  on  heating  (differing  from  glucose).  On  boiling  for 
a  long  time  with  dilute  H2SO4  levulinic  acid  is  produced  (p.  371).  On 
heating  to  180°  it  is  converted  into  lactocaramel  (p.  454). 

Maltose,  malt-sugar,  maltobiose,  is  the  anhydride  of  c?-glucose.  It  is 
found  in  the  contents  of  the  small  intestine,  and  is  the  sugar  formed  besides 
dextrins  by  the  action  of  the  enzyme  diastase  (malt)  upon  starch: 

SCeH.oO^  +  HP^  C,3H,,.0,,  +  CeH,„p,. 
Maltose.        Dextrin. 

It  can  be  synthetically  prepared  from  c?-glucose.  It  crystallizes  with  1 
mol.  HgO  as  hard  white  masses  which  consist  of  needles.  It  has  a 
greater  dextrorotatory  action  and  is  less  soluble  in  alcohol  than  dextrose, 
and  is  split  into  2  mol.  d-glucose  by  boiling  with  dilute  HgSO^,  as  well 
as  by  the  action  of  the  enzyme  maltase.  Maltose  reduces  alkaline  cop- 
ner  solutions  even  in  the  cold,  but  to  a  less  degree  than  dextrose.  It 
readily  ferments  with  yeast,  as  the  enzyme  maltase  of  the  yeast  first  splits 
it  into  fermentable  d-glucose. 

Melibiose,  the  anhydride  of  <f-glucose  and  c?-galactose,  is  obtained, 
besides  d-lsevulose,  in  the  inversion  of  melitriose  and  is  stereoisomeric 
with  milk-sugar. 

Isomaltose  is  prepared  synthetically  from  c?-glucose,  and  is  produced 
with  maltose  by  the  action  of  diastase  upon  starch.  It  has  a  weaker 
reducing  power  than  maltose,  but  is  not  fermentable. 

Mycose,  trehalose,  is  found  in  certain  fungi,  in  ergot,  in  the  Manna 
trehala. 


456  ORGANIC  CHEMISTRY. 

3,  Trisaccharides,  CisHgPu. 
Melitriose,  Gentianose,  Stachyose,  Melezitose. 

The  members  of  this  group  are  to  be  considered  as  formed  by  the  union 
of  equal  molecules  of  the  sugars,  CqH^^Po  and  CigHagO,!,  with  the  elimina- 
tion of  one  melocule  of  water.  On  boiling  with  dilute  acids  they  take  up 
water  and  decompose  into  different  molecules. 

Melitriose,  gossypose,  melitose,  raffinose,  the  anhydride  of  melibiose 
and  d-lsevulose,  CigHggOij  +  SHgO,  occurs  in  the  Eucalyptus  manna,  in  the 
sugar-beet  to  a  slight  extent,  and  in  the  cottonseed.  As  it  is  more  solu- 
ble than  cane-sugar,  it  is  found  in  cane-sugar  molasses.  The  presence  of 
melitriose  in  cane-sugar  causes  it  to  have  a  greater  rotation,  because  meli- 
triose has  a  greater  dextrorotatory  power  than  cane-sugar.  It  does  not 
reduce  copper  solutions,  but  does  ferment  with  yeast. 

Gentianose,  C10H32O18,  occurs  in  the  roots  of  the  Gentiana  lutea. 

Stachyose,  C,gH320iB-f3H20,  in  the  Stachys  tubifera. 

Melezitose,  CigHgaOu  +  SHgO,  is  found  in  the  juice  of  the  larch-tree. 

4.  Polysaccharides,  (CqEiJO^). 

Cellulose,  Starch,  Lignin,  Inulin,  Dextrin,  Glycogen,  Lichenin,  Gums, 
Plant-mucilages,  Pectine  Bodies. 

The  members  of  this  group  may  be  considered  as  complicated  anhy- 
drides of  one  glucose,  as  they  yield  only  one  variety  of  sugar  on  heating 
with  dilute  acids.  Their  molecular  weight  is  at  all  events  (CeHioOs)^;, 
hence  they  are  called  polysaccharides.  They  differ  from  the  other 
two  groups  by  not  being  crystalline,  but  are  either  amorphous  or 
organized  and  then  insoluble  in  water. 

Cellulose,  Lignose.  Occurrence.  Forms  with  lignin  (p.  458)  and 
the  pentosanes  (p.  444)  the  crude  fibre,  the  chief  constituent  of  the 
cell- walls  of  all  plants,  and  has  an  organized  structure  (p.  4).  Puri- 
fied cotton  and  filter-paper  are  nearly  pure  cellulose.  Paper  is  more 
or  less  pure  cellulose  which  has  been  freed  from  lignin,  etc.,  by  heating 
with  concentrated  caustic  alkali  or  alkali  sulphide  solution  or  calcium 
bisulphite  solution  under  pressure.  The  calcium  bisulphite  solution 
obtained  is  called  lignosulphite  and  is  used  in  medicine. 

Preparation.  Plant-fibres  (cotton  wool  or  filter-paper)  is  treated 
consecutively  with  dilute  caustic  alkali,  dilute  sulphuric  acid,  water, 
alcohol,  and  ether,  which  removes  all  impurities  and  leaves  pure 
cellulose. 

Properties.  White  amorphous  powder,  only  soluble  without 
change  in  an  ammoniacal  solution  of  copper  oxide  (p.  236).  It  is 
precipitated   from   this   Isevorotatory   solution   by   acids.      Concen- 


POLYSACCHARIDES,  457 

trated  sulphuric  acid  transforms  cellulose  after  short  action,  without 
dissolving  it,  into  a  substance  which  is  colored  blue  by  iodine  (detec- 
tion of  cellulose).  After  a  longer  action  it  dissolves  in  concentrated 
H2SO4  without  blackening,  and  from  this  solution  colloidal  cellulose 
may  be  precipitated  by  water;  this  precipitate  turns  blue  with  iodine 
and  shows  by  this  reaction,  as  well  as  by  the  formation  of  closely 
related  bodies,  many  similarities  with  starch  and  hence  has  been  called 
amyloid  (not  to  be  confounded  with  the  amyloid  substance,  a  proteid). 
If  sulphuric  acid  is  allowed  to  act  a  still  longer  time,  dextrin  is  pro- 
duced, and  if  this  is  diluted  with  water  and  boiled,  the  dextrin  is 
transformed  into  dextrose. 

If  unglazed  paper  is  dipped  for  a  short  while  into  dilute  sulphuric 
acid  and  then  washed  with  water,  the  surface  of  the  paper  is  trans- 
formed into  amyloid  and  forms  parchment-paper  which  is  used  ex- 
tensively because  of  its  similarity  to  parchment.  On  boiling  with 
nitric  acid  or  on  fusing  with  caustic  alkalies,  cellulose  is  oxidized 
into  oxalic  acid.  On  putrefaction  CO2  and  CH4  are  produced,  these 
products  occurring  in  the  intestine  from  the  cellulose  of  the  food 
(p.  346).  Animal  cellulose  in  the  covering  of  the  tunicates  is  very 
similar  to  cellulose. 

Hydrocelluloses  are  the  compounds  produced  by  the  action  of  sul- 

f)huric  acid  or  hydrochloric  acid  of  certain  concentration  upon  the  cellu- 
oses  (hydration  products),  and  occur  in  plants  as  so-called  hemicelluloses. 
Oxycelluloses  are  oxidation  products  of  the  celluloses  which  contain 
the  carboxyl,  aldehyde,  and  ketone  groups  and  which  also  occur  in  the 
plants. 

Cellulose  nitrates,  incorrectly  called  nitro-celluloses,  are  formed 
when  cold  nitric  acid  acts  upon  cellulose,  such  as  cotton.  The  prop- 
erties of  these  esters  depend  upon  the  length  of  action  and  the 
strength  of  the  nitric  acid  used.  In  appearance  they  do  not  differ 
from  the  cotton  or  cellulose. 

With  caustic  alkali  or  calcium  sulphide  or  ferrous  chloride  solution  they 
yield  cellulose: 

C6H803(N03)2  +  6FeCl2  +  6HC1=  C8H803(OH)2  +  GFeClg  +  2N0  +  2H2O. 

Guncotton,  pyroxylin,  cellulose  trinitrate,  C6H7N02(N03)3,  is  formed  by 
the  action  of  concentrated  nitric  acid  (HNO3  +  H2SO4)  and  burns  without 
explosion,  but  explodes  violently  when  confined  in  an  enclosed  space  by 
shock  or  by  ignition  with  mercury  fulminate.  It  is  insoluble  in  a  mixture 
of  alcohol  and  ether. 

Smokeless  powder  consists  of  guncotton  which  has  been  converted  mto 
an  amorphous  transparent  mass  by  moistening  with  acetone,  and  explodes 
more  slowly  when  granular  than  the  original  guncotton. 


458  ORGANIC  CHEMISTRY. 

One  gram  guncotton  yields  860  c.c.  explosion-gases  (p.  207),  which 
expand  to  7800  c.c.  the  moment  they  are  set  free  by  the  heat  generated. 

Collodium  cotton,  colloxylin,  cellulose  nitrate,  C6H904(N03),  and  cellulose 
diniirate,  C6H803(N03)2,  are  formed  by  the  action  of  less  concentrated 
nitric  acid,  are  not  explosive,  and  are  soluble  in  alcohol-ether  mixture, 
forming  collodium. 

Collodium  leaves  the  colloxylin,  on  evaporation,  as  a  transparent  film 
(celloidin).  Collodium  cantharidatum  contains  the  ethereal  extract  of 
the  Spanish-fly.  Collodium  elasticum  contains  some  castor-oil  and  tur- 
pentine. Zapon  varnish  is  a  solution  of  collodium  cotton  in  acetone  or 
amyl  acetate.  Celluloid,  the  substitute  for  hard  rubber,  is  collodium 
cotton  impregnated  with  camphor  which  is  pressed  and  rolled. 

Dualin,  lithofracteur,  Brain's  powder,  is  a  mixture  of  glycerine  trini- 
trate with  sawdust,  etc.,  which  has  previously  been  treated  with  nitric 
acid  or  sulphuric  acid.  Explosive  gelatine  is  guncotton  impregnated 
with  glycerine  trinitrate.  Artificial  silk,  which  is  very  similar  to  natural 
silk,  is  prepared  by  pressing  collodion  into  water  and  treating  the  very 
fine  fibres  of  collodion  wool  thus  obtained  with  calcium  sulphide,  which 
reduces  them  to  silky  cellulose  fibres. 

Lignin,  xylogen,  incrusting  substance,  occurs  with  cellulose  as  the 
chief  constituent  of  wood,  and  is  similar  to  it.  It  dissolves  readily  in 
HNO3  +  KCIO3,  which  serves  in  separating  it  from  cellulose.  Bodies  con- 
taining lignin  turn  yellow  in  the  air  and  light  and  also  with  aniline  sul- 
Ehate,  and  beautifully  red  with  a  solution  of  phloroglucin  in  concentrated 
LCI  (detection  of  lignin  in  paper). 

Starches,  Amylum.  Occurrence.  They  are  found  in  nearly  all  plants, 
although  not  always,  as  microscopic  granules  of  an  organized  structure 
whose  size  and  configuration  differ  in  the  various  species  of  plants, 
and  this  fact  is  used  to  differentiate  between  the  various  starches. 

The  starch  granule  consists  chiefly  of  starch,  which  is  called  starch 
granulose  and  starch  cellulose,  also  called  farinose,  which  forms  the 
structure  of  the  grains  and  remains  unchanged  by  the  action  of  water, 
etc. 

Preparation.  On  a  large  scale  it  is  chiefly  prepared  from  potatoes, 
wheat,  or  rice,  which  are  macerated  with  water  to  a  paste  and  then 
kneaded  on  sieves  with  water.  The  starch  is  hereby  washed  out  and 
passes  through  the  meshes  of  the  sieve,  while  the  cell  membrane,  the 
gluten,  etc.,  remain  behind.  The  starch  is  now  allowed  to  settle 
and  dried. 

Properties.  White  odorless  powder  which  is  soluble  in  an  aqueous 
solution  of  chloral  hydrate  but  insoluble  in  cold  water,  alcohol,  and 
ether.  It  attracts  water  from  the  air,  and  when  treated  with  boiling 
water  it  is  converted  into  a  slimy  mass  which  forms  a  paste  on  cooling 
and  a  hard  mass  on  drying.  If  this  paste  is  boiled  for  a  long  time 
with  considerable  water,  the  starch  dissolves  and  alcohol  precipitates 


POLYSACCHARIDES,  459 

from  this  solution  a  white  amorphous  powder  which  is  soluble  in 
water  {soluble  starch,  amidulin).  The  solution  is  dextrorotatory, 
and  on  heating  to  160-200°  the  starch  is  transformed  into  dextrin 
(starch  gum).  On  boiling  with  dilute  acids  starch  is  converted  into 
dextrin  and  finally  into  dextrose,  at  the  same  time  taking  up  water. 
By  the  action  of  malt  diastase  it  is  first  converted  into  soluble  starch 
and  then  into  dextrin,  and  finally  into  maltose  and  isomaltose. 

Concentrated  sulphuric  acid  dissolves  starch  with  the  formation 
of  starch-sulphuric  acid,  which  forms  salts  with  bases.  Concentrated 
nitric  acid  dissolves  starch,  and  on  diluting  with  water  xyloidin, 
Ci2Hi909(N03),  precipitates  out;  this  xyloidin  is  explosive  like  the 
cellulose  nitrates.  On  heating  with  nitric  acid  oxahc  acid  is  produced. 
The  deep  blue  coloration  obtained  by  an  aqueous  solution  of  iodine 
(p.  143)  with  starch  is  characteristic  of  dissolved  starch,  as  well  as  the 
starch  in  the  grains.  This  coloration  disappears  on  heating  and  reap- 
pears on  cooling,  and  is  used  in  the  detection  of  starch. 

The  most  important  forms  of  starch  are  wheat  starch,  potato  starch, 
arrowroot  starch,  sago  and  tapioca  or  cassava  starch. 

Inulin,  found  in  the  roots  of  Inula  helenium,  is  soluble  in  hot  water 
and  turns  yellow  with  iodine. 

Glycogen,  liver-starch,  animal  starch,  occurs  in  the  liver,  in  all  devel- 
oping animal  cells,  in  many  fungi,  and  in  certain  higher  plants.  It  exists 
to  a  greater  extent  in  horse-muscles,  in  the  foetus,  and  in  mollusks.  On 
the  death  of  the  animal  it  is  quickly  transformed  into  dextrose.  It  is  an 
amorphous  colorless  powder  which  turns  reddish  brown  with  iodine  and 
is  soluble  in  hot  water,  giving  a  dextrorotatory  power  to  the  solution. 

Lichenin,  moss  starch,  occurs  in  Iceland  moss,  is  soluble  in  hot  water, 
and  turns  blue  with  iodine. 

Dextrins,  Starch  Gum.  Occurrence  and  Formation.  Dextrins 
is  the  name  given  to  a  series  of  intermediary  products  produced 
in  the  transformation  of  the  starches  into  sugar,  and  of  these  only 
amylo-,  erythro-,  malto-,  and  three  achroodextrins  have  been  closely 
studied  up  to  the  present  time.  Dextrins  are  formed  by  gently  roast- 
ing starch,  as  well  as  by  the  short  action  of  malt  diastase  or  saliva 
upon  starch  (occurrence  in  the  crust  of  bread  and  in  beer).  It  is  pre- 
pared on  a  large  cale  (as  a  substitute  for  gum  as  an  adhesive  body) 
by  moistening  starch  with  2  per  cent,  nitric  acid  and  drying  in  the 
air  and  then  heating  to  110°. 

Properties.  Yellow  amorphous  masses  readily  soluble  in  water 
and  dextrorotatory,  but  insoluble  in  alcohol.  Most  dextrins  do 
not  reduce  alkaline  copper  solutions  even  on  boiling,  and  are  only 


460  ORGANIC  CHEMISTRY. 

fermentable  by  certain  kinds  of  yeast.  They  are  readily  transformed 
into  dextrose  by  dilute  acids  and  converted  into  maltose  by  diastase. 
On  oxidation  they  yield  oxalic  acid.  Amylodextrin  turns  violet 
with  iodine,  erythrodextrin  red,  while  the  others  do  not  change  in 
color. 

Gums,  arabin,  arable  acid  is  the  chief  constituent  of  the  gums  occur- 
ring in  many  plants,  and  is  amorphous  and  readily  soluble  in  water,  but 
insoluble  in  alcohol.  The  aqueous  solutions  do  not  reduce  alkaline 
copper  solutions,  but  are  precipitated  by  basic  lead  acetate.  By  dilute 
acids  the  Isevorotatory  gums  are  converted  into  arabinose,  while  the  dextro- 
rotatory ones  yield  galactose  (p.  453).  Nitric  acid  oxidizes  it  into  mucic 
acid  or  oxalic  acid,  while  iodine  does  not  produce  any  color.  Gum  arabic 
consists  of  the  calcium  and  potassium  compounds  of  arabin.  Gum  mucilage 
is  a  sirupy  solution  of  gum  arabic  in  water. 

Animal  gum,  occurring  in  the  mucin  of  different  organs,  in  chondrin, 
in  the  brain-tissue,  etc.,  is  similar  to  the  plant-gums. 

Plant-mucilage,  Bassorin,  shows  the  general  properties  of  the  gums, 
from  which  it  differs  by  forming  a  mucilaginous  solution  with  water  which 
cannot  be  filtered.  It  readily  dissolves  in  alkalies.  It  forms  the  chief 
constituent  of  gum  tragacanth,  of  Bassora  gum,  of  cherr}"^  and  plum  gum. 
Certain  seeds,  tubers,  and  roots,  such  as  linseed,  quince-kernels,  salep,  etc., 
are  rich  in  vegetable  mucilages. 

Pectine  Bodies.  In  certain  fruits,  roots,  and  barks  we  find  non-nitro- 
genous amorphous  bodies  which  are  precipitated  from  their  aqueous  solution 
by  alcohol  as  gelatinous  precipitates  and  called  pectine  bodies,  vegetable 
gelatine,  or  pectine.  On  account  of  the  presence  of  these  bodies  many 
fruits  solidify  to  a  jelly  after  boiling  (fruit  jellies).  The  pectine  bodies 
are  closely  related  to  the  vegetable  mucilages,  but  have  less  characteristic 
properties  and  are  readily  changed.  They  are  derived  from  a  body, 
pectose,  which  is  insoluble  in  water  and  which  forms  with  cellulose  the 
chief  mass  of  many  fruits.  Pectose  is  transformed  by  dilute  acids  or 
alkalies,  or  by  an  enzyme  pectase  which  occurs  in  the  ripe  fruit,  into  pectic 
acids,  which  by  hydrolysis  are  split  into  acids  and  pentoses  or  hexoses  and 
which  are  related  to  the  oxycelluloses. 


n.  ISOCARBOCYCLIC  COMPOUNDS. 

CONSTITUTION. 

Isocarbocyclic  compounds  (p.  326)  are  those  compounds  whose 
molecule  contains  a  ring-formed  group  of  C  atoms  and  are  all  derived 
from  benzene,  CgHe,  whereby  its  H  atoms  are  partly  or  entirely  replaced 
by  monovalent  atoms  (p.  465)  or  by  groups  of  atoms  (side  chains), 
thus: 

CeHsCl  CeH3(OH)3  CeH.CCHj),  CeCl« 

Monochlorbenzene.  Pyrogallol.  Durene.  Hexochl  jrbenzene. 

All  isocarbocyclic  compounds  therefore  contain  a  group  of  six  C 
atoms  united  together,  18  of  the  24  valences  having  been  satisfied, 
while  6  valences  are  free  to  unite  with  other  atoms,  etc.  Although 
in  these  compounds  each  of  the  6  C  atoms  only  has  one  free  valence, 
still  they  behave  somewhat  like  saturated  compounds  and  cannot  be 
converted  into  these  without  destruction  of  the  molecule.  For  exam- 
ple, the  saturated  hydrocarbon  corresponding  to  benzene,  CgHp,  must 
have  the  formula  CeHj^  (p.  297),  while  benzene  only  slowly  takes  up  H 
atoms,  etc.,  by  addition  and  forms  bodies  up  to  C6H12,  so  that  of  the 
24  valences  of  its  6  C  atoms,  12  are  always  mutually  satisfied  in  the 
molecule,  but  still  in  a  different  way  from  the  isomeric  unsaturated 
aliphatic  compounds,  the  olefines  (p.  394). 

This  peculiar  behavior  of  this  carbon  group  of  existing  with 
only  6  free  valences,  as  well  as  the  chemical  behavior  of  all  the  com- 
pounds belonging  thereto  (see  Substitution) ,  and  above  all  the  isomeric 
possibilities  of  these  compounds  (see  Isomerism,  p.  466) ,  can  be  best 
explained  by  admitting  that  the  6  C  atoms  are  alternately  united  to 
each  other  by  one  or  two  bonds,  and  that  the  last  C  atom  is  united 
with  the  first,  so  that  the  6  C  atoms  form  a  closed  ring-like  chain,  a 
so-called  benzene  ring  (K^kul^'s  benzol  theory),  thus: 

461 


462 


ORGANIC  CHEMISTRY, 


He 


— c 


or    — C 


0— 


0— 


/ 


/ 


The  constitution  of  the  benzene  ring  is  not  the  same  in  all  benzene 
derivatives,  but  dependent  upon  the  nature  and  position  of  the  atoms  or 
atomic  groups  introduced,  so  that  recently  different  benzene  formulae  have 
been  suggested.  Of  these  Clauss's  diagonal  and  Baeyer's  central  formula 
correspond  best  with  the  facts;  still  these  formula}  require  some  modifica- 
tion if  we  accept  the  theory  of  the  tetrahedral  C  atoms  in  space. 


A 


V 


5  3 

4 


H 


H 


Hs?    4     ^^H 


H 


Central  Formula.        Diagonal  Formula.     Hexagon  Scheme.     Benzene,  CeHo. 

In  writing  the  structural  formulae  of  benzene  derivatives  we  often  do 
not  express  the  mutual  bonds  between  the  C  atoms,  and  only  use  a  simple 
hexagon  in  which  each  angle  represents  a  carbon  atom  with  its  one  free 
valence. 

In  benzol  one  H  atom  is  united  to  each  of  the  six  carbon  atoms. 
These  six  H  atoms  may  be  replaced  by  atoms  or  atomic  groups  (sub- 
stitution, p.  464),  thereby  producing  benzene  derivatives.  Neverthe- 
less in  all  these  compounds  the  carbon  ring  can  only  be  ruptured 
with  the  greatest  difficulty  by  chemical  action,  i.e.,  the  cyclic  com- 
pounds are  very  stable  and  can  only  in  a  few  instances  be  trans- 
formed into  alipathic  compounds  containing  the  same  number  of 
C  atoms.  The  benzenes  are  only  completely  destroyed  by  very  ener- 
getic oxidation  with  the  formation  of  carbon  dioxide,  formic  and 
acetic  acids. 


CONSTITUTION.  4i63 

Besides  the  isocarbocyclic  compounds  with  one  C  ring  in  the 
molecule  we  have  those  with  several  C  rings  chained  and  condensed 
together  (p.  298). 

Monovalent  atoms,  etc.,  may  also,  as  mentioned  on  p.  461,  unite 
directly  with  benzene  and  its  derivatives,  although  not  more  than  six 
are  possible.  The  benzene  ring  remains  closed  in  these  compounds, 
and  the  double  bonds  of  the  C  atoms  are  all  of  them  or  in  part 
changed  into  single  bonds: 

Benzene,  CfiH  6.    Dihydrobenzene,  CgHg.    Hexahydrobenzene,  CgHij. 

H  H  H, 

^  i  .    1! 

^\  ^\  /\ 

H-C        C-H  H-C        C-H  H2=C        C=H. 

I         II  I  il  II 

H-C        C-H  R-C        C-H  H2=C        C^Jl^ 

x/  \/  \/ 

C  c  c 

H  Hj  Hj 

The  benzene  ring  in  CgHe  is  also  called  tertiary,  in  CgHij  secondary 
or  reduced,  in  CgHg  and  CeH^o  partially  reduced. 

These  hydrogen  addition  products,  also  called  hydrocarhocydic 
compounds,  such  as  hexahydrotoluene,  CeHnCCHj),  hexahydroxylene, 
C6Hj„(CH3)2,  form  with  the  naphthenes  (see  below)  Caucasian  petroleum. 
Most  of  them  may  be  transformed  into  the  corresponding  isocyclic 
compound  by  oxidation.  These  addicion  products  with  their  respect- 
ive derivatives  differ  markedly  from  their  mother-substances,  as  they 
behave  like  the  aliphatic  compounds  and  hence  belong  to  the  ahcyclic 
compounds  (p.  327) ;  still  in  order  to  make  the  subject  clear  they  will 
be  treated  in  connection  with  their  mother  substances. 

For  example,  di-  and  tetrahydrobenzene,  Q^^  and  CgH^o,  as  well  as 
their  derivatives  which  still  contain  a  few  C  atoms  with  double  bonds, 
behave  like  the  corresponding  unsaturated  aliphatic  compounds.  Hexa- 
hydrobenzene,  CgHij,  which  contains  the  C  atoms  all  with  single  bonds, 
behaves,  with  its  derivatives,  like  a  saturated  aliphatic  compound  (see 
below).  The  most  important  compounds  of  this  class  are  those  of  the 
terpene  group,  which  will  be  considered  later. 

Closely  related  to  the  isocarbocyclic  compounds  and  forming  a  con- 
nection with  the  aliphatic  compounds  we  have  those  alicvclic  compounds 
which  form  the  simplest  constituted  compounds  with  C  rings,  namely, 
the  polymethylencs  or  naphthenes,  which  consist  of  three  or  more  methylene, 


464  ORGANIC  CHEMISTRY. 

groups,  -CHg",  or,  as  they  are  isomerides  of  the  defines,  they  are  also 
called  cyclo-olefines;  e.g., 

Trimethylene.  Tetramethylene.  Pentamethylene. 

<H2  HgC^CHg  yH2C~CH2 

H2  H2C-CH2  '   \H2C-CH2 

Hexamethylene,  CgHij,  is  identical  with  the  above-mentioned  hexahydro- 
benzene,  C6H6(H)e  (p.  463). 

They  form  the  chief  constituents  of  Caucasian  petroleum  (p.  341), 
and  also  occur  in  coal-tar  and  shale-oil,  and  in  the  resin-oil  obtained  in  the 
distillation  of  colophonium.  They  behave  like  saturated  aliphatic  com- 
pounds, and  differ  from  the  isomeric  olefines  by  their  inability  of  forming 
addition  products  and  their  stability  towards  KMn04. 

The  acids  of  these  hydrocarbons  also  occur  in  petroleum  and  are 
called  petrolic  adds;  e.g.,  C6H,o(CH3)(COOH).  These  acids  are  isomer- 
des  of  tlie  oleic  acids,  but  cannot,  like  these,  be  converted  into  fatty  acids. 

SUBSTITUTION. 

The  most  essential  difference  between  the  aliphatic  and  cyclic 
compounds  is  shown  by  substitution. 

In  the  aliphatic  hydrocarbons  the  hydrogen  can  only  be  directly 
replaced  by  other  elements  with  difficulty.  The  halogens  only  have  the 
power  of  expelling  the  hydrogen  and  of  taking  its  place;  hence  these 
compounds  are  used  in  order  to  obtain  new  derivatives.  In  the  cyclic 
hydrocarbons  and  their  derivatives,  on  the  contrary,  the  hydrogen 
of  the  benzene  ring  can  not  only  be  directly  replaced  by  the  halogens 
with  ease,  but  also  by  the  action  of  nitric  acid  or  sulphuric  acid, 
whereby  the  nitro  group,  "NOz,  or  sulphonic  acid  group,  "SOgH, 
replaces  the  hydrogen,  e.g., 

CeH«+HO-SOrOH  =CeH5-SO,OH-f-H20. 

Benzene.     Sulphuric  acid.     Benzenesulphonic  acid. 

CJH.+2gg>S0,  -C.H.<|§Cgg+HA 

Benzene  disulp ho nic  acid. 

CeHe+  HO-NO3  =  CeH5-N02+  Bfi. 
Nitric  acid.      Nitrobenzene. 

CeH50H+  HO-SO3-OH  =  C«H,(OH)  (SO3H)  +  HA 

Phenol.  Sulphuric  acid.       Phenolsulphonic  acid. 

C350H+HO-NO,  =  CeH,(OH)-(N02)  +  H20. 

Phenol.        Nitric  acid.  Nitrophenol. 

These  sulphonic  acid  and  nitro  compounds  are  isomeric  with  the 
sulphurous  acid  and  nitrous  acid  compounds.     Still  in  the  sulphonic 


SUBSTITUTION.  465 

acids  and  nitro  bodies  the  sulphur  or  the  nitrogen  is  directly  united 
to  the  carbon  atom,  while  in  the  sulphites  and  nitrites  the  binding 
takes  place  through  the  oxygen  atoms:  C2H5~0~SO~OH,  ethyl 
sulphite;  C2H5~ONO,  ethyl  nitrite  (differentiation  by  nascent  hydro- 
gen, see  p.  319). 

That  portion  of  the  benzene  molecule  remaining  after  substitution 
is  called  the  benzene  nucleus. 

With  the  aliphatic  bodies  the  sulphuric  acid  and  nitric  acid  act  only 
upon  the  alcohols  or  unsaturated  hydrocarbons  and  form  esters  with  them 
(pages  357  and  395);   e.g., 

aH^OH  +  HO-SO^-OH = C^H. -O-SO^-OH  +  H^O. 

Ethyl  alcohol.  Ethyisulphuric  acid. 

The  sulphonic  acid  and  nitro  compounds  of  the  aliphatic  compounds 
can  only  be  obtained  in  an  indirect  manner;  thus,  by  the  action  of  the 
alkyl  iodides  upon  silver  sulphite  or  nitrite: 

AgN02+  C^H.I  =CA-N02  +  AgI; 

Ag^SOg  +  2C2H,I= C,H3-S0,-0-C,H,  +  2  Agl. 

Ethyl  sulphonic  acid  ethyl  ester. 

On  heating  the  last  ester  with  water,  alcohol  is  split  off  and  an  aliphatic 
sulphonic  acid  is  obtained. 

The  union  of  the  halogen  atoms  in  the  benzene  ring  is  much 
firmer  than  in  the  open  C  chain  of  the  aliphatic  compounds,  so  that  they 
generally  cannot  be  replaced  by  other  groups  by  double  decomposition. 

A  polyvalent  element  never  replaces  several  hydrogen  atoms  in 
one  benzene  molecule,  therefore  compounds  like  C6H4"'0  or  CeHg  — N 
are  unknown.  On  the  contrary,  a  polyvalent  radicrl  can  replace 
several  H  atoms  in  a  benzene  molecule  (see  Terpenes  and  Alkaloids). 
The  amido  bodies  are  obtained  from  the  nitro  bodies  by  reduction 
(by  nascent  hydrogen): 

CeH5N02+  6H  =  CeH5NH2+  2H2O. 

In  this  reduction  azo  compounds  (azote  =  nitrogen)  appear  as 
intermediate  products.  They  contain  the  divalent  group  ~N^N~, 
consisting  of  two  trivalent  N  atoms,  which  is  united  by  both  valences 
with  two  cyclic  radicals. 

Closely  related  to  these  we  have  the  diazo  compounds  which  con- 
tain the  group  "'N=N,  consisting  of  one  pentavalent  and  one  tri- 
valent N  atom,  which  is  united  with  only  one  valence  with  one  C 
atom  of  one  cyclic  radical;  e.g., 

CeH5-N=N-CeH5  (NO3)  (C,H5)=N-N 

Azobenzene.  Diazo  benzene  nitrate. 


466  ORGANIC  CHEMISTRY. 

If  the  hydrogen  atoms  of  the  benzene  ring  of  benzene  and  its  deri- 
vatives are  replaced  by  hydroxyl  groups,  we  obtain  the  phenols  which 
are  comparable  with  the  alcohols  (p.  474) : 

CeHsCOH),  CeH,(OH)„  CeH3(OH)3. 

The  phenols  contain,  like  the  tertiary  alcohols,  the  group  —  C~OH 
(p.  334)  and  do  not  yield  aldehydes,  ketones,  and  acids  on  oxidation, 
as  the  C  atom  of  this  group  is  only  monovalent: 

H  H  H 

C  C  C 

^\  ^\  ^\ 

HC     CH  HC     C(OH)  HC     C(OH) 

I      II  I      II  I      II        - 

HC     C(OH)  HC     C(OH)  HC     C(OH) 

\/  \/  \y 

c  c  c 

H  H  (OH) 

Phenol.  Pyrocatechin.  Pyrogallol. 

On  replacing  the  H  atoms  in  benzene  consecutively  by  alkyls  we 
obtain  homologues  of  the  benzene  hydrocarbons  which  are  richer  in 
carbon  (p.  472) : 

Methyl  benzene,       CgHsCCHj); 

Dimethyl  benzene,  C6H4(CH3)2; 

Trimethyl  benzene,  C6H3(CH3)3,  etc. 

In  these  compounds  as  well  as  their  derivatives  (see  Isomerism) 
the  benzene  residue  retains  the  properties  of  the  benzene  and  can  be 
readily  replaced  by  halogens,  "NOa,  ~S03H,  etc.  On  the  other  hand, 
the  aliphatic  side  groups  behave  in  a  manner  similar  to  the  aliphatic 
hydrocarbons. '  While,  for  example,  the  halogen  atoms  contained 
in  the  benzene  nucleus  are  very  firmly  united,  those  in  the  side  chain 
behave  similar  to  the  aliphatic  derivatives,  and  we  can  therefore 
readily  replace  them  by  monovalent  groups.  All  the  homologues  of 
benzene,  on  the  contrary,  can  be  readily  oxidized  into  benzene  car- 
boxyl  acids  in  contradistinction  to  the  paraffins  (p.  473). 

ISOMERISM. 

On  substitution  either  in  the  benzene  ring  or  in  the  side  chains  we 
obtain  two  series  of  isomeric  compounds.  For  example,  from  methyl 
benzene  or  toluene  the  following  series  of  isomers  are  derived : 


ISOMERISM.  467 

Monochlortoluene,  C6H4C1~CH3;        Benzyl  chloride,  C6H5~CH2C1; 
Cresol,  C6H,(OH)-CH3;  Benzyl  alcohol,  CgHs-CHrCOH). 

If  the  hydrogen  atoms  of  the  aliphatic  side  chain  are  replaced  by 
hydroxyl,  we  obtain  true  alcohols  of  the  benzene  series,  which  on 
oxidation  yield  aldehydes,  ketones,  and  acids : 

C,HrCH„  CeH5-CH,0H,         C„H5-CH0,         CoH,rCOOH. 

Methyl  benzene.  Benzyl  alcohol.  Benzaldehyde.  Benzoic  acid. 

Substitution  in  the  nucleus  is  indicated  as  endo-substitution,  and  in 
the  side  chain  as  exo-;  thus,  endochlortoluene,  CgH^Cl-CHg,  and  exochlor- 
toluene,  C6H5~CH2C1;  (o-  denotes  substitution  at  the  last  C  atom  of  the 
side  chain  (C8H5-0H2~CH2C1,  6>-chlorethyl  benzene),  while  a-,  /?-,  etc., 
denote  substitution  at  the  succeeding  C  atoms;  thus,  CeH5-CH2~CHCl~CH8 
is  a-chlorpropyl  benzene). 

From  this  it  follows  that,  by  substitution  in  the  benzene  ring  or 
in  the  side-chain,  we  may  have  a  great  variety  of  benzene  derivatives, 
and  the  number  becomes  still  greater  on  account  of  the  isomerism 
possible  on  account  of  the  structure  of  benzene. 

If  any  hydrogen  atom  in  the  benzene  molecule  is  replaced  by  an- 
other atom  or  an  atomic  group,  each  compound  thus  obtained  can 
only  exist  in  one  modification.  Hence  we  have  only  one  chlorbenzene, 
one  nitrobenzene,  one  methyl  benzene,  etc.  The  6  H  atoms  of  benzene 
have  the  same  value,  depending  upon  their  mutual  position. 

If,  on  the  contrary,  two  hydrogen  atoms  of  the  benzene  are  replaced 
by  two  similar  or  different  monovalent  atoms  or  atomic  groups, 
then  it  follows  that  three  modifications  of  such  a  compound  are  possible, 
and  in  fact  all  three  theoretically  possible  isomers  of  most  com- 
pounds are  known  and  are  designated  as  follows : 

Ortho  and  Meta      and        Para  compounds. 

CH3  CH3  CH3 

^1\  A\  ^1\ 

H-Ce   2C-CH3  H-Ce    2C-H  H-Ce    2C-H 

H-C5,3C-H  H-C5,3J-CH3      ""     H-C5,3C-H 

•     \o/  \y  ^C^ 

If,  for  example,  we  admit  that  two  CH3  groups  are  substituted  for 
2  H  atoms,  then  these  methyls  take  the  following  positions  if  we 
number  the  C  atoms  from  1  to  6  as  above :    (a)  1 : 2,  {b)  1 : 3,  (c)  1: 4. 


(a) 


468  ORGANIC  CHEMISTRY. 

Other  positions  are  not  possible,  as  position  1:6  is  the  same  as  a, 
and  1 : 5  the  same  as  h. 

In  the  ortho  compounds  the  neighboring  hydrogen  atoms  are  sub- 
stituted (position  1:2  or  1:6). 

In  the  meta  compounds  a  hydrogen  atom  exists  between  the  sub- 
stituted hydrogen  atoms  (position  1 :3  or  1 :5). 

In  the  para  compounds  two  H  atoms  exist  between  the  substi- 
tuted H  atoms;  that  is,  two  opposite  hydrogen  atoms  are  substituted 
(position  1:4  or  2:5  or  3:6). 

We  designate  these  isomerides  by  prefixing  o-,  m-,  p-,  or  1*2,  1  •  3, 
1-4  to  the  formula;  thus,  P-C6H4CI2  or  1-4  CeH^Clj  is  paradichlor- 
benzene. 

These  isomers  are  also  called  position  or  nucleus  isomers  (p.  302). 
Those  isomers  which  are  obtained  by  substitution  once  in  the  benzene 
ring  and  another  time  in  the  side-chain  are  called  mixed  isomers; 
thus,  CgH^Br-CHg  and  CgHgCHgBr.  Isomers  produced  by  substitution 
in  the  side-chain  are  called  side-isomers;  e.g.,  CftH^-CHg" CHgCl  and 
CeH-CHCl-CHg. 

By  various  chemical  operations,  for  example,  oxidation,  further  sub- 
stitution, condensation,  etc.,  it  is  possible  to  determine  the  relative  posi- 
tion of  the  substituted  groups  in  the  benzene  ring.  It  follows  that  mesity- 
lene,  CcH3(CH)3,  has  a  systematic  structure,  i.e.,  the  methyl  groups  have 
the  position  1:3:5,  because  mesitylene  is  formed  by  condensation  from 
3  molecules  of  acetone.  If  we  heat  acetone,  CH3-CO-CH3,  with  sulphuric 
acid,  O  and  Hg  are  removed  as  water,  and  three  residues  =C(CH3)-CH=" 
unite,  forming  mesitylene  just  similar  to  the  condensation  of  3  mol.  acety- 
lene, forming  benzene: 

CHoH  CH,    H     CH,    H    CHv    H 

311=1  11  II  I 

=c — c=  c c=c c=c c 


The  ortho  compounds  are  characterized  by  readily   forming  from  one 
molecule  so-called  internal  anhydrides  on  splitting  off  of  water: 

o-amidophenyl  acetic  acid.  Oxindol. 

^«^*<N?I~^^^^     yields     CeH,<^^>COH  +  HA 
Isatinic  acid.  Isatin. 

Many  derivatives  of    orthophenylendiamine,  for  example,  the  acetyl, 
propionyl,  benzoyl,  etc.,  derivatives,  yield  benzenediazoles  (which  see): 

Acetyl-o-phenylendiamine.  Ethenylphenylenamidine. 


ISOMERISM, 


469 


From  the  first  two  processes  it  follows  that  the  splitting  off  of  HgO 
from  o-amido  acids  takes  place  where  only  one  H  atom  of  the  NHg  group 
goes  out  with  the  OH  group,  which  is  designated  as  lactame  formation,  or 
both  H  atoms  of  the  NHj  group  are  taken  away,  which  is  called  lactime 
formation. 

If  three  or  four  hydrogen  atoms  of  benzene  are  replaced  by  equiva- 
lent atoms  or  radicals,  then  necessarily  three  isomers  are  possible, 
while  if  five  or  six  hydrogen  atoms  6i  benzene  are  substituted,  only  one 
modification  is  possible;  thus  we  have  only  one  pentachlorbenzene, 
CeHCls,  and  one  hexachlorbenzene,  CeCle,  etc. 

The  isomers  of  the  tri-  and  tetra-substitution  products  are  designated 
by  V  {vicinus,  neighboring),  s  (symmetrical),  a  (asymmetrical).  The  fol- 
lowing figures  show  the  relative  positions  of  substitution: 


If  the  3,  4,  etc.,  substituted  atoms  or  radicals  are  different,  then  the 
possible  isomers  are  still  greater;  thus,  six  isomers  of  the  formula 
C6H3(X)2(Y)  and  ten  isomers  of  the  formula  C6H3(X)(Y)(Z)  are  pos- 
sible. 

As  with  the  corresponding  bi-derivatives  (p.  467),  the  C  atoms  of  the 
benzene  nucleus  are  numbered  from  1  to  6,  and  the  group  containing 
the  atom  having  the  smallest  atomic  weight  united  directly  with  the 
nucleus,  occupies  the  position  1.  The  remaining  substituted  groups  are 
further  indicated  in  their  order,  so  that  the  increased  atomic  weight  of 
the  atoms  directly  united  with  the  nucleus  is  shown.  If  two  equal  atoms 
are  united  with  the  nucleus,  then  the  other  atoms  of  the  group  are  con- 
sidered according  to  their  atomic  weights. 

With  several  side-chains  containing  carbon  the  one  which  causes  the 
least  increase  in  molecular  weight  takes  first  place;  for  example, 


OH 


OH 


Br        CI 


OCH3 


)l  OCH3 

Chlorbromphenol     Chlorbromphenol         Amino-oxymethoxy-       Oxymethoxychlor- 
1-3-4.  l-4*5.  nitrobrombenzene  I'S^S  6.       benzene  1'3*6. 


470  ORGANIC  CHEMISTRY. 

With  the  alicyclic  compounds  (p.  327)  the  number  of  isomers  is  often 
still  greater  as  soon  as  the  mutual  position  of  the  double  bonds  is  taken 
into  consideration. 

In  order  to  designate  the  position  of  the  double  bonds,  J  with  the 
number  of  the  C  atoms  where  the  double  bonds  exist  is  placed  before  the 
name  of  the  substance;  thus,  dihydrobenzene,  p.  463,  J'2-6  (arrangement 
of  the  C  atoms,  pp.  462  and  467). 

RELATIONSHIP     BETWEEN    ISOCARBQCYCLIC    AND    ALIPHATIC 

COMPOUNDS. 

The  formation  of  isocarbocyclic  compounds  from  aliphatic  ones  is 
possible  only  in  a  relatively  small  niunber  of  mstances,  and  is  designated 
as  nucleus  synthesis. 

Many  aliphatic  hydrocarbons  and  alcohols  when  passed  through  red- 
hot  tubes  in  the  form  of  vapor  yield  isocarbocyclic  compounds;  thus, 
methane,  ethyl  alcohol  and  acetylene  yield  benzene,  CeHg.  On  distilling 
allylene  with  dilute  sulphuric  acid  we  obtain  mesitylene:  3C3H^= 
CeH3(CH3)3,  and  the  same  from  acetone:  3C3H60=C6H3(CH3)3  +  3H20. 
In  the  same  manner  many  homologues  of  acetylene,  also  many  ketones, 
ketone  aldehydes,  ketonic  acids,  ketonic  acid  esters,  and  aldehyde  acids 
yield  isocarbocyclic  compounds. 

In  sunlight  propiolic  acid  yields  trimesic  acid:  3C3H202=C8H3(COOH)3; 
bromacetylene  yields  tribrombenzene  under  the  same  conditions: 

3C2HBr=CeH3Br3. 

On  the  oxidation  of  wood  charcoal  or  graphite  we  obtain  mellitic  acid 
C8(COOH)e,  and  by  the  action  of  CO  upon  K  with  heat  hexaoxybenzene 

Eotassium,  CjCOK),,  isformed  (p.  189),  Triethylphloroglucin  is  obtained 
y  the  action  of  AICI3  upon  butyryl  chloride:  3CH3-CH2-CH2-C0C1= 
C8H3(0'C2H6)3+3HC1;  and  by  the  action  of  potassium  bisulphate  upon 
geranial  we  obtain  cymene:  C,oHi60=C8H4(CH3)(C3H7)  +  H20.  The 
formation  of  aliphatic  compounds  from  isocarbocyclic  compounds  is 
known  only  in  a  few  instances. 

Most  of  the  isocarbocyclic  compounds  are  very  resistant  towards  the 
action  of  high  temperatures.  When  benzene  is  passed  through  red-hot 
tubes  it  yields  acetylene  in  part,  and  as  this  latter  also  forms  benzene  it  is 
possible  that  both  reactions  must  proceed  until  an  equilibrium  is  estab- 
lished. 

Nevertheless  it  is  possible  to  rupture  the  benzene  ring  (especially  the 
phenols,  quinones,  and  their  derivatives)  by  chemical  means.  In  these 
cases  alicyclic  intermediary  products  are  produced,  and  these  are  isolated 
with  difficulty. 

On  strong  oxidation  compounds  with  1  and  2  C  atoms  are  produced,  for 
example  CO2,  formic  acid,  oxalic  acid,  while  on  milder  oxidation  (dilute 
KMnOi  solution)  phenol,  C8H5(OH),  is  converted  into  mesotartaric  acid, 
C4H8O8,  and  oxalic  acid,  while  pyrocatechin,  C6H4(OH)2,  and  dioxyben- 
zoic  acid,  C8H3(OH)2(COOH),  are  oxidized  by  HNO2  into  dioxytartaric 
acid,  C,H808  (=C4H208  +  2H20). 

On  treatment  with  chloric  acid  a  simultaneous  oxidation  and  chlorina- 
tion  takes  place.  Thus  from  benzene  we  obtain  trichloracetylacrylic  acid, 
CCl3-C0-CH=CH-C00H  (p.  440),  from  phenol,  CcH5(0H),  or  salicylie 


NOMENCLATURE.  471 

acid,  C,H4(0H)(C00H),  trichlorpyroracemic  acid,  CCI3-CO-COOH  (p. 
428),  and  chlorpicrin,  CClgCNOj),  from  picric  acid,  C6H2(OH)(N02)3. 

Chlorine  often  acts  in  a  similar  manner.  Di-  and  trioxybenzenes  are 
converted  by  chlorine  into  chlormated  aliphatic  acids  or  ketones  with  4 
and  5  C  atoms;  thus,  resorcin,  CeH4(OH)2,  is  converted  into  pentachlor- 
glutaric  acid,  HOOC-CCI2-CHCI-CCI2-COOH  (p.  425). 

By  reduction  (nascent  H)  from  the  phenolcarboxyl  acids,  for  example 
from  salicylic  acid,  CeH4(0H)(C00H),  and  its  derivatives,  we  obtain 
pimelic  acid,  HOOC-(C^.2)5~COOH,  and  its  derivatives.  Dihydro- 
resorcin,  C6H4(OH)2H2,  yields  acetylbutyric  acid,  CHg-CO-CHg-^Ha-CHa- 
COOH,  when  heated  with  Ba(0H)2.  Benzene  yields  hexane,  C^^xn  when 
heated  to  280°  for  a  long  time  with  HI. 

The  formation  of  alicyclic  compounds  (p.  327)  with  6  C  atoms  in  the 
ring  may,  corresponding  to  their  intermediary  position,  take  place  either 
from  the  aliphatic  or  from  the  isocarbocyclic  compounds. 

To  these  belong  the  addition  products  of  benzene  and  their  derivatives,  of 
which,  for  example,  hexahydrobenzene,  C6Hj2,  can  be  produced  by  the 
addition  of  H  to  benzene,  as  well  as  by  the  action  of  Na  upon  dibrompropane : 
2CH2Br-CH2-CH2Br4-  2Na=  2NaBr +  C6Hi2.  The  polymethylenes  (p.  463) 
also  belong  to  the  alicyclic  compounds,  also  certain  aliphatic  compounds 
with  ring-shaped  closed  atoms  closely  related  to  the  heterocyclic  com- 
pounds (which  see). 

NOMENCLATURE. 

The  nomenclature  of  the  isocarbocyclic  compounds  corresponds 
in  general  with  that  of  the  aliphatic  compounds.  The  differences  as 
well  as  the  designation  of  certain  groups  not  mentioned  in  connection 
with  th-e  aliphatic  compounds  have  been  given  in  the  preceding 
pages.  In  regard  to  the  significance  of  the  letters  a-,  [i-,  oj-,  etc.,  see 
p.  467;  of  0-,  m-,  p-,  see  p.  468;  of  s-,  a-,  v-,  see  p.  469;  of  i,  see  p. 
470.  In  regard  to  the  meaning  of  1-2,  1-3,  1-4,  see  p.  468,  and  of 
exo-  and  endo-,  see  p.  467. 

The  radical  "CgHs  is  called  phenyl,  CeHs'CHj,  benzyl,  etc.  The 
monovalent  isocarbocyclic  hydrocarbon  radicals  are  called  alphyles. 

CLASSIFICATION. 

In  the  following  pages  those  compounds  \vith  one  benzene  ring  will 
be  considered  in  special  groups  according  to  the  number  of  aliphatic 
hydrocarbons  introduced;  at  the  same  time  those  compounds 
standing  in  close  genetic  relationship  to  them  will  also  be  considered. 
After  this  the  compounds  containing  several  benzene  rings  will  follow, 
each  divided  into  groups  according  to  the  mutual  binding  of  the 
benzene  rings.  Then  follow  the  alicyclic  terpene  groups,  and  finally 
those  compounds  belonging  to  the  group  of  glucosides,  bitter  principles, 


472 


ORGANIC  CHEMISTRY. 


and  coloring  matters  which,  on  account  of  their  not  sufficiently  known 
constitution,  cannot  be  placed  in  the  other  groups. 


THE  MOST  IMPORTANT  ISOCARBOCYCLIC  COMPOUNDS   IN 
GENERAL. 


Benzene, 

Toluene, 

Xylenes, 

Mesitylene, 

Pseudocumene, 

Hemimellitene, 

Durene, 

Isodurene, 

Prehnitene, 

Pentamethyl  benzene, 

Hexamethyl  benzene, 


I.  Hydrocarbons. 

General  formula  CnH2n-6. 
CeHg.  — 

C6H,(CH3). 

C6H4(CH3)2 


CeH3(CH3), 


CeH,(CH3),. 

CeH(CH3),. 
C6(CH3)e. 


Ethyl  benzene,       C,R,(Cja.,). 

Propyl  benzenes,  CaB.^(CJi.j). 

Butyl  benzenes,    C6H5(C4H9). 
Cymene,  CflH<<^'^3 

Amyl  benzenes,     C^R^iCjiji). 
Triethyl  benzenes,  CeHgCCgHg^g. 

In  these  homologues  of  benzene  the  isomers  differ  chiefly  in  their 
boihng-points,  as  well  as  in  their  behavior  on  oxidation  (p.  473). 

The  unsaturated  benzene  hydrocarbons  are  derived  from  the  poly- 
valent hydrocarbons  of  the  olefine  and  acetylene  series,  etc.,  in  which 
hydrogen  is  replaced  by  the  phenyl  radical,  CgHg,  or  derivatives  of  the 
same;  e.g.,  C6Hs-CH=CH2,  phenyl  ethylene;  CeHs-C  CH,  henyl  acety- 
lene. These  are  readily  transformed  into  saturated  compounds  by  addi- 
tion. 

Occurrence.  Many  occur  in  coal-tar.  Benzene,  toluene,  and  their 
hydrogen  addition  products  (p.  463)  occur  with  naphthenes  (p.  464);  also 
in  Caucasian  petroleum. 

Formation.  1 .  By  the  action  of  sodium  upon  a  mixture  of  bromben- 
zenes  and  alkyl  bromides  (p.  340,  i) : 

CeHgBr  +  CR.Bt  +  2Na= CeHsCCHg)  +  2NaBr; 
CeH^Br-CHg  +  CHaBr  +  2Na  =  C6H,(CH3)2  +  2NaBr. 

2.  By  the  action  of  alkyl  chlorides  upon  isocyclic  hydrocarbons  in  the 
presence  of  anhydrous  aluminium  chloride  (Friedel-Craft's  synthesis,  p. 
320): 

CeHe  +  CH3CI  =  CeHs-CHg  +  HCl. 

3.  From  diazo  compounds  (which  see)  by  heating  with  alcohols. 

4.  On  the  dry  distillation  of  the  corresponding  isocyclic  acid  with 
caustic  lime  (p.  340,  2) : 

CfiHsCOOH  +  CaO = CeH,  +  CaCOg. 

Benzoic  acid.  Benzene. 

5.  On  the  dry  distillation  of  various  non-volatile  carbon  compounds, 
such  as  wood,  resin,  bituminous  shale,  and  especially  coal.  They  are  also 
produced  from  volatile  fatty  bodies  (such  as  methane,  alcohol,  ether, 
petroleum)  when  their  vapors  are  passed  through  red-hot  tubes. 


HYDROCARBONS.  473 

Preparation.  They  are  chiefly  obtained  on  a  large  scale  from  coal-tar 
(p.  323),  which  contains  over  40  cyclic  compounds  and  also  a  few 
aliphatic  compounds.  They  are  separated  therefrom  by  fractional  dis- 
tillation. 

Coal-tar  can  be  separated  by  fractional  distillation  into  the  following 
four  parts: 

a.  The  light  oil,  having  a  specific  gravity  of  0.8-0.9,  contains  the 
products  boiling  below  170°,  and  consists  chiefly  of  benzene,  indene, 
styrene,  toluene,  xylene,  trimethylbenzene  pyridine,  and  thiophene. 

h.  The  middle  or  carbolic  oil,  sp.  gr.  0.9-0.98,  boiling  between  170° 
and  230°,  consists  chiefly  of  phenol,  cresols,  aniline,  naphtlialene,  and 
quinoline  bases. 

c.  The  heavy  oil,  which  sinks  in  water  and  boils  between  230°  and  270°, 
contains  cresols,  xylenoles,  pyridine  and  quinoline  bases,  and  about  50 
per  cent,  naphthalene. 

d.  The  anthracene  oil,  boiling  above  270°,  contains  acenaphthene, 
anthracene,  phenanthrene,  pyrene,  chrysene,  etc.,  and  is  used,  under  the 
name  carbolineum,  as  a  preservative  agent  for  wood. 

Properties.  Durene,  penta-  and  hexamethyl  benzene  form  color- 
less crystals,  while  the  others  are  colorless  liquids  which  are  volatile 
without  decomposition,  and  insoluble  in  water  but  soluble  in  alcohol 
and  ether.  They  have  a  peculiar  odor  and  burn  with  a  smoky  flame. 
With  sulphuric  acid  they  yield  sulphonic  acids  (p.  464)  and  nitro 
bodies  with  nitric  acid  (p.  464),  and  with  nascent  hydrogen  they 
are  transformed  into  hydrocyclic  compounds.  As  the  homologues 
of  benzene  contain  alkyls,  they  have  the  properties  of  the  aliphatic 
compounds  as  well  as  of  the  cyclic  compounds,  and  may  also  yield 
the  corresponding  derivatives  (p.  467).  Although  the  isomers  of  the 
benzene  hydrocarbons  are  very  similar  in  behavior,  still  they  are  readily 
differentiated  by  oxidation,  as  in  this  operation  the  benzene  remains 
unchanged,  while  each  aliphatic  side-chain  is  transformed  into  a 
carboxyl  group  irrespective  of  the  number  of  C  atoms  existing  therein. 

1  '^^Vf  "^^*rV^  benzene,  CeH^-CH,,  ethyl  benzene,  CeH^-C^Hs,  amyl  ben- 
zol, CeHg-CsHi,,  phenyl  ethylene,  C^^Yi^-Q^B.^,  etc.,  yield  the  same  mono- 
carbonic  acid,  CgHg-COOH  (benzoic  acid). 

Dimethyl  benzene,  CeH^CCH.,)^,  diethyl  benzene,  CbH.CC^H,)^,  methvl 
PrpPyl  benzene^  CeH,(CH3)(C3H,),  etc.,  yield  the  corresponding  dicarbonic 
acid,  CeH.CCOOH)^  (phthalic  acid,  p.  476),  etc.     i 

As  the  halogens  act  upon  the  benzene  nucleus  as  well  as  upon  the 
side-chain,  we  obtain,  according  to  conditions,  isomers  which  have  en- 
tirely different  properties  (p.  467).  While  the  halogen  in  the  side-chain, 
as  in  all  aliphatic  compounds,  is  readily  replaceable,  those  in  the  benzene 
nucleus  are  very  firmly  combined  and  cannot  be  removed  by  either 


474  ORGANIC  CHEMISTRY. 

alcoholic  or  aqueous  caustic  potash,  nor  by  silver  salts  or  ammonia, 

but  only  by  metaUic  sodium  or  nascent  hydrogen. 

Substitution  in  the  benzene  nucleus  takes  place  when  halogens  act 
thereon  in  the  cold  with  the  exclusion  of  direct  sunlight  or  in  the  pres- 
ence of  iodine.  These  products  have  an  aromatic  odor  and  their  vapors 
do  not  irritate  the  eyes  or  nose.  According  to  the  length  of  action  of  the 
halogens,  the  hydrogen  is  in  part  or  entirely  substituted:  CeHjBr,  CgH^Cla, 

CftHglg,  C6H2I4. 

Substitution  in  the  side-chain  occurs  by  the  action  of  halogens  in  the 
warmth  or  in  cold  with  direct  sunlight  (without  the  addition  of  iodine). 
These  products  have  a  pungent  odor,  and  the  vapors  cause  great  irritation 
of  the  eyes  and  nose. 

With  benzene  itself,  independent  upon  temperature,  the  formation  of 
addition  products  (p.  463)  always  takes  place  in  direct  sunlight  with  the  for- 
mation of  CgHeCla,  C6HeCl4,  and  finally  CeHeClg.  In  diffused  sunlight  or  in 
the  presence  of  iodine  substitution  products  are  produced.  The  iodine 
derivatives  are  only  obtained  in  the  presence  of  oxidizing  bodies,  especially 
HgO  and  HIO3,  which  destroy  the  HI  produced  (p.  322). 

In  regard  to  the  formation  of  the  benzene  halogens  from  the  phenols 
see  page  475. 

a.  Phenols. 

a.  Monohydric  Phenols.  b.  Dihydric  Phenols. 

Benzophenol,         CeHjOH.  Hydroquinone,  ) 

Cresols,  C8H,(CH3)(OH).  Pyrocatechin,     ^CeH^COH)^. 

Xylenols,  C6H3(CH3)2(OH).  Resorcin,  J 

Ps^idocumenol,  [  C6H2(CH3)3(OH) .  Ho^^opyrocate-  [  CeH3(CH3)  (OH),. 
Durenols,               C6H(CH3)4(OH).  chin,  ) 

Thymol,  lcH<r^^3rOH^  Dioxyxyhnes,      C6H2(CH3)2(OH)2. 

Carvacrol,  f '"ens^Q^jj^^un;.  ^^^^^^^^^  C8H(CH3)3(OH)2. 

%Tenot''        [CeH(C3).(0H).         ^''IZX"  l''^^''''^^^''^''^^^'''^^- 

c.  Polyhydric  Phenols. 

Pyrogallol,  )  Methylpyrogallol,   C6H2(CH3)(OH)3. 

Oxy hydroquinone,  [•C6H3(OH)3.     Tetrao xy benzenes,  C6H2(OH)4. 
Phloroglucin,  )  Hexaoxybenz3ne,    Ce(0H)8. 

Properties.  The  benzene  compounds  with  the  hydroxyl  substituted  in 
the  benzene  ring  are  not  called  alcohols,  but  phenols,  as  they  differ  essen- 
tially from  the  alcohols.  (True  alcohols  of  the  benzene  series,  see  pages  467 
and  475.)  The  phenols  cannot  be  oxidized  to  the  corresponding  aldehydes 
and  acids  (p.  466).  They  are  colorless  liquids  or  solids,  generally  char- 
acterized by  their  odor,  soluble  in  alcohol  and  ether,  some  readily  soluble 
in  water  and  others  with  difficulty,  and  can  be  distilled  without  decom- 
position. They  also  have  more  acid-like  properties  and  combine  readily 
with  metallic  oxides,  forming  salt-like  compounds.  Thus  phenol,  CeH^OH, 
dissolves  in  caustic  soda,  forming  sodium  phenylate,  CfiH,-ONa;  lead 
oxide  dissolves  in  phenol,  forming  lead  phenylate  (C6H.,0)pPb:  mercuric 
oxide  dissolves  in  phenol    forming  mercuric  phenylate,  (C8H,;0)2Hg. 

If  CI,  Br,  or  NO2  is  introduced  into  the  benzene  nucleus  besides  hydroxyl, 
we  obtain  compounds  which  behave  nearly  like  true  acids.    The  hydrogen 


I 


AROMATIC  ALCOHOLS.  475 

of  the  hydroxyl  can  be  readily  replaced  by  alcoholic  or  acid  residues, 
producing  mixed  ethers  or  esters: 

C,H,-0(CH,),     (C6H,0),C0,     or     (C,H,),C03. 

Methylphenol.  Phenyl  carbonic  acid  ester. 

On  heating  with  zinc  powder  the  phenols  are  converted  into  aromatic 
hydrocarbons :    C^HgOH  +  Zn  =  CbH,  +  ZnO. 

On  treating  the  phenols  with  nitric  or  sulphuric  acid  we  do  not  obtain 
the  corresponding  ester  as  with  the  alcohols :  Cj.H60H  -f  HN03=  CaHgNOj  + 
HjO,  but  obtain  instead  nitro  compounds  or  sulphonic  acids  of  the  phenols 
(p.  464): 

C,H,OH  +  HNO,= C,H,  <  gg^  +  np ; 

C.H,OH  +  H,SO,= C,H,  <  g^«H  +  H,0. 

The  phenols  exchange  their  hydroxyl  on  treatment  with  phosphorus 
chloride,  bromide,  and  iodide  for  chlorine,  bromine,  and  iodine: 

SCeH^OH  +  PCl3=  SCjH^Cl  +  H3PO3; 
while  on  the  other  hand  the  direct  action  of  the  halogens  causes  a  substi 
tution  of  the  hydrogen  of  the  benzene  ring;  e.g., 

CeHgOH  +  Cl2=  HCl  +  CeH,Cl-OH. 

The  halogen  acids  do  not  act  upon  the  phenols.  With  sulphuric  acid 
containing  nitrous  acid  the  phenols  give  an  intense  coloration  (Lieber- 
mann's  reaction). 

With  ferric  chloride  they  yield  a  blue,  green,  or  violet  coloration  as 
long  as  the  H  of  the  OH  group  is  not  substituted. 

Preparation.     1.  From  diazo  compounds,  by  heating  with  water. 

2.  By  fusing  the  sulphonic  acids  with  caustic  alkali: 

CcHs-SOgK  +  KOH = C,nr  OH  +  K2SO3. 

3.  On  the  dry  distillation  of  the  oxyacids  of  the  benzene  series  with 
caustic  lime: 

C,H,(OH)(COOH)  +CaO=CeH,-OH  +  CaC03. 

4.  The  halogen  derivatives  of  the  benzenes  are  not  attacked  by  alkali 
hydroxides  (p.  465) ;  but  if  nitro  groups  are  present  at  the  same  time,  then 
they  are  transformed  into  nitrophenols : 

CbH.CI-NOj + KOH = C8H,(OH)-N03 + KCl. 

3.  Aromatic  Alcohols. 

a.  Alcohols. 

Benzyl  alcohol,  C,H,(CH,OH)  or    C^gA 

Tolyl  alcohol,  C^,(CH3)(CH20H)  or    C«H,oO. 

Phenyl  ethyl  alcohols,  CeH5(CH„-CH,0H).  ^  „  ^ 

Phenyl  propyl  alcohol,  C.UJC.R  -CH.OH)  or    CaH.A 

Cumyl  alcohol,  C,H,(C3H,)(CH,0H)  or    C,„H,jO. 

Xylylene  alcohols,        C,ni{CllfiH)^  or    C^H^oOy 

b.  Alcohol  Phenols. 

Saligenin,  C,H,(0H)(CH30H)  or  C^HA. 

Protocatechuic  alcoliol,  CeH3(OH)2(CH20H)  or  C^HA- 

GaUic  alcohol,  C,H,(0H)3(CH,0H)  or  C^HA- 


476  ORGANIC  CHEMISTRY. 

c.  Unsaturated  Alcohols. 

Cinnamyl  alcohol,  CeH5(CH=CH-CH20H)     or    C^HioO. 

Preparation  and  Properties.  The  aromatic  alcohols  (p.  467)  corre- 
spond in  properties  and  preparation  to  the  aliphatic  alcohols  (see  also 
Benzyl  Alcohol  and  Benzaldehyde).  As  they  are  on  the  other  hand  benzene 
derivatives,  they  may  also  be  made  to  undergo  the  transformations  which 
are  common  to  benzene.  By  the  introduction  of  "OH  groups  into  the 
benzene  nucleus,  we  obtain  the  alcohol  phenols. 

4.  Aromatic  Acids. 

a.  Monobasic  Acids. 

Benzoic  acid,  CcH,(COOH)  or  C^HnOa. 

Phenylacetic  acid,  CeHgCCH^.COOH)  or  CsHgOa. 

Toluicacid,  CeH,(CH3)('C00H)  or  CgHA. 

^r^?c';Sc^dds,  [  C„H3(CH3).(COOH)  or  C^H.A- 

Ethylbenzoic  acids,  CbH.CC^Hs)  (COOH)  or  C^HjoO^. 

Phenylpropionic  acids,  C6li5(C2H,.COOH)  or  CgHioOa. 

Cumicacid,  C6H,(C3H7)(COOH)  or  CioH^A- 

b.  Dibasic  Acids. 

Phthalic  acids,    CflH.CCOOH)^  or    C.HeO,. 

X^Udic'adi,!    C,H3(CH..)(C00H),      or    C,HA 

Cumidicacid,      C6H2(CH3),(COOH)2     or    C.^HioO^. 

c.  Tri-  and  Multibasic  Acids. 


Trimesic  acid,         ) 

Trimellitic  acid,      '  CeHgCCOOH),    or    C^HeOj. 

Hemimellitic  acid,  ) 

Pyromellitic  acid- ) 

Prehnitic  acid,     '\  C^^^{C0O¥L)^    or    C.J^tO^, 

Mellophanic  acid,  ) 

Benzenepentacarbonic  acid,    CeHCCOOH)^     or    C,.,HflOi9. 

MeUiticacid,  C6(C00H)e        or    Ci^HeO,^. 

d.  Monobasic  Phenol  Acids. 


Oxy benzoic  acids,  C8H4(OH)COOH                  or    C^HA- 

(salicylic  acid,) 

Oxytoluic  acids,  CaH3(CH3)(OH)(COOH)      or    C.H.Oa. 

Dioxytoluic  acids,  C6H,(CH0/OH).(COOH)     or    03,0,. 

Oxymesitylenic  acid,  C6H:(CH3)2(0H)(C00H)     or    C.U,,,0.. 

Oxyphenylpropionic  acid,  CeH;(OH)(C2H4COOH)        or    C^B.,Jd^. 

(hydrocumaric  and  meUlotic  acid,) 

Dioxybenzoic  acids,  CeH3(OH)2(COOH)               or    C^HgO^. 

(pyrocatechuic  acid,) 

Orsellic  acid,  C,H2(CH3)(OH)2(COOH)     or    C,H804. 

Gallic  acid,  ) 

Pyrogallic  carbonic  acid,  \  CeH2(OH)3(COOH)               or    C^HA- 
Phloroglucin  carbonic  acid,  ) 


AROMATIC  ACIDS.  477 

e.  Bibasic  Phenol  Acids. 

Oxyphthalic  acids,     CeH3(OH)(COOH)2       or    CsHeOg. 
Dioxyphthalic  acids,  C„H2(OH)2(COOH)2      or    CgHeOj. 

/.  Alcohol  and  Ketone  Acids. 

Mandelic  acids,  CgHsCCHOH-COOH)       or    CsH^Oa. 

Tropic  acid,  CeH5-CH<^g^^  or    C^Hi.O,. 

Phenyllactic  acid,      CeHgCC^HsOHCOOH)     or    C«H,„0,. 
Benzoylacetic  acid,   CoHg-COCCIia-COOH)    or    C^HgOa. 

g.   Unsaturated  Acids. 

Cinnamic  acid,  CeH5(CH=CH-C00H)  or    C^,P^ 

Atropicacid,  ^8^5C<™5jj  or    C^HsO^. 

Phenylpropiolic  acid,    CeH.CC^C-COOH)  or  C^HeO^. 

Oxycinnamic  acid,         C6H,(0H)(CH=CH-C00H)  or  CgH^O^. 

Dioxycinnamic  acid,     C6H3(OH)2(CH=CH-COOH)  or  C9H8O4. 

(caffeic  and  umbellic  acids,) 

Trioxycinnamic  acid,    C6H2(OH)3(CH=CH-COOH)  or  C^HgOg. 

Properties.  They  nearly  all  form  crystals  which  are  soluble  with 
difficulty  in  water,  and  hence  are  precipitated  from  the  solution  of  their 
salts  by  mineral  acids.  Those  with  simple  constitution  can  be  sublimed 
and  distilled,  while  the  others  generally  split  off  COg  on  heating.  Ihis 
cleavage  takes  place  with  all  of  them  on  heating  with  alkali  hy- 
droxides. In  other  respects  they  correspond  to  the  aliphatic  acids,  but  as 
they  are,  on  the  other  hand,  benzene  derivatives,  therefore  they  may  be 
made  to  undergo  the  transformations  which  are  common  to  benzene.  By 
the  introduction  of  HO  groups  into  the  benzene  nucleus  of  these  acids 
we  produce  phenol  acids,  also  called  oxyacids,  and  when  HO  groups  are 
introduced  in  the  side-chain  we  obtain  alcohol  acids  which  correspond  in 
most  properties  with  the  phenol  acids. 

Preparation.  1.  By  the  oxidation  of  the  corresponding  aldehyde  and 
primary  alcohol. 

2.  By  the  oxidation  of  the  homologues  of  benzene  (p.  473).  If  the 
homologues  also  contain  the  ~0H-,  NOg",  NH^,  groups,  etc.,  acids  with 
these  groups  are  obtained. 

3.  On  the  saponification  of  the  corresponding  nitrile;  e.g.,  CeH5CN  + 
2H2O = CeH^-COOII  +  NH3. 

4.  By  the  action  of  carbon  dioxide  derivatives  of  benzene  upon  certain 
benzene  derivatives  (see  Benzoic  Acid  and  Salicylic  Acid). 

5.  The  unsaturated  acids  are  obtained  according  to  Perkin's  reaction 
by  the  action  of  cyclic  aldehydes  upon  fatty  acids  (see  Cinnamic  Acid), 
also  from  the  monohalogen  derivatives  of  the  saturated  acids  by  means 
of  alcoholic  caustic  alkali  (p.  323). 

Occurrence.  They  occur  in  many  resins  and  balsams  and  as  NHg 
derivatives  in  the  animal  organism. 


478  ORGANIC  CHEMISTRY. 

COMPOXJNDS  WITH  SIX  CARBON  ATOMS  UNITED  TOGETHER. 
I.  Benzene  Compounds. 

Benzene,  CeHe,  benzol,  is  produced  from  most  organic  bodies  by 
Very  high  temperatures  and  hence  is  contained  in  coal-tar,  as  well 
as  small  amounts  in  illuminating-gas,  and  can  be  prepared  from 
acetylene  (p.  442).  It  is  produced  also  on  the  distillation  of  all 
benzene  carboxylic  acids  which  contain  only  COOH  side-groups,  with 
calcium  oxide.  Ordinarily  it  is  obtained  from  that  part  of  coal-tar 
boiling  between  80-85°  by  fractional  distillation  or  by  cooling.  It 
is  therefore  also  called  tar  or  coal  benzine,  in  contradistinction  to 
petroleum  benzine  (p.  341).  It  is  prepared  pure  by  distilling  ben- 
zoic acid  with  caustic  lime. 

CeH6-C00H+  CaO  =  C6H6+  CaCO,. 

It  is  a  colorless  refractive  liquid  boiling  at  80°  and  crystallizing 
at  0°.  It  is  readily  inflammable  and  burns  with  a  luminous  flame. 
It  is  insoluble  in  water,  soluble  in  alcohol  and  ether,  and  it  dissolves 
resins,  fats,  sulphur,  iodine,  phosphorus. 

Halogen  derivatives  of  benzene  (p.  473). 

Nitrobenzene,  C6H5(NO;;),  is  obtained  by  dropping  benzene  into 
fuming  nitric  acid.  If  water  is  added  to  this  mixture,  the  nitrobenzene 
precipitates  as  a  yellow,  poisonous,  heavy  liquid.  It  has  an  odor 
similar  to  bitter  almonds  and  hence  is  used  in  perfumery  as  oil  of 
Mirbane,  or  artificial  oil  of  bitter  almonds.  In  most  cyclic  nitro 
compounds,  as  well  as  in  the  aliphatic  compounds,  the  NOj  group 
is  not  replaceable  by  other  groups.  By  reducing  agents  the  nitro 
group  is  converted  in  acid  solution  into  the  amido  group: 
CeH5-N02+  6H  =  CeH5-NH,-i-  2H2O. 

In  neutral  solution  hydroxylamins  are  obtained,  and  in  alkali  solution 
we  produce  azoxy-,  azo-,  and  hydrazo-com pounds  (see  Azo  Com- 
pounds) . 

Benzenesulphonic  acid,  C^HsCSOgH),  is  obtained  by  heating  benzene 
with  concentrr.ted  H2SO4  and  forms  deliquescent  crystals. 

Benzenpdisulphonic  acid,  CfiH4(S03H)2,  is  produced  on  warming  ben- 
zene with  sulphuric  acid  anhydride,  and  oc3urs  in  two  isomeric  modifica- 
tions.    The  third  one  can  only  be  obtained  indirectly. 


OXY BENZENE  COMPOUNDS.  479 

2.  Oxybenzene  Compounds. 

a.  Phenol,  C6H5~OH,  and  its  Derivatives. 

Benzophenol,  phenol,  carbolic  acid,  phenylhydroxide,  CgHsCOH), 
occurs  to  a  slight  extent  in  urine,  in  castoreum,  among  the  putre- 
factive products  of  the  proteids,  and  forms  the  chief  constituent  of 
the  coal-tar  distilUng  between  170-230°.  This  product,  which  con- 
tains 30  per  cent.,  phenols  (p.  473),  is  shaken  with  caustic  alkaU,  and 
the  alkaline  solution  separated  from  the  impurities  floating  on  top 
and  treated  with  hydrochloric  acid.  The  phenols,  which  separate 
and  rise  to  the  surface,  are  removed  and  again  distilled,  and  the 
portion  distilUng  between  178-182°  consists  of  pure  phenol.  It  forms 
crystalline  masses,  having  a  characteristic  odor,  which  melt  at  40-42° 
and  which  often  tiu-n  red,  due  probably  to  impurities.  It  has  a  sharp 
burning  taste  and  causes  blisters  on  the  skin,  and  dissolves  in  15 
parts  water  and  with  great  readiness  in  alcohol  and  ether.  It  is 
poisonous  and  prevents  putrefaction,  hence  is  used  as  a  disinfecting 


Aqueous  solutions  of  phenol  turn  violet  with  ferric  salts,  and 
bromine-water  causes  from  very  dilute  solution  a  precipitate  of 
yellowish-white  tribromphenol,  C6H2B3(OH),  besides  C6H2Br3~OBr. 

Crude  carbolic  acid  contains  chiefly  cresols  (p.  491). 

Liquid  carbolic  acid  contains  about  10  per  cent,  water. 

Carbolic  water,  is  a  2  per  cent,  watery  solution  of  phenol. 

Bismuth  tribromphenolate,  (CjH2Br30)2=BiOH  + 31263,  is  used  in 
medicine  as  xeroform. 

Trinitro phenol,  picric  acid,  CeH2(N02)3~(OH).  Concentrated  nitric 
acid  converts  phenol  into  mono-,  di-,  or  trinitrophenol,  depending  upon 
the  length  of  action.  Trinitrophenol  is  also  obtained  as  an  end-product 
by  the  action  of  concentrated  nitric  acid  upon  many  other  aromatic 
bodies,  such  as  indigo,  aniline,  resins,  silk,  wool,  leather.  It  forms  yellow 
leaves  which  are  poisonous,  without  odor,  intensely  bitter  in  taste,  solu- 
ble in  water,  and  burning  without  explosion  when  ignited.  It  is  very 
sensitive  to  any  shock,  and  explodes  when  ignited  with  mercury  fulmi- 
nate. Pure  picric  acid  or  the  potassium  and  ammonium  compounds 
(picrate  powder),  or  mixed  with  carbon  and  saltpeter  or  guncotton,  etc., 
are  used  as  explosives  {melinite,  ly elite,  ecrasite.  etc.).  Picric  acid  colors 
silk  and  wool  beautifully  yellow  and  is  used  in  dyeing  and  in  microscopical 
technic.  Vegetable  fibers  (cotton)  are  not  colored.  It  behaves  just  like 
an  acid  and  forms  metallic  derivatives  which  form  well-defined  crystals 
and  readilv  explode:  C.HaCNOJoCONa)  and  alkyl  derivatives  such  as 
C,H2(N02);(OC2H,). 

Amide  phenols,  C5H4(NH2)(OH),  are  produced  in  the  reduction  of  the 


480  ORGANIC  CHEMISTRY, 

corresponding  nitro phenols.  The  p-compound  is  used  as  rodinal,  as  a 
developer  in  photography. 

Diamido  phenol,  Cetl3(NH2)2(OH),  is  also  used  for  the  same  purpose. 

Phenol  sulphonic  acids,  C6ri4(01i)(S03'H),  obtained  by  dissolving 
phenol  in  concentrated  sulphuric  acid,  forms  colorless  crystals. 

Zinc  phenolsulphonate,  (C6H40HS03)2Zn-l-7H20,  forms  colorless 
crystals. 

Sozoiodolic  acid,  C6H2l2(OH)(S03H)  +  3H20,  forms  prisms  which  are 
readily  soluble  in  water  and  alcohol,  which  like  the  corresponding  sodium 
salt  (C6H2l2(OH.)"S03*Na)  is  used  as  an  antiseptic. 

Phenylsulphuric  acid,  C6H5'0*S02*OH,  is  an  isomer  of  phenolsulphonic 
acid  and  is  unstable.  CgHsO'SOa'OK  is  found  in  the  urine  of  herbivora 
and  also  in  human  urine  after  partaking  phenol. 

Phenolmethyl  ether,  anisol,  C6H5'0~CH3,  is  obtained  from  anisic  acid 
by  splitting  off  COg  or  by  the  action  of  methyl  iodide  upon  potassium 
plienolate.     It  is  a  liquid  boihng  at  152°. 

Phenolethyl  ether,  phenctol,  CgHgOCgHg,  is  prepared  in  an  analogous 
manner.     It  is  a  liquid  boihng  at  172°. 

p-PhenetoI  carbamide,  dulcin,  HjN-CQ-NHCCeH^O  02115),  sucrol, 
is  a  substitute  for  sugar,  as  it  is  250  times  sweeter  than  cane-sugar; 
forms  white  needles  which  are  not  very  soluble. 

Phenyl  ether,  CeHg-O-CeHg,  is  produced  in  the  dry  distillation  of 
copper  benzoate,  forms  long,  colorless  needles. 

Thio phenol,  CeHg-SH,  is  produced  in  the  reduction  of  benzene- 
sulphonic  acid,  CeHg-SOsH,  and  of  benzenesulphochloride,  CeH5~S02Cl. 
It  IS  a  disagreeably  smelling  liquid,  boiling  at  173°. 

b.  Dihydric  Phenols,  C6H4(OH)2,  and  their  Derivatives. 

The  three  possible  dioxybenzenes,  namely,  pyrocatechin,  resorcin,  And 
hydroquinone,  are  produced  from  the  corresponding  phenolsulphonic  acids 
by  fusing  them  with  alkali  hydroxides  and  are  used  in  photography  as 
developers  (p.  241). 

Pyrocatechin,  o-dioxybenzene,  C6H4(OH)2,  occurs  among  the 
products  of  the  dry  distillation  of  catechu  extracts,  many  gum 
resins,  and  wood.  It  is  also  found  in  the  urine  and  feces  of 
herbivora,  where  it  is  produced  from  protocatechuic  acid  (p.  494), 
which  exists  extensively  in  the  plant  kingdom.  It  forms  colorless 
prisms  which  melt  at  104°  and  which  are  soluble  in  water,  alcohol,  ether, 
with  strong  reducing  action.  The  solution  turns  dark  green  with 
ferric  chloride  and  with  alkalies  it  undergoes  oxidation,  turning 
green,  then  brown  and  black. 

Guaiacol,  C6H4(OCH0(9H),  pyrocatechin  monomethyl  ether,  is  pro- 
duced in  the  dry  distillation  of  guaiac  and  wood  and  forms  colorless 
crystals  melting  at  32°,  and  which  are  not  very  soluble  in  water,  but 
readily  soluble  in  alcohol.  It  forms  creosote  (p.  493)  when  mixed  with  the 
homologous  creosols. 

The  benzoic  acid  ester,  benzosol,  the  carbonic  acid  ester  as  duotal,  the 


J 


OXY BENZENE  COMPOUNDS.  481 

salicylic  acid  ester,  guaiacolsalol,  the  valerianic    acid    ester,  geosot,  also 
potassium  guaiacolsulphonate,  thiocol,  are  used  in  medicine. 
Veratrol,  CgH^CO  0113)2,  occurs  in  the  seeds  of  the  sabadilla. 

Resorcin,  m-dioxybenzol,  C6H4(OH)2,  is  obtained  on  fusing 
asafoetida,  ammoniacum,  galbanum,  and  other  gum-resins  with 
caustic  alkali.  It  is  produced  in  large  quantities  by  fusing  potassium 
benzenedisulphonate  with  KOH: 

CeH^CSOaK)^^  2K0H  =  CeH,(0H)2+  2K2SO3. 

It  forms  colorless  sweet  crystals  which  have  a  reducing  action 
and  melt  at  110°  and  which  are  soluble  in  1  part  water,  and  in  alcohol, 
ether,  and  glycerine.  The  watery  solution  gives  a  deep-violet  color- 
ation with  ferric  chloride  and  a  brown  with  alkalies. 

On  fusion  with  phthalic  anhydride  it  dissolves  in  caustic  alkali  with 
a  green  fluorescence  (formation  of  fluorescein).  On  fusion  with  NaNOa 
it  yields  resorcin  blue  or  lacmoid,  C12H9O3N,  which  acts  like  the  litmus 
pigment  (p.  493). 

Trinitroresorcin,  styphnic  acid,  C6H(N02)3(OH)2,  is  obtained  by  the 
action  of  nitric  acid  upon  resorcin  as  well  as  upon  galbanum  and  other 
resins  and  forms  yellow  crystals. 

Hydroquinone,  p-dioxybenzol,  C6H4(OH)2,  occurs  in  the  glucoside 
arbutin  and  is  obtained  in  the  dry  distillation  of  quinic  acid  and  by 
the  action  of  sulphur  dioxide  upon  quinone,  C6H4O2: 

CeH  A+  SO2+  H,0  =  0^602+  H2SO4. 

It  forms  colorless  crystals  which  have  a  strong  reducing  power 

and  which  are  soluble  in  hot  water,  alcohol,  ether,  and  melt  at  169°. 

The    watery    solution    turn    temporary    blue    with    ferric    chloride 

and  become  dark  quickly  in  the  air,  especially  in  the  presence  of 

alkah,  due  to  the  absorption  of  oxygen.     It  is  converted  into  quinone, 

C6H4O2,  by  all  oxidizing  agents    (by  boiling  with  ferric   chloride). 

This  quinone  is  characterized  by  its  odor.     Monochlor-  and  mono- 

bromhvdroquinone,    adurol,    are    used    as    photographic   developers 

(p.  241). 

Oinnone,  C„H402,  is  produced  on  the  oxidation  of  aniline  (ordinary  prep- 
aration) as  well  as  many  p-diderivatives  of  benzene,  thus  of  hydroquinone, 
of  phenolsulphuric  acid,  etc.  It  forms  yellow  poisonous  prisms  having 
a  characteristic  odor  and  which  color  the  skin  brown.      It  is  a  double 

ketone,  OC<Qjj=pjQ>CO,  and  is  the  type  of  a  large  group  of  compounds 

called  quinones.  The  quinones  are  strong  oxidizing  agents  and  combine 
with  the  hydroquinones,  forming  quinhy drones,  which  are  strong  colors: 
C6H4O2  +  C6He02=  C,2HioO,. 


482  ORGANIC  CHEMISTRY, 

From  nitrous  acid  and  phenols  we  obtain  nitrosophenols  or  quinon- 
oxims  (p.  331),  CeH,0=(N-OH). 

The  quinonchlorimides,  CeH<0(NCl),  and  quinondichlorimides, 
CjH^CNCOa,  are  also  derived  from  the  quinones  by  replacing  =0  by  =NC1. 

The  aniline  residue,  "NH-'CgHg,  can  replace  hydrogen  in  many  quinones, 
producing  anilidoquinones;  e.g.,  CeH2(NH*CeHg)202,  or  the  aniline  residue, 
"N'CjHg,  can  replace  oxygen,  forming  quinonaniles;  e  g.,  CoH4(N'CflH5)2. 

Tetrachlorquinone,  chloranil,  Ce"Cl402,  is  obtained  from  quinone  and 
many  other  benzene  compounds  by  the  action  of  chlorine  and  forms 
yellow  crystalline  scales  which  are  soluble  in  water. 

c.  Trihydric  Phenols,  C6H3(OH)3,  and  their  Derivatives. 

All  three  possible  trioxybenzenes  are  known,  namely,  pyrogallol 
(HO  position  1:2: 3  =-2;),  phloroglucin  (HO  position  l:3:5  =  s), 
oxyhydroquinone  (HO  position  1:2:4  a,  p.  469). 

Pyrogallol,  pyrogaUic  acid,  CeH3(OH)3,  is  produced  on  heating 
gallic  acid:  C«H2(OH)3COOH=C6H3(OH)3+C02.  Its  dimethyl  ether 
occurs  in  beech-wood  tar.  It  forms  colorless  crystals  having  a  bitter 
taste,  melting  at  131°,  and  soluble  in  1.7  parts  water.  Its  alkaline 
solution  absorbs  oxygen  energetically,  turning  brown,  and  is  used 
in  determining  oxygen  in  gaseous  mixtures.  Pyrogallol  has  a  strong 
reducing  action  being  oxidized  into  acetic  and  oxahc  acids  (used 
as  a  developer  in  photography).  It  colors  the  skin  and  hair  brown 
and  the  aqueous  solution  turns  dark  blue  with  ferrous  salts  and  red 
with  ferric  salts. 

Phloroglucin,  C8H3(OH)3,  occurs  in  a  few  plants  and  is  obtained  from 
different  resins  by  fusing  them  with  KOH.  It  forms  sweet,  colorless 
crystals  with  2  mol.  HgO.  Its  watery  solution  becomes  deep  violet  with 
ferric  chloride  and  is  converted  into  phloroglucite,  C8H3(0H).Hj,  by 
nascent  hydrogen. 

Filicic  acid,  Ci^HuOg,  the  active  constituent  of  the  male- fern  used  as  a 
tape- worm  remedy,  and 

Cotoin,  CeH2(CeH5'C0)(0-CH3)(0H)2,  the  constituent  of  the  coto-bark, 
are  phloroglucm  derivatives, 

Oxyhydroquinone,  CeH,(0H)3,  is  produced  on  fusing  hydroquinone 
with  caustic  potash.  The  aqueous  solution  of  the  colorless  crystals  turn 
bluish-green  with  ferric  chloride. 

d.  Tetra  and  Polyhydric  Phenols  and  their  Derivatives. 

Tetraoxy benzenes,  C6H2(OH)4.  The  s-compound  is  known  free  and  the 
others  only  as  methyl  ethers.  One  hexahydro-derivative  is  called  hetite, 
C8H2(OH)4He,  and  is  found  in  beet-root  molasses. 

Pentaoxy benzene,  CeH(0H)5,  is  not  known,  but  its  hexahydro-deriva- 
tive (p.  463). 

Quercite,  C8HJ2O5  or  C8H(0H)b(H),.  is  the  sweetish  substance  found 
in  acorns. 


AMIDO  BENZENE  COMPOUNDS,  483 

He xaoxy benzene,  Ce(0H)8,  forms  grayish-white  crystals  which  turn 
violet  when  exposed  to  the  air.  Potassium  hexaoxybenzcne,  C8(OK)9,  is 
the  explosive  potassium  carbon  monoxide  produced  on  passing  CO  over 
heated  potassium  as  well  as  in  the  manufacture  of  potassium. 

Inositfc,  phassBomannite,  CbHijOo  or  C(OH.)8(H)6,  hexahydrohexoxy- 
benzene,  occurs  in  the  liver,  spleen,  kidneys,  lungs,  brain,  and  heart  muscle 
and  muscular  tissue  and  in  various  plants,  grape-juice,  and  wine,  and 
especially  in  unripe  beans,  from  which  it  can  be  obtained  by  extraction 
with  water  and  precipitation  with  alcohol.  It  forms  with  2  mol.  water 
colorless,  sweet,  crystals,  and  exist  as  a  dextrorotatory,  a  laevorotatory, 
and  an  inactive  modification. 

Methyl  inosite,  pinite,  carthartomannite,  C7Hi4De  or  C8(CH3)(OH)8(H5), 
is  obtained  from  the  resin  from  Pinus  lambertiana  and  from  the  senna 
leaves.     It  forms  colorless,  sweet  crystals. 

3.  Amido  Benzene  Compounds. 

The  amines  or  amido  derivatives  of  benzene  may  be  considered  as  pro- 
duced by  replacing  H  of  benzenj  by  amido  groups, 

C,H,(NH,)  CeH,(NH,),  CeH  (NH,), 

Amidobenzene  Diamidobenzene  Triamidobenzene 

(a  monamine).  (a  diamine).  (a  triamine). 

or  by  replacing  the  hydrogen  of  ammonia  by  phenyl,  C^Hc: 

(C,H.)NH,  (C,H,),NH  (C,H,)3N 

Phenylamine  Diphenylamine  Triphenylamine 

(primary  amine).  (secondary  amine).  (tertiary  amine). 

Correspondmg  amido  derivatives  are  obtainable  from  the  benzene 
derivatives. 

Properties.  The  monamines  are  colorless  liquids  or  crystalline  solids 
which  are  not  readily  soluble  in  water,  and  which  are  volatile  with  steam. 
The  polyamines  are  nearly  all  crystalline,  more  soluble  in  water  than  the 
monamines,  and  not  volatile  with  steam.  They  are  quite  similar  in  be- 
havior to  the  aliphatic  amines  and  form  analogous  compounds.  Quater- 
nary amines,  (C8H5)N(CH)3-OH,  are  known.  o-Phenylendiaraine  and  its 
homologues  yield  benzodiazole  (p.  468),  with  acids  and  the  elimination 
of  water,  and  benzodiazine  with  aldehydes;  thus, 

/NH2    COH  /N=CH 

c,h/        +1       =2HP+C,h/      T    . 

\NH,     COH  \N=CH 

Quinoxaline. 

They  unite  in  the  same  way  with  aldehyde  acids,  ketonic  acids,  diketones, 
when  these  contain  neighboring  CO  groups.  The  compounds  of  m-  and 
p-diamines  are  unstable.  With  nitrous  acid  the  primary  amines  yield 
diazo  compounds  (p.  465> .  the  secondary  amines  yield  nitrosamines  (p.  330), 
(C8H.0(CH3)=N-NO,  the  tertiary  amine?,  nitroso  compounds,  which  con- 
tain the  NO  groups  in  the  benzene  nucleus,  CjH4(NO)-N=(CH3)5.^ 

Preparation.  The  primary  monamines,  diamines,  and  triamines  are 
obtained  from  the  corresponding  nitro  compound  by  reduction,  especially 
in  acid  solution  (see  Azo  Compounds).  The  secondary  and  tertiary  mon- 
amijies,  which  contain  alkyls,  are  obtained  by  the  action  of  alkyl  iodides 
upon  primary  cyclic  amines:  C,H,-NH,+CH3l=CoH,-NH-CH,+HI. 


484  ORGANIC  CHEMISTRY, 

Secondary  and  tertiary  monamines  are  obtained  by  heating  the  primary 
cyclic  amines  with  their  salts: 

C6H,-NH2+CoH,-NH2(HCl)=  (CeH5)2NH +NH,C1. 

Aniline,  amidobenzene,  phenylamine,  C6H5~NH2,  is  produced  by 
the  dry  distillation  of  many  organic  bodies  such  as  coal  (occurrence 
in  coal-tar),  of  bones,  indigo  (from  Indigo f era  anil,  hence  the  name). 
It  is  chiefly  prepared  by  the  reduction  of  nitrobenzene  in  acid  solution 
(see  p.  483)  by  warming  with  iron  filings  and  hydrochloric  acid. 
The  reduction  may  also  be  brought  about  by  zinc  or  tin  and  hydro- 
chloric acid  or  with  ammonium  sulphide  when  the  HjS  acts  as  the 
reducing  substance: 

CeH6-N02+  SHjS  =  C6H6-NH,+  2H2O4-  3S. 

Aniline  is  a  colorless,  poisonous  hquid  having  a  peculiar  odor 
and  boihng  at  184°.  It  turns  brown  in  the  air  and  is  but  sUghtly 
soluble  in  water  but  readily  soluble  in  alcohol  and  ether.  It  can 
be  easily  detected  even  in  very  dilute  solution  by  the  temporary 
deep-violet  color  it  gives  with  chloride  of  lime  solution  as  well 
as  the  blue  coloration  with  potassium  dichromate  and  sulphuric 
acid.  Aniline  has  a  neutral  reaction,  but  combines  directly,  Uke  all 
amine  bases,  with  acids,  forming  well-defined  colorless  salts;  i.e., 
(C6H5'NH2)HN03,  (CeH8-NH2)2H2SO,.  The  anihne  is  set  free  from 
these  salts  by  alkalies. 

The  aniline  dyes  are  not  derived  from  aniline,  but  have  been 
called  so  because  aniline  is  used  in  the  preparation  of  certain  of 
them. 

If  aniline  is  heated  with  fuming  sulphuric  acid,  we  obtain  p-amido 
benzene  sulphonic  acid,  or  sulphanilic  acid:  C6H4(S03H)(NH2). 

If  the  hydrogen  of  the  NHj  group  in  aniline  is  replaced  by  alcohol 
radicals  we  obtain  the  anilines,  whose  preparation  and  behavior 
correspond  to  the  amines: 

CHa-N  <  ^  CcH  rN  <  ^j^^  CeH,-N  <  ^g». 

Aniline.  Methylaniline.  Dimethylaniline. 


Trimethylphenyl  am-  Diphenylamine.  Triphenylamine. 

moinum  hydroxide. 

If  the  hydrogen  of  the  NHj  group  of  aniline  is  replaced  by  acid 


AMIDO  BENZENE  COMPOUNDS.  485 

radicals  we  obtain  the  anilides  (see  below),  which  are  compounds 
similar  to  the  amides  and  which  are  prepared  in  the  same  manner. 

If  the  hydrogen  of  the  benzene  ring  of  aniUne  is  replaced  by  "OCHj 
the  anisidines  or  methoxyanilines  are  obtained,  while  if  "OCjHs  is 
replaced  we  obtain  phenetidines  or  ethoxyanilines  (anisol  and  phenetol, 
see  p.  480). 

Acetanilide,  antifibrine,  CeHs'NHCCHj'CO).     Just  as  ammonium 
acetate  decompose  on  heating  into  acetamide  and  water  so  aniline 
acetate  decomposes  into  acetanilide  and  water  on  heating: 
CeHs-NH^CCH/COOH)  =  CeHsNHCCHgCO)  +  H  A 

Aniline  acetate.  Acetanilide. 

It  forms  leaves  which  are  not  readily  soluble  in  water  but  easily 
soluble  in  chloroform,  alcohol,  and  ether,  melting  at  113°  and  boiUng 
at  295°. 

As  a  primary  amine  it  gives  the  isonitrile  reaction  (p.  391).  If  it  is 
boiled  with  HCl  for  a  short  time  and  then  treated  with  a  phenol  solution 
and  then  a  chloride  of  lime  solution  added  a  violet- blue  coloration  is 
obtained  which  on  saturation  with  NHg  becomes  blue  (indophenoi  reac- 
tion). 

p-Bromacetanilide,  antisepsin,  CeH4Br-NH(CH3CO), 

Methylacetanilide,  exalgin,  CoHg-N  (CHg)  (CHg'CO) , 

Formanilide,  phenylformamide,  CeHg-NHCH'CO), 

Gallic  acid  anilide,  gallanol,  C6H6-NH-CO-C6H2(OH)3, 

Metarsenic  acid  anilide,  atoxyl,  CcHj-NH-AsOj,  are  all  used  in  medi- 
cine. 

Carbanilide,  diphenyl  urea,  (CeH5)NH-CO-NH(C8H5),  is  produced  by 
replacing  2  H  atoms  by  =C0  in  2  mol.  aniline. 

p-Acetylphenetidine,  phenacetine,  acetphenetidine,  C8H4(OCjH5)-NH~ 
(CH3CO),  forms  a  white  crystalline  powder  without  odor  or  taste,  nearly 


insoluble  in  water  and  melting  at  135°.  It  is  obtained  by  boiling  p- 
,  amidophenetol,  CeH4(0"C2H6)~NH2,  with  acetic  acid,  when  water  is  split 
off.     On  shaking  with  HNO3  it  turns  yellow. 


p-Amidoacetylphenetidine,  CeH,(0  CjHJNHCOC-CHa'NHj),  phenocoll 
and  its  salicylate,  salocoll  are  used  in  medicine 

p-Lactylphenetidine,  CeH^COCgHJ-NHCCHgCHOHCO),  lactophenine, 
forms  colorless  crystals. 

m-Phenylendiamine,  C8H4(NH2)2,  is  used  in  the  detection  of  nitrous  acid 
(p.  157),  and  forms  colorless  crystals. 

Dipheny lamina,  HgCj-NH-CeHs,  forms  white  scales,  which  are  nearly 
insoluble  in  water  but  readily  soluble  in  alcohol  and  ether.  The  solution 
of  diphenylamine  in  sulphuric  acid  becomes  deep  blue  with  oxidizing 
agents  (p.  167).  The  following  dyes  may  be  considered  as  derivatives 
of  diphenylamine,  and  may  also  be  considered  as  derivatives  of  quinon- 
imide  (i.e.,  from  quinone,  C8H4O2,  in  which  both  O  atoms  are  replaced  by 
the  imido  group  NH). 

Indophenoi,  O-HiCj-N-CBHi-OH,  is  red  in  alcoholic  solution  and 

blue  in  alkalies.     In  regard  to  its  formation  from  acetanilide,  see  above. 


486  ORGANIC  CHEMISTRY. 

Indoaniline,  O-H^CrN-CBHrNCCHa)^,  phenol  blue, 
Indamine,  HN-H4CJ-N-C8H4-NH2,  phenylene  blue  and   its   deriva- 
tives are  unstable  colors  which  appear  as  intermediary  products  in  the 
preparation  of  saffranin  and  methylene  blue. 

*  "M- ri    TT    _/-\_^    TT 

/)-Diethoxylethenyldiphenylamidine,  holocain,  ^^3~^<]\m-Q'ii-()-(fii' 

forms  colorless  crystals  which  are  used  as  a  local  ansesthetic  mstead  of 
cocam. 

Acoin,  (H,C-C8H,)HN-C=N(CftH,OC2H,)-NH(C6H<;OCH3),  phene- 
tyldianisylguanidine,  is  also  used  as  a  substitute  for  cocain. 

4,  Hydrazine  Compounds. 

The  cyclic  hydrazines  are  very  similar  to  the  aliphatic  hydrazines  (p. 
331),  but  are  less  basic.  They  reduce,  like  these,  alkaline  copper  solutions, 
are  readily  oxidizable,  but  more  resistant  towards  reducing  agents.  They 
combine  directly  with  acids,  forming  salts,  and  also  with  aldehydes  and 
ketones,  with  the  elimmation  of  water  (p.  351.  11);  hence  they  form  with 
the  sugars  crystalime  compounds,  the  hydrazonrs  and  osazones  (p.  45'J). 

Mixed  hydrazines  are  also  known;  i.e.,  (CeHOlCaHjN-NHj.  Sym- 
metrical hydrazines,  i.e.,  (CeH5)HN-NH(CH3),  are  called  hydrazo  com- 
pounds. Hydrazides  correspond  to  the  amides.  They  are  obtained  by 
the  reduction  of  the  diazo  compounds  (p.  509)  or  from  the  neutral  solu- 
tions of  nitro  compounds  (p.  47^. 

Phenylhydrazine,  CeHg-HN-NHy,  serves  as  a  reagent  in  the  detection 
of  aldehydes,  ketones,  sugars,  and  melts  at  18°. 

Benzoyl    hydrazide,    (CeH5CO)HN-NH2,  serves  in   the  preparation 

of  hydrazoic  acid,  HN <^%     Nitrous  acid  converts  it  into  benzoylhy- 

drazoate    (benzazide),   (CoH5-CO)HN-NH2+HN03=(C8H6CO)N3+H20, 
which  on  boiling  with  caustic  alkaU  yields 

.N  /N 

CeH^-CO-Nai  +2NaOH=C6H5-COONa  +  NaN<'l|  -f  H-jO. 

Benzoylhydrazoate.  Sodium  benzoate.     Sodium  hydrazoate. 

From  this  last  substance  the  very  explosive  hydrazoic  acid,  N3H  (p. 
151),  is  set  free  by  treatment  with  sulphuric  acid. 

COMPOUNDS  WITH  SEVEN  CARBON  ATOMS  UNITED  TOGETHER. 
I.  Toluene  Compounds. 

Toluene,  methyl  benzene,  toluol,  C6H5~CH3f  is  produced  besides 
benzene,  etc.,  in  the  dry  distillation  of  certain  resins,  especially  Tolu 
balsam,  also  of  wood  and  coal.  It  is  obtained  from  coal-tar  (p.  473) 
by  fractional  distillation  as  a  liquid  similar  to  benzene  and  boiling  at 
110°. 

If  in  toluene  the  hydrogen  of  the  benzene  ring  is  substituted  we  ob- 
tain toluene  compounds  of  purely  benzene  character,  while  if  the  hydro- 
gen of  the  aliphatic  side-chain  be  substituted  we  obtain  compounds  of  a 


TOLUENE  COMPOUNDS.  487 

more  aliphatic  character.  By  substitution  in  the  benzene  ring  and 
in  the  side-chain  we  obtain  compounds  of  a  mixed  character.  Deriva- 
tives of  toluene  containing  the  radical  C<,H5~CH2~  are  called  benzyl, 
the  radical  CeHs'CO,  benzoyl,  the  radical  ~CeH4~CH3,  toluyl  or 
tolyl  compounds.  In  regard  to  the  further  nomenclature  of  the 
toluene  derivatives  see  p.  471. 

Chlortoluenes,  CbH4C1(CH.^);  all  three  isomers  are  known  as  well  as  the 
brom-  and  iodotoluenes  (Preparation,  p.  474). 

Nitrotoluencs,  C6H<(N()2)CH3;  all  three  isomers  are  known.  By  the 
action  of  concentrated  nitric  acid  upon  toluene  we  obtain  the  crystalline 
para-  and  the  liquid  orthonitrotoluejie. 

Toluidines,  amidotoluenf  s,  C6H4(NH2)(CH3);  the  three  isomers  are 
formed  in  the  reduction  of  the  three  nitrotoluenes.  Ortho-  and  meta- 
toluidine  are  fluids  and  paratoluidine  a  solid. 

Benzyl  chloride,  CeHg-CHX/l,  as  well  as  the  bromide  and  iodide,  form 
colorless  liquids  with  a  pungent  odor  (Preparation,  p.  474). 

Benzal  chloride,  CoH^-CHClg.  and  benzotrichloride,  CeHfi-CCl,,  are 
formed  on  the  further  action  of  chlorine  upon  boiling  toluene. 

Benzylamine,  CeH^-CHgNHg,  is  produced  by  heating  benzyl  chloride 
with  ammonia  and  consists  of  a  colorless  liquid  with  a  strong  alkaline 
reaction. 

Benzylcyanide,  CgHg-CHaCN',  forms  the  ethereal  oil  of  the  nasturtium 
and  garden  cresses  (Lepidium  sativum)  accompanied  by 

Benzylisosulphocyanide,  benzyl  mustard-oil,  CeHg-CH^-NCS. 

Benzylalcohol,  C6H5~CH20H,  occurs  as  the  cinnamic  and  benzoic 
acid  benzyl  ester  in  storax,  balsam  of  Peru,  and  Tolu  and  is  prepared 
from  benzaldehyde  by  the  action  of  alkali  hydroxides  or  nascent 
hydrogen  or  by  heating  benzylacetate  with  caustic  alkahes  (p.  344,  3). 
It  is  a  colorless  thick  liquid,  boiling  at  207°: 

CeH5'CH3Cl+  C,U,0,K  =  CoH.rCH2(C,H302)  +  KCl; 

Benzylchlorid.     Pot.  acetate.  Benzylacetate. 

CJlrClUG.Ti.O,)  +  KOH  =  C.H5-CH,0H+  C^HgO^K. 

Benzylacetate.  Benzyl  alcohol. 

Benzylaldehyde,  oil  of  bitter  almond,  CeH5~CH0,  is  analogous  to 
the  aliphatic  aldehydes  and  is  obtained  by  distilUng  a  salt  of  benzoic 
acid  with  a  salt  of  formic  acid  (p.  351,  12),  also  by  heating  benzal- 
chloridewith  water:    CeHs-CHCl^+HOH  =CeH5-CHO+2HCl. 

Ordinarily  it  is  prepared  from  bitter  almonds  by  the  decom- 
position of  the  glycoside  amygdalin  contained  therein  (p.  384). 
Thus  obtained  it  is  generally  mixed  with  hydrocyanic  acid  as 
C6H5-CHO(CN)  (see  p.  351,  9)  and  forms  the  oil  of  bitter  almonds 
of  the  druggist.  Benzaldehyde  is  a  colorless  liquid,  boiling  at  180°, 
having  a  characteristic  odor,  and   giving   all  the   reactions    of  the 


488  ORGANIC  CHEMISTRY. 

aldehydes,  yielding  benzoic  acid  on  oxidation  and  benzyl  alcohol  by 
reduction  (sodium  amalgam). 

The  aromatic  aldehydes  are  prepared  in  an  analogous  manner 
to  the  aliphatic  aldehydes  or  by  the  action  of  CO+HCl  in  the  pres- 
ence of  AICI3  upon  the  cyclic  hydrocarbons  (Gattermann's  method). 

Cyclic  aldehydes  do  not,  like  the  aliphatic  aldehydes,  yield  aldehyde 
resins  when  treated  with  alkali  hydroxides,  but  yield  acids  and  primary 
alcohols;  i.e., 

2C8H5-CHO  +  KOH = CeHg-COOK  +  CeHg-CH^-OH. 

On  warming  aromatic  aldehydes  with  an  alcoholic  solution  of  potas- 
sium cyanide,  bodies  having  double  the  molecular  weight  of  the  aldehyde 
are  produced,  these  bodies  being  derivatives  of  dibenzyl,  HJ^-Hj^f 
CjHs-CHa;  thus  benzyl  aldehyde,  2C6H5-CHO  =  C6H5-CO-CH(OH)-C6H5, 
benzoin.  Anisaldehyde  similarly  yields  aniso'in,  cuminaldehyde,  cuminom, 
etc. 

On  oxidation  these  bodies  give  diketones;  thus  benzoin  yields  benzil, 
CgHg-CO^CO^CeHs,  cuminom,  yields  cuminil,  anisoin,  anisil,  etc.  These 
on  heating  with  caustic  alkalies  form  alcohol  acids;  thus,  {G^^^ 
C(OH)-COOH,  henzilic  acid,  etc. 

Benzoic  acid,  phenyl  formic  acid,  CeHs^COOH,  occurs  in  many 
resins,  especially  in  the  gum  benzoin,  also  in  balsam  of  Peru-and  Tolu, 
and  as  a  component  of  hippuric  acid  in  fresh  herbivorous  urine  and 
free  in  decomposed  urine  and  as  a  constituent  of  the  glucoside  populin 
in  the  silver  poplar. 

Benzoic  acid  is  produced  on  the  oxidation  of  all  hydrocarbons, 
alcohols,  aldehydes,  ketones,  ketonic  acids,  etc.,  which  are  derived 
from  benzene  by  replacing  one  H  atom  by  a  monovalent  side-chain. 
Thus  CeHs-CHg,  C6H5-C2H5,  C6H5-C3H7,  etc.,  all  yield  CeHs-COOH 
on  oxidation  (p.  473).  It  may  be  obtained  synthetically  from  mono- 
brombenzene,  sodium,  and  carbon  dioxide, 

CeH5Br4-  2Na+  CO2  =  CeHs-COONa-t-  NaBr, 

and  the  sodium  benzoate  decomposed  by  HCl. 

It  is  also  obtained  from  benzaldehyde  (which  see)  by  the  action 
of  alkali  hydroxides.  It  is  ordinarily  prepared  by  heating  gum 
benzoin  when  the  benzoic  acid  sublimes  or  by  boiling  hippuric  acid 
(p.  490)  with  hydrochloric  acid  whereby  the  hippuric  acid  decom- 
poses into  glycocoll  and  benzoic  acid  (Benzoic  acid  from  urine)  or 
by  heating  benzotrichloride  with  water: 

CeH5-CCl3+ 2H0H  =  CeH5^C00H+  3HC1. 


TOLUENE  COMPOUNDS.  489 

Benzoic  acid  forms  large,  shining  crystals  which  have  a  faint 
aromatic  odor  and  which  are  readily  sublimable.  These  crystals  melt 
at  121°  and  are  soluble  with  difficulty  in  cold  water,  but  more  readily 
in  hot  water  and  are  easily  soluble  in  alcohol  and  ether. 

The  salts  of  benzoic  acid  or  benroates  are  mostly  readily  soluble  in 
water.  Ferric  chloride  precipitates  neutral  benzoate  solutions  forming 
reddish-yellow  ferric  benzoate,  (CeH5-COO)3Fe,  which  is  soluble  in  fatty 
oils. 

Paramido benzoic  acid,  C6H4(NH2)(COOH).  Its  ethyl  ester  is  called 
ancesthesin  and  is  used  as  a  local  anaesthetic. 

Benzamide,  CeHg-CQ-NHa,  corresponds  to  acetamide  and  by  splitting 
off  HgO  is  converted  into 

Benzonitrile,  CgHg-CN,  a  liquid  having  an  odor  similar  to  oil  of  bitter 
almond.     The  cyclic  nitriles  behave  like  the  aliphatic  nitriles  (p.  330). 

Orthoamido benzoic  acid,  CeH4(NH2)(COOH),  anthranilic  acid,  is  pro- 
duced on  the  oxidation  of  indigo  and  is  prepared  from  phthalimide  (p.  497), 
and  serves  in  the  synthesis  of  indigo.  Its  methyl  ester  is  a  constituent  of 
the  ethereal  oil  of  orange  flowers,  pomegranate,  and  jasmin  flowers,  and 
is  used  in  the  preparation  of  perfumes. 

COO  FT 
Orthosulphaminbenzoic  acid,  CeH4<gQ  _attt  ,  when  heated  yields 

Orthosulphaminbenzoic  acid  anhydride,  orthobenzoic  acid  sulphimide, 

CO 
saccharin,  sycose,  CoRiKciQ  >NH,  forms  white  crystals  which  are  diffi- 
cultly soluble  in  water  but  readily  soluble   in  alcohol  and   ether,   and 
which  are  500  times   sweeter  than    cane-sugar,   and,  hence   used   as   a 
sweetening  agent. 

The  corresponding  m-  and  p-compounds  do  not  taste  sweet.  The 
sodium  compound  is  the  "readily  soluble  saccharin"  and  contains  water 
of  crystallization  and  is  called  crytallose,  saccharose. 

Benzyl  benzoate,  CeH5-COO(C6H5CH2),  is  used  in  medicine  under  the 
name  peruscabin,  and  its  solution  in  oil  is  called  peruol. 

Benzoylperoxide,  CcHs-CO-OO'OCCeH,,  and 

Benzoperacid,  CeHg'CO'OOH,  are  to  be  considered  as  H2O2,  in  which 
the  H  atoms  have  been  replaced  by  benzoyl.  *  The  first  melts  at  110°  and 
the  other  at  42°. 

Benzoyl  chloride,  CeHg-COCl,  is  obtained  from  PCI3  and  benzoic  acid 
as  a  fuming,  colorless  Uquid  which  is  used  in  introducing  the  benzoyl 
group  into  other  compounds: 

CeHs-OH  +  CeHs-COCl^CeHs-OOC-CeHg  +  HCl; 
CeH5-NH2+CflH,COCl  ^CeH.-NH-CO-CeHg  f  HCl. 

This  takes  place  readily  in  the  presence  of  caustic  alkalies  (Schotten-Bau- 
mann  reaction)  and  serves  in  detecting  -NH2,  -OH,  and  -NH  in  aromatic 
and  afiphatic  compounds.  ,^  xt  n  /xttt  r^  ti  r^r^s 

Omithuric  acid,  C,oH2oN204,  is  benzoylornithm,  (C4H7)(JNli'L6ll5.^0)2-- 
COOH,  occurs  in  bird  urine,  especially  on  feeding  with  benzoic  acid  and 


490  ORGANIC  CHEMISTRY, 

decomposes  on  heating  with  mineral  acids  into  omithin  (p.  375)  and 
benzoic  acid. 

Hippuric  acid»  C9H9N3O;  is  benzoyl  glycocoU: 

(COOH-CHp-NH^;  (C00H.CH2)NH-(CeHrC0-). 

GlycocoU.  Hippuric  acid. 

It  is  abundantly  found  in  urine  of  herbivora  and  in  small  amounts 
in  the  urine  of  carnivora.  In  the  passage  of  benzoic  acid,  toluene,  cinna- 
mic  acid  and  other  aromatic  bodies,  which  on  oxidation  yield  benzoic 
acid,  through  the  animal  organism  they  are  transformed  into  hippuric 
acid  and  are  eliminated  as  such  by  the  urine.  On  exclusive  vegetable 
diet  the  quantity  of  hippuric  acid  in  the  urine  of  carnivora  and 
herbivora  is  the  same.  Hippuric  acid  is  artificially  obtained  by 
heating: 

(C,H5-CO)NH2+CH2Cl-COOH  =  (CeH5-CO)-NH-(CH2'COOH)  +  Ha 

Benzamide.  Monchloracetic  acid. 

It  is  prepared  on  a  large  scale  from  fresh  urine  of  herbivora  by 
evaporating  it  to  a  sirup  and  after  cooling  (p.  488)  treating  with 
hydrochloric  acid.  The  hippuric  acid  which  separates  out  is  purified 
by  recrystallization.  Hippuric  acid  forms  colorless  columns  which 
are  not  soluble  in  cold  water  but  slightly  soluble  in  hot  water,  and 
very  soluble  in  alcohol  but  insoluble  in  petroleum  ether  (differing 
from  benzoic  acid).  On  boihng  with  acids  or  alkahes  it  decomposes 
into  glycocoU  arid  benzoic  acid: 

CHrNH(CeH6-C0)  CH^'CNH,)     C0H5 

I  +H,0=    I  +  I 

COOH  COOH  COOH 

The  same  decomposition  can  be  brought  about  by  micrococcus 
urese  in  the  alkaline  fermentation  of  urine,  hence  only  benzoic  acid  is 
found  in  putrid  horse  urine. 

Of  the  salts  of  hippuric  acid  the  yellow  ferric  hippurate  is  characterized 

by  its  insolub  lity.  ,  .        .       ,  .       ,  •  -..      ^  ,1 

Many  cyclic  acids  combine  m  the  animal  organism  with  glycocoU, 
RTilittine  off  HpO,  and  these  compounds  are  eliminated  by  the  urine; 
tEus  salicyUc  acid  as  salicyluric  acid,  (HOOC-CH,)-NH(CeH,-OH.CO); 
tolulic  acid  as  tohiHc  acid,  (H00CCH,)-NH(C«H,-CH3-C0),  cymene 
as  cuminuric  acid,  (HOOC-CHJ-NHCCeH^-C^H/CO),  etc.  Fhenaceturic 
acid,  (HOOC-CH,)-NH(CfiH,-CHoCO),  occurs  as  a  regular  constituent 
of  the  urine  of  herbivora.  These  compounds  must  not  be  mistaken 
for  the  urea  derivatives  (p.  414),  which  have  a  similar  termination. 


OXYTOLUENE  COMPOUNDS.  491 

2.  Oxytoluene  Compounds. 

a.  Monohydric  Phenols ,  C8H4(OH)(CH3),  and  their  Derivatives. 

.  All  three  possible  oxytoluenes,  the  cresols,  are  known.  The  three 
alcohol  phenols,  C8H4(OH)(CH20H),  related  thereto  are  called  saligenin, 
m-  and  p-oxybenzyl  alcohol,  and  yield  on  oxidation  three  acids, 
C8H4(OH)(COOH),  salicylic  acid,  p-  and  m-oxybenzoic  acids. 

Cresols,  methyl  phenols,  C8H4(0H)  (CH3) .  All  three  isomers  occur 
with  phenol  in  the  heavy  coal-tar  oil  and  wood-tar  oil  and  form  as 
alkali  cresol-sulphates  the  chief  portion  of  the  phenols  of  the  urine 
of  carnivora  and  herbivora.  The  cresols  form  colorless  prisms  having 
an  odor  similar  to  phenol  and  are  difficultly  soluble  in  water. 

A  fluid  mixture  of  the  three  cresols  (pure  tricresol,  enterot)  contain* 
ing  10-15  per  cent,  hydrocarbons  is  called  crude  carbolic  acid  and 
forms  the  portion  of  the  coal-tar  which  distils  over  between  187* 
and  210°. 

The  addition  of  soaps  increases  the  solubility  of  the  cresols,  hence 
such  mixtures  are  used  as  more  or  less  poisonous  disinfectant  agents  under 
the  namefcf  lysol  (containing  50  per  cent,  cresols),  bacillol,  desinfectol, 
creolin,  cresolin,  lysiiol,  phenolin,  sapocarhol,  saprol.  In  solveol  the  sol- 
ubility of  the  cresols  in  water  is  increased  by  sodium  cresotate  and  in 
solutol  by  sodium  cresol.     Cresylic  acid  is  m-cresol 

Dinitro-orthocresol  potassium,  C8H2(N02)2(CPi3)(OK),  as  antinonnin 
is  used  to  kill  caterpillars  and  worms. 

Europhen,  (HO)(CH3)(C,H«)CeHrC6H2(C4Ho)(CH3)(0-I),  diisobutyl 
orthocresol  monoiodide,  is  a  yellow  amorphous  powder  insoluble  in  water. 

Methylamidocresol,  C6H^(NH-CH3)(CH3)(OH),  amidol,  serves  as  a 
developer;  its  salts  are  also  called  metal. 

Saligenin,  o-oxybenzyl  alcohol,  C6H4(OH)(CH2'OH)  is  obtained 
by  the  decomposition  of  the  glucoside  salicin  (which  see)  occurring 
in  the  bark  of  the  willow-tree  by  the  action  of  dilute  acids.  It 
forms  shining  leaves  which  are  soluble  in  hot  water,  alcohol,  and 
ether  and  its  aqueous  solution  turning  deep  blue  with  ferric  chloride. 

m-Amido-o-oxybenzyl  alcohol,  edinol,  is  used  as  a  photographic  devel- 
oper. 

Salicyl  aldehyde,  CeH4(0H)  (CHO),  occurs  in  the  volatile  oil  of  the 
varieties  of  Spiraea  and  is  produced  by  the  oxidation  of  saligenin.  It 
forms  a  liquid  which  is  not  readily  soluble  in  water  and  this  solution 
turns  deep  violet  with  FejClj. 


492  ORGANIC  CHEMISTRY. 

All  aromatic  oxyaldehydes  may  also  be  prepared  by  the  action  of 
chloroform  and  caustic  alkali  upon  the  phenols  (Reimer's  synthesis) : 

CoH5-OH+CHCl3+3KOH  =  CeH,(OH)(CHO)+3KCl  +  2HaO. 

Salicylic  acid,  CoH4(OH)~COOH,  o-oxybenzoic  acid,  a  phenol 
acid,  occurs  free,  besides  salicyl  aldehyde,  in  various  varieties  of 
Spirsea,  and  as  its  methyl  ester  in  oil  of  wintergreen  (p.  349).  It  is 
obtained  by  the  oxidation  of  saligenin  or  salicyl  aldehyde  and  on  a 
large  scale  by  allowing  sodium  to  act  upon  phenol  and  saturating  the 
sodium  phenolate  obtained  with  COj  in  the  cold  and  under  pressure 
and  then  heating  the  sodium  phenol  carbonate,  CcH5~0~C00Na,  to 
130°  when  it  is  converted  into  sodium  salicylate  (Kolbe's  synthesis 
of  cyclic  oxy acids).  The  sodium  salicylate  thus  obtained  is  decom- 
posed by  an  inorganic  acid. 

Salicylic  acids  form  colorless  needles  or  a  crystalline  powder 
which  is  not  readily  soluble  in  cold  water  (in  500  parts)  but  readily 
soluble  in  alcohol  and  ether.  The  solutions  of  the  acid  as  well  as  of 
its  salts,  the  salicylates,  turn  violet  with  ferric  chloride.  It  is  used  as  an 
antifermentive  agent,  and  is  non-poisonous,  and  as  it  is  a  phenol  it 
forms  three  series  of  esters,  thus : 

^6H4<coOCH3  ^»^*<COOH  ^'»^*<C006h,* 

Salicylic  acid  Methyl  Salicylic  acid 

methyl  ester.  salicylic  acid.  dimethyl  ester. 

Sodium  salicylate,  C6H4(OH)COONa,  forms  white  soluble  scales  hav- 
ing a  sweet-salty  taste. 

Lithium  salicylate,  C6H4(OH)COOLi  +  H20,  is  a  white  crystalline 
powder  soluble  in  water. 

Mercuric  salicylate,  C6H3(OH)COOHg,  has  a  different  structure  from 
the  other  salicylates  in  that  one  valence  of  the  mercury  atom  is  combined 
with  a  carbon.  It  forms  a  white  odorless,  tasteless  powder,  insoluble  in 
water  but  soluble  in  alkali  chlorides,  hydroxides,  and  carbonates. 

Basic  bismuth  salicylate,  C6H4(OH)COO-Bi(OH),,  forms  a  white 
crystalline  odorless  and  tasteless  powder  which  is  insoluble  in  water  and 
alcohol. 

Methyl  salicylate,  C6H4(OH)-COO(CH3),  forms  the  oil  of  wintergreen, 
and  is  used  in  medicine. 

Phenyl  salicylate,  salol,  C6H4(OH)-COO-CeH5,  is  prepared  by  heating 
sodium  salicylate  with  sodium  phenolate  in  the  presence  of  P0C1.<  or 
COCI2.  It  forms  a  white  crystalline  powder  which  is  nearly  insoluble  in 
alcohol,  ether,  and  chloroform,  melting  at  42°,  and  having  a  faint  aro- 
matic odor  and  taste. 

??-Amidophenylacetyl  salicylate,  salophene,  C8H4(OH)'COO-CaH^-NH 
(CHa~CO),  form  leaves  which  are  insoluble  in  water. 


OXYTOLUENE  COMPOUNDS,  493 

Acetyl  salicylic  acid,  CaH4(00C  CH3)-C00H,  aspirin,  forms  crystals 
readily  soluble  in  water. 

Dithiosalicylic  acid,  HOOC(HO)H3C,-S-S-CoH3(OH)-COOH.  The 
basic  bismuth  salt,  ihiojorm,  is  used  in  medicine. 

Methylamidooxybenzoate,  C6H3(NH2)(OH)(COOCH3).     The  p-amido- ' 
m-oxy-compound  is  called  orthoform,  the  m  amido-jo-oxy-compound,  new 
orthoform,  the  p-amido-o-oxy-compound  combined  with  dimethylglycocoll, 
nervanin;  all  are  used  in  medicine. 

Anisyl  alcohol,  o-methyloxybenzyl  alcohol,  CeH4(OCH3)(CH20H),  is 
produced  from  its  aldehyde  by  reduction  (by  caustic  alkali,  see  Benzal- 
dehyde)  and  forms  crystals  melting  at  45° 

Anisic  aldehyde,  C8H4(OCH3)(CHO),  is  prepared  by  the  oxidation  of 
anethol  (which  see)  and  is  the  odoriferous  principle  of  the  hawthorn  and 
forms  a  liquid  which  boils  at  248°. 

Anisic  acid,  Cr.H4(OCH3)(COOH).  produced  by  the  oxidation  of  anisic 
aldehyde  or  anethol,  forms  crystals  which  melt  at  185°. 

h.  Dihydric  Phenols,  C6H3(OH)2(CH3),  and  their  Derivatives. 

All  six  of  the  possible  dioxytoluenes  are  known,  but  only  orcin  and 
homopyrocatechin  will  be  treated  of.  The  alcohol  phenols  or  dioxybenzyl 
alcohols,  C6H3(OH)2(CH20H),  related  to  these  are  not  known  free,  never- 
theless six  possible  dioxybenzyl  aldehydes  and  dioxybenzoic  acids  have 
been  prepared  synthetically. 

Orcin,  CeH3(OH)2(CH3),  exists  free  to  a  slight  extent  in  the  lichens  of 
the  varieties  Rocella,  Evernia,  and  Lecanora,  and  can  be  obtained  from  the 
ester,  erythrin  (p.  496),  contained  in  these  lichens.  Orcin  forms  colorless 
sweet  crystals  whose  watery  solution  turns  bluish  violet  with  ferric  chlo- 
ride and  temporary  deep  violet  with  a  solution  of  chloride  of  lime. 

If  an  ammoniacal  orcin  solution  is  allowed  to  stand  in  the  air  it  absorbs 
oxygen  and  nitrogen  and  a  red  crystalhne  pigment,  orcein,  C2RH24N2O7, 
the  chief  constituent  of  the  orseille  pigments  (called  when  pure  persio,  cud- 
bear, red  indigo)  is  produced.  These  also  may  be  obtained  directly  by 
fermenting  the  above-mentioned  lichens  with  ammonia. 

If  an  ammoniacal  orcin  solution  is  allowed  to  stand  with  alkali  car- 
bonate, litmus  pigment,  which  becomes  red  with  acids  and  blue  again  with 
alkalies  is  obtained.     This  cons' sts  chiefly  of  azolitmin,  C7H7NO,. 

Homopyrocatechin,  C6H3(OH)2(CH3),  obtained  from  creosol  by  heating 
with  HI,  forms  hygroscopic  crystals. 

Creosol,  CfiH3(CH3)(OCH3)('OH),  methyl  homopyrocatechin,  is  a  liquid 
boiling  at  220°,  which  is  very  similar  to  guaiacol  (p.  480), and  forms,  when 
mixed  with  this, 

Creosote,  which  is  obtained  from  beech-wood  tar  by  fractional  dis- 
tillation between  200°  and  220°.  It  forms  a  yellowish  liquid  having  a 
penetrating  smokv  odor.  Its  alcoholic  solution  turns  deep  blue  with  a 
small  quantity  of  ferric  chloride  solution  and  dark  green  witii  a  larger 
quantity.  Creosotal  is  the  name  given  to  a  mixture  of  guaiacol  and 
creosol  carbonates. 

Protocatechuic  alcohol,  C6H,(OH)2(CH20H),  is  unknown. 
Protocatechuic    aldehyde,   (^6H,(OH)2-CHO,    obtained   from   vanilhn 
(pi  494)    or   from   pyrocatechin   by  means   of   the    chloroform   reaction 
(p.  492).     It  forms  colorless  crystals  which  are  soluble  1r  water,  and 
whose  aqueous  solution  turns  deep  green  with  ferric  chloride. 


494  ORGANIC  CHEMISTRY. 

Vanillin,  methyl  protocatechuic  aldehyde,  CH3(0-CH3)(OH)(CHO), 
the  odoriferous  constituent  of  the  vanilla  bean.  It  is  obtained  by 
extracting  the  vanilla  bean  with  ether.  It  is  also  found  in  the  Siam 
benzoin  and  in  certain  other  resins,  in  the  sugar-beet,  asparagus,  etc.,  to 
a  slight  extent. 

It  is  artificially  prepared  from  coniferyl  alcohol,  contained  in  the 
glucoside  coniferin  (which  see),  by  oxidation; 

/OCH-  /OCHj 

CflHaf-OH        +60-=C,H3fOH     +2CO2+2HOH. 
XCaH.OH  \CHO 

Coniferyl  alcohol.  Vanillin. 

It  is  also  produced  from  guaiacol  and  chJoroform  (p.  492) : 

CeH,  <§™'  +  CHCI3 + 3K0H = CgH^COH)  <  ^g^^ + 3KCI  +  2H2O. 

It  is  prepared  on  a  conjmercial  scale  by  the  oxidation  of  isoeugenol, 
CeH3(0-CH3)(OH)(CH  :  CH-CHa)  (see  Eugenol,  p.  499). 

Vanillin  crystallizes  in  long  characteristically  smelling  needles,  which 
are  soluble  in  water,  alcohol,  and  ether,  and  which,  when  heated  with 
HCl,  decompose  into  methyl  chloride  and  protocatechuic  aldehyde: 

CeH3(OH)<ggH3  +  HCl=C,H3^^^^)^  +  CH3Cl. 

Piperonal,   C8ll3(CHO)<Q>CH2,    methylenprotocatechuic   aldehyde, 

forms  the  perfume  heliotropin,  used  to  be  prepared  by  the  oxidation  of 
piperic  acid  (p.  5J1),  but  now  from  safrol  (p.  500). 

Protocatechuic  acid,  pyrocateehin  carbonic  acid,  C8H3(OH)2~COOH, 
one  of  the  six  known  oxysalicylic  or  dioxybenzoic  acids,  is  obtained  by 
fusing  gum  catechu,  kino,  bentz^in,  asafoetida,  myrrh,  etc.,  with  caustic 
alkalies,  also  by  the  oxidation  of  its  aldehydes.  It  forms  colorless  needles 
which  are  soluble  in  water,  alcohol,  and  ether,  and  whose  solution  turns 
green  with  ferric  chloride. 

Hydroquinone  carbonic  acid,  ^entisic  acid,  CeH3(OH)2-COOH,  is  also 
one  of  the  six  oxysalicylic  acids  (p.  493). 

Veratric  acid,  C8H3(OCH3)2-GOOH,  pyrocatechuic  acid  dimethyl  ester, 
occurs  in  the  seed  of  the  sabilla  and  forms  colorless  crystals. 

c.  Trihydric  Phenols,  C8H2(OH)3CH3,  and  their  Derivatives. 

The  six  possible  trioxytoluenes  and  their  respective  alcohols,  aldehydes, 
and  acids  are  not  all  known. 

Methylpyrogallol,  CeH2(OH)3(CH3),  is  obtained  synthetically.  It« 
dimethyl  ether  occurs  in  beech-wood  tar. 

Trio xy benzyl  alcohol,  C«H2(OH),(CH2-OH),  gallic  alcohol,  and 

Trioxybenzaldehyde,  CeH2(OH)3(CHO),  are  also  obtained  synthetically. 

Gallic  Acid,  CyHeOs+HjO,  one  of  the  three  known  trioxybenzoic 
acids,  C6H2(OH)3(COOH),  occurs  free  with  tannin  in  the  oak-gall, 
pods  of  the  Divi-Divi,  in  tea  and  the  rind  of  the  pomegranate  root  and 


OXYTOLUENE  COMPOUNDS.  495 

many  plants.  It  is  also  found  combined,  and  indeed  generally  as  a 
glucoside,  in  certain  tannic  acids.  It  is  obtained  from  tannin  by 
boiling  with  dilute  acids  (see  below)  or  by  fusing  bromprotocatechuic 
acid  with  caustic  alkali: 

CeH,Br^  ^^^^j^  +  KOH  =  CK.iOB.)  <  ^^^)^+ KBr. 

Gallic  acid  consists  of  white  fine  needles  which  are  soluble  in  hot 
water,  alcohol,  and  ether,  and  has  a  strong  reducing  action.  Its 
alkaline  solution  absorbs  oxygen,  and  turns  brown. 

Ferric  chloride  produced  in  a  watery  solution  of  gallic  acid  a  dark-blu 
precipitate,  gelatine  solution  gives  no  precipitate,  while  potassium  cyanide 
gives  a  red  coloration  (aiffering  from  tannin).  On  healing  gallic  acid  it 
decomposes  into  COg  and  pyrogallcl  (p.  482),  CeH3(OH)3,  and  on  oxida- 
tion it  yields  ellagic  acid,  (JjilieUy  (p.  ^96),  which  is  used  in  medicine 
under  the  name  gallogen. 

Basic  bismuth  gallate-iodide,  airojorm,  airogen,  airol,  C5H2(OH)3— 
COO-Bi(OH)I,  and 

Ba:ic  bismuth  gallate,  dermatoJ,  C6H2(OH)3COO-Bi(OH)2,  are  yellow 
amorphous  powders  without  odor  and  taste  and  insoluble  in  water,  alco- 
hol, and  ether. 

Digallic  acid,  ordinary  tannic  acid,  tannin,  C14H10O9+2H2O, 
an  anhydride  of  gallic  acid  (structure  below)  is  found  in  oak-galls, 
in  the  sumach,  and  in  red  wine.  It  is  obtained  from  gallic*  acid  by 
dehydrating  agents  and  can  be  recomposed  into  gallic  acid  by  boiling 
with  dilute  acids  and  alkalies: 

CeH2(OH)3-COO-C6H2(OH)rCOOH+HOH=2CeH2(OH),-COOH. 

It  is  ordinarily  obtained  by  extracting  oak-galls  with  ether  con- 
taining alcohol  and  evaporating  the  same. 

Tannic  acid  consists  as  a  colorless,  amorphous,  neutral,  dextrorotatory 
powder,  which  is  readily  soluble  in  water,  alcohol,  glycerine,  but  not  in 
ether.  It  has  a  strong  reducing  action  and  when  dissolved  in  the  presence 
of  ferric  salts,  tannic  acid  gives  a  deep-blue  coloration.  When  heated  it 
decomposes,  yielding  pyrogallol.  For  further  properties,  see  the  tannic 
acids  (belowV 

Tannigen,  diacetyl  tannin,  C,4Hs(CH3'CO)209,  and 

Alutrinium  tannate-tartrate,  Al2(C,HPe)2(Cj4H909)2'  are  brown  pow- 
ders soluble  in  water.  ,  1  1         i,-  u 

Mercurous  tannate  forms  colorless,  tasteless,  insoluble  scales  which 
have  a  deep  green  color.  . 

Lead  tannate,  obtained  from  basic  lead  acetate  and  tannic  acid,  forms 
when  mixed  with  lard  an  ointment  used  in  pharmacy. 

Tannic  acids,  tanning  bodies,  tannins,  are  the  names  given  to  the 
bodies  widely  disseminated  in  the  vegetable  kingdom,  which  are  soluble  in 


496  ORGANIC  CHEMISTRY, 

water,  have  an  astringent  taste,  give  black  or  green  precipitates  with 
iron  salts  (inks),  precipitate  proteids  and  gelatine  solutions,  and  form 
insoluble  compounds  with  animal  hides,  which  prevent  these  from 
putrefying  (leather  manufacture).  The  tanning  bodies  do  not  form 
one  group,  but  they  are  divided  into  tannogens  (cyclic  oxyacids), 
tannoids  (anhydrides,  oxidation,  and  condensation  products  of  the  tan- 
nogens), and  giucotannoids  (compounds  of  the  tannoids  with  the  sugars). 
According  to  their  origin  we  differentiate  between  ellagic,  coffee,  catechu, 
tormentULa,  kino,  quina,  moringa,  oak  (=tea),  quinova,  rheum,  fiiix,ratan- 
hia  tannic  acids  which  with  dilute  acids  form  colored,  resin-like  com- 
poimds  which  are  called  phlobaphenes. 

Quinic  acid,  hexahydrotetraoxybenzoic  acid,  CeH(0H)4(C00H)Hj, 
occurs  widely  distributed  in  the  plant  kingdom,  especially  in  the  cin- 
chona bark,  sugar-beets,  coffee-beans,  and  forms  active  prisms.  Its 
lithium  salt  is  called  urosin,  its  piperidin  salt  sidonal,  its  urea  salt  urol, 
its  anhydride  neusidonal,  which  are  all  used  in  medicine. 


COMPOUNDS  WITH  EIGHT  CARBON  ATOMS  UNITED  TOGETHER. 
I.  Dimethyl  Benzene  Compounds. 

Dimethyl  benzenes,  xylenes,  xylols,  C6H4(CH,)2.  From  coal-tar  by 
fractional  distillation  at  140°  we  obtain  a  colorless  liquid  which  consists 
of  a  mixture  of  the  three  isomeric  xylenes,  which  cannot  be  separated 
from  each  other  by  fractional  distillation,  and  hence  they  must  be  pre- 
pared synthetically  (p.  472).  On  oxidation  they  yield,  according  to  the 
energy  of  oxidation,  either  toluic  acids,  C6H4(CH3)-COOH,  or  phthalic 
acids,  CeH4(COOH)2.  In  regard  to  the  preparation  of  the  halogen  deriva- 
tives see  page  474. 

Oxy xylenes,  xylenols,  C6H3(OH)<™-S  have  all  the  properties  of  the 

phenols  and  occur  in  beech-wood  tar.  AH  six  isomers  are  known  and 
four  of  them  can  be  obtained  by  fusing  the  isomeric  xylene  sulphonic  acids 
with  caustic  alkali. 

Oxytoluic  acids,  cresotic  acids',  CeH3(0H)  <(.qqjj.  All  ten  possi- 
ble isomers  have  been  prepared. 

Oxy  phthalic  acids,  C6H3(OH)  <coOH-  ^^^  ^'"^  possible  isomers  have 
also  been  prepared. 

Dioxyxyhnes,  C,Ii,(01i),<^^';  five  are  known.  They  are  called  m- 
and  7)-xylorcin  (the  latter  also  /?-orcin),  o-,  m-,  and  p-xylohydroquinone 
(the  last  also  hydro phlorone). 

Dioxytoluic  acids,  C6H2(OH)2<^^^.  The  most  interesting  of  the 
known  Tsomers  is  orcin  carbonic  acid  or  orsellic  acid,  which  exists 
in  certain  lichens  as  diorsellic  acid  erythrite  ester  (Erythrin,  p.  493), 
S•'S4S^^^SS'^n^n>C4He(OH)2,   and   which   decomposes    on    boiling 


DIMETHYL  BENZENE  COMPOUNDS,  497 

with  Ba(0H)2  into  erythrite  and  orseilic  acid.    The  latter  splits  on  heat- 
ing into  orcin,  CflHalOH)/^!!^  and  COg. 

Numerous  other  acids  are  found  in  lichens,  so-called  lichen  acids,  and 
are  derived  from  orcin ;  still  the  mother  substance  of  these  acids  has  not 
been  investigated.  To  this  group  belong  cetraric  acid,  CaeHjoOja;  proto- 
cetraric  acid,  C3„H220i5,  contained  in  the  Iceland  moss,  and  yielding 
fumaric  and  cetraric  acids  on  cleavage;  evernic  acid,  C^yHjeOy;  lecanoric 
acid  (orseilic  acid),  0^,^11  ^JJj-,  lichsteric  acid,  CigHgoOg;  usninic  acid, 
CjsHiqO;;   parelhc  acid,  CajHieOg,  etc. 

r^OOTT 
Dioxyphthalic  acids,  C8H2'(OH)2<qqqjj;  six  are  known. 

CTT  OPT  * 

Meconinic  acid,  CeHaCO '0113)2  <(^Q^jj  ,  and 

Opianic  acid,  C,E.^{0-CB.,\<^^^^,  and 

Hemipinic  acid,  CoH2(OCH3)2<^^^g, 

are  produced  on  the  oxidation  of  the  plant-base  narcotine  (which  see); 

Tolyl  alcohols,  methylbenzyl  alcohols,  ^b^i<niJ^-Qxj') 

CTT 
Toluic  aldehydes,  methjdbenzyl  aldehydes,  C^B-iK^^^; 

CH 
Toluic  acids,  methylbenzoic   acids,   C6H4<^q^jt; 

PTT  OTT 
Toluylene  alcohols,  phthalyl  alcohols,  CgH^  <  qjj^qtt  ; 


Oxymethylbenzoic  acids,  ^bH*  <nQQ jj  i 


are  known  in  all  three  isomeric  forms,  namely,  o-,  m-,  and  79-compounds. 

Phthalic  acids,  benzendicarbonic  acids,  ^^i<nr)r\^i  are  produced  by 

the  oxidation  of  the  corresponding  three  xylenes,  as  well  as  all  isocyclic 
compounds  which  contain  two  alkyl  radicals  (p.  473). 

Ordinary  or  o-phthalic  acid  is  prepared  by  the  oxidation  of  naphthalene. 
From  this  it  follows  that  the  carboxyls  occupy  the  positions  1  :  2  (see 
Naphthalene). 

Phthalic  acid  forms  colorless  crystals  which  melt  at  213°,  and  are 
soluble  in  hot  water,  alcohol,  ether,  and  which  decompose  into  phthalic 

CO 
anhydride,  CeH4<^Q>0,  and  water  on  heating 

Iso-  or  m-phthalic  acid  forms  needles  which  melt  at  300°  and  sublime 
without  decomposition,  and  are  difficultly  soluble  in  hot  water. 

Tere-  or  p-phthalic  acid  is  obtained  by  the  oxidation  of  cymene,  tur- 
pentine, etc.  It  forms  an  amorphous  powder,  nearly  insoluble  in  water, 
alcohol,  or  ether,  and  sublimes  without  decomposing  and  without  melting. 

CO 
Phthalimide,  CeH^  <  qq  >  NH,  is  produced  by  passing  NH3  over  phthalic 

anhydride,  and  yields  anthranilic  acid  on  oxidation  (p.  489). 


498  ORGANIC  CHEMISTRY. 


2.  fithyl  Benzene  Compounds. 

Ethyl  benzene,  CeHsCCjH.,)  or  CoH^-CHj-CHg,  is  a  colorless  liquid  boil- 
ing at  134°,  and  is  only  obtained  synthetically. 

Phenyl  ethyl  alcohol,  CoHgCCgH^OH),  forms  the  chief  constituent  of 
the  odoriferous  principle  of  the  rose  and  hence  also  of  the  ethereal  oil  of 
roses. 

Methyl  phenylketone,  CeHg-CO-CHj,  acetophenone,  a  colorless  liquid 
having  a  peculiar  odor. 

All  aromatic  ketones  may  be  obtained  by  warming  an  aromatic  hydro- 
carbon with  an  acid  chloride  in  the  presence  of  AICI3  (Friedel-Craft's 
ketone  synthesis): 

CeHe  +  CH3-C0C1=  CflHs-CO-CHg  +  HCL 

If  a  benzoate  is  distilled  with  another  organic  salt,  then  mixed  ketones 
are  obtained: 

CeH^-COONa  +  CHa-COONa^Na^COa  +  CeHrCO-CH, 

Ethenyl  benzene,  styrene,  cinnamol,  C8H5~CH=CH2,  is  produced  by  the 
distillation  of  cinnamic  acid  with  hme,  when  CO2  is  evolved.  It  occurs  in 
the  storax  balsam  and  is  a  colorless  liquid  which  boils  at  146°  and  which 
undergoes  polymerization  readily. 

Phenylacetic  acid,  alphatoluic  acid,  CgHg-CHj^COOH,  the  only 
isomeric  toluic  acids  of  ethyl  benzene  known,  occurs  in  the  urine  and  in 
the  putrefactive  products  of  proteids.  ' 

Oxyphenylacetic  acid,  CeH4(OH)-CH2-COOH,  occurs  in  urine  and  is 
produced  in  the  putrefaction  of  tyrosin. 

Dioxyphenylacetic  acid,  C6H3(OH)2"~CH2~COOH,  homogentisic  acid 
(p.  494),  occurs  sometimes  in  the  urine,  which  causes  it  to  turn  dark  on 
standing. 

Oxyphenylamido  acetic  acid,  C6H,(OH)-CH(NH2)-COOH,  glycin,  is 
used  as  a  developer  in  photography. 

Mandelic  acid,  phenylglycoUio  acid,  CeHg-CHOH-COOH,  is  obtained 
from  benzaldehyde  and  HCN  +  HCl  (p.  405)  or  from  amygdalin  (see 
below).     The  Isevo  and  the  inactive  modifications  are  known. 

Mandelic  acid  nitrile  diglucose,  C6H5-CHO(Ci2H2iOio)~CN,  amygdalin, 
the  glucoside  of  the  bitter  almond,  etc.  (p.  384),  forms  colorless  crystals 
which  on  warming  with  dilute  acids  or  on  standing  with  water  by  the 
action  of  the  ferment  emulsin  contained  in  the  plants,  decomposes 
into  glucose,  hvdrocyanic  acid,  and  benzyaldehyde  (o  1  of  bitter  alm- 
onds): C2oH27NO„  +  2H20  +  2C6H,206  +  HCN  +  CeH5-CHO.  With  zymase 
it  decomposes  into  glucose  and  mandelic  acid  nitrile  glucose,  CgH^- 
CHO(C8H,,05)~CN,  which  is  only  further  split  by  emulsin  like  amygdalin. 
If  amygdalin  is  boiled  with  bases  a  development  of  NHg  takes  place  and 
amygdalic  acid,  CaoHgnOig,  is  produced,  which  on  heating  with  acids 
decomposes  into  glucose  and  mandelic  acid  (see  above). 


ALLYL  BENZENE  COMPOUNDS,  499 

COMPOUNDS  WITH  NINE  CARBON  ATOMS  UNITED  TOGETHER. 
I.  Trimethyl  Benzene  Compounds. 

The  three  trimethyl  benzenes,  CeH3(CH3)3,  mesitylene  (position  1,  3,  5), 
pseudocumene  (position  1,  2,  4),  and  hemellithene  (position  1,  2,  3), 
occur  in  coal  tar. 

Mesitylene,  C6H3(CH3)3,  is  obtained  when  acetone  is  heated  with 
sulphuric  acid;  hence  it  has  the  structure  (1,  3,  5)  (p.  470).  It  is  a 
liquid  having  a  peculiar  odor,  boiHng  at  163°,  and  which  yields  the 
following  three  acids  on  successive  oxidation: 

Mesitylenic  acid,  CeH3(CH3)2COOH,  isomer  of  the  xylic  acids. 

Uvitic  acid,  C6H3(CH3)(COOH)2,  isomer  of  methylphthaUc  acid. 

Trimesic  acid,  C5H3(COOH)3,  icomer  of  trimellitic  acid. 

Pseudocumene,  C6H3(CH3).,  a  liquid  boiling  at  169°  and  which  first 
yields  the  following  two  isomeric  acids: 

Xylic  acids,  C6H3(CH3)2COOH,  and  then  on  further  oxidation 

Methylphthalic  acid,  C6H3(CH3)(COOH)2,  and  its  isomer, 

Xylidic  acid,  C8H3(CH3)(COOH)2,  which  is  readily  oxidized  to 

Trimellitic  acid,  C6H3(COOH)3. 

Hemellithene,  CeH3(CH3)3,  a  liquid  boiling  at  175°  and  which  yields 
on  oxidation 

Hemellitic  acid,  CeH3(CH3)2COOH,  and  finally 

Hemillitic  acid,  CeH3(C00H).^,  an  isomer  of  the  benzene  tricarboxy 
acids  trimesic  and  trimellitic  acids. 

2.  Allyl  Benzene  Compounds. 

The  radical  C3H5  may  act  trivalent  as  glyceryl  and  monovalent 
as  allyl  (p.  437).  As  the  derivatives  of  the  allyls  of  the  fatty  series 
appear  as  unsaturated  compounds  and  pass  readily  over  into  the 
saturated  propyl  compounds,  so  also  the  aromatic  derivatives  of  the 
allyls  are  converted  into  the  saturated  propylbenzene  derivatives  by 
the  action  of  nascent  hydrogen. 

Allyl  benzene,  CgHs-CsHs  or  C8H5-CH=CH-CH3,  is  obtained  by  the 
action  of  bromallyl  upon  brombenzene  in  the  presence  of  sodium  (p.  472). 
It  is  a  pleasant-emelling  liquid. 

Anethol,  aniscamphor,  C8H^(0*CH3)(C3H5),  the  chief  constituent  of  oil 
of  anise,  fennel,  estragon,  crystallizes  on  cooling  these  oils  as  colorless 
scales  which  melt  at  21°,  and  boil  at  223°. 

Eugenol,  C6H3(OH)(0-CH3)(C3H5),  contained  in  the  ethereal  oil  of 
cloves  and  pimenta  (besides  C,nH,6  see  terpenes);  forms  an  aromatic- 
smelling  liquid  which  boils  at  252°,  and  which  forms  the  isomer  isoeugenol 
with  alcoholic  caustic  potash. 

Coniferylic  alcohol,  C8H3(OH)(OCH3)(C3H,OH),  occurring  in  the 
glucoside  coniferin,  melts  at  85°,  and  yields  vanillin  on  oxidation  (p  494). 

Asarone,  CcH2(OCH3)3C3H6,  contained  in  the  ethereal  oil  of  Asarum 


500  ORGANIC  CHEMISTRY. 

europseum,  Matiko,  and  Calamus,  forms  shining  crystals  which  melt  at 
61°. 

Apiol,  C6H(0-CH,)2(0-CH2-0)(CoH5),  contained  in  the  ethereal  oil 
of  the  parsley,  forms  shining  crystals  which  melt  at  32°. 

Safrol,  CeH3(0"CH2'0)(C3H5),  allylpyrocatechin  methylene  ether,  is  the 
chief  constituent  of  the  ethereal  oil  of  sassafras  and  of  the  camphor-oil 
obtained  in  the  preparation  of  camphor. 

Cubebin,  C6H3(0-CH20)(C3H^-OH),  occurs  in  cubebs. 

Cinnamyl  alcohol,  cinnamic  alcohol,  phenylallylalcohol, 
C6H5-C3H4(OH)  or  C6H5-CH=CH-,CH20H,  occurs  as  cinnamic  acid 
ester  in  storax  and  is  separated  therefrom  by  distillation  with  caustic 
alkali.  It  forms  needle-shaped  crystals  which  melt  at  33°,  have  an 
odor  similar  to  the  hyacinth,  and  are  not  very  soluble  in  water.  On 
oxidation  it  yields  cinnamic  aldehyde  and  cinnamic  acid. 

Cinnamic  aldehyde,  CeHs-CH^CH-CHO,  the  chief  constituent  of 
the  oijl  of  cinnamon  and  cassia,  forms  a  colorless  liquid  boiling  at  246°, 
is  insoluble  in  water,  and  has  an  odor  similar  to  cinnamon.  It  is  oxi- 
dized to  cinnamic  acid  even  in  the  air. 

Cinnamic  acid,  /?-phenylacrylic  acid,  C6H5~C3H302  or  C6H5~CH= 
CH~COOH,  occurs  in  certain  gum  benzoins,  in  storax,  Peru  and 
Tolu  balsam.  It  is  prepared  by  boiling  storax  with  caustic  alkali  and 
precipitating  the  alkali  cinnamate  by  HCl  or  by  boiling  benzalde- 
hyde  with  dry  sodium  acetate  and  acetic  anhydride,  which  abstracts 
water  (Perkin's  reaction,  which  may  be  made  to  undergo  numerous 
modifications) :  C6H5-CHO+  CH3  "COONa  =  C6H5-CH=CH-COONa-|- 
H2O;   or  from  benzal  chloride  and  sodium  acetate: 

C6H5-CHCI2+  CHj-COONa  =  C«H5-CH=CH-C00H+  NaCH-  HCl. 

Cinnamic  acid  forms  colorless  and  odorless  crystals  which  melt  at 
133°  and  which  are  difficultly  soluble  in  cold  water.  Ferric  chloride 
precipitates  yellow  ferric  cinnamate  from  its  solution.  On  oxidation 
it  yields  benzaldehyde  and  benzoic  acid  (p.  473). 

Sodium  cinnamate,  C6H5~CH"'CH~COONa,  is  used  in  medicine 
as  hetol.  Besides  the  ordinary  cinnamic  acid  three  modifications  of 
the  same  structure  are  known  which  are  readily  convertible  into 
ordinary  cinnamic  acid,  while  this  latter  cannot  be  transformed  into 
the  other  modifications.  These  are  called  allocinnamic  and  artificial 
isocinnamic  acid,  which  is  obtained  synthetically,  and  natural  iso- 
cinnamic  acid,  which  is  found  with  ordinary  and  allocinnamic  acid 
in  the  cleavage  acids  of  the  alkaloids  associated  with  cocaine. 


PROPYL  BENZENE  COMPOUNDS.  50l 

Besides  these  we  have  four  dicinnamic  acids  having  the  same 
structure,  namely,  the  diphenyltetramethylendicarboxyl  acids  or 
tuxillic  acids,  (C9H802)2,  which  are  also  cleavage  acids  of  the  alkaloids 
accompanying  cocaine. 

Atropic  acid,  a-phenylacrylicacid.CoHsOa  or  CH2=C(C6Hfi)-COOH,  the 
isomer  of  cinnamic  acid,  is  produced  on  the  cleavage  of  atropine  or  apo- 
atropineand  yields  two  diatropic  acids,  {0^1^02)2,  isomers  ot  the  truxillic 
acids  (see  above),  on  heating  with  water. 

Cinnamein,  CBH5'-CH=CH-COO(CeH5-CH2),  benzyl  cinnamate,  a 
constituent  of  storax,  balsam  of  Peru  and  Tolu,  forms  colorless  needles. 

Styracin,  C8H5-CH=CH-COO(CeH5-C3H4),  cinnamyl-cinnamate,  a 
constituent  of  storax  and  Peru  balsam,  forms  colorless  crystals- 

o-Oxycinnamic  acid,  coumaric  acid,  C6H4(OH)-CH=Cii-COOH  or 
C9H8O3,  occurs  in  Melilotus  officinalis,  forms  colorless  needles,  and  is  ob- 
tained from  coumarin  (see  below). 

Methoxyloxycinnamic  acids,  C6H3(OCH3)(OH)-CH=CH-COOH. 
Ferulic  acid,    contained  in   asafoctida,  and  the   isojerulic  acid  and  hes- 
peritic  acid,  cleavage  products  of  the  glucoside  hesperidin,  belong  to  this 
group. 

o-Oxycinnamic  anhydride,  coumarin,  C6H4<^q  jj  yCO  or  CeHeOy,  in 

sweet-scented  woodruff,  in  the  Tonka  bean,  in  clover,  sweet-scented  grass, 
as  well  as  in  other  plants.  It  forms  colorless  prisms  having  the  odor  of 
the  sweet-scented  woodrufif,  and  is  produced  by  heating  salicyl  aldehyde 
with  acetic  anhydride: 

C«H,(OH)CHO  +  (CH3-CO)20= CeH /^  H  J)^^  +  CH3-COOH  +  H^O. 

On  boiling  with  caustic  alkalies  coumarin  takes  up  HjO  and  is  converted 
into  coumaric  acid. 

Umbelliferone,  C9H6O3.  is  an  oxycoumarin,  occurs  in  the  spring  flax, 
and  is  formed  in  the  dry  distillation  of  many  umbelliferous  resins;  for 
example,  of  asafcetida,  galbanum,  etc. 

Daphnetin  and  ^sculetin,  CglieO^,  are  dioxycoumarins,  split  off  from 
the  glucosides  daphnin  and  sesculin. 

Dioxycinnamic  acids,  CgHgO,  or  CeH,(OH)2-CH=CH-C0OH.  CaJJeic 
add  is  obtained  as  yeliow  leaves  from  the  glucoside  coffee-tannin  occurring 
in  coffee.  Tlie  isomer  umbellic  acid  is  produced  from  umbelliferone  (see 
above)  by  abstracting  water. 

Closely  related  to  these  we  have  piperic  acid,  CigHjoO^  or 
CeH3(OCH3-0)-CH=CH-CH=CH-COOH,  a  cleavage  product  of  piperin 
(which  see). 

Dimethyltrioxycinnamic  acid,  sinapic  acid,  C^Ji^^^n  or 
Cj(CH3)2(OH)3-CH=CH-COOH,  is  a  cleavage  product  of  sinapin  (which 
see). 

3.  Propyl  Benzene  Compounds. 

The^  ally!  derivatives  are  readily  converted  into  the  propyl  benzene 
derivatives  by  means  of  nascent  hydrogen. 

Cumene,  cumol,  isopropyl  benzene,  CeH6~C3H7,  occurs  in  the  ethereal 
oil  of  the  Roman  caraway;  it  is  a  colorless  liquid  boiling  at  151°. 


502  ORGANIC  CHEMISTRY. 

Phenylpropyl  alcohol,  CfiHs-CjH^-CH^OH,  is  produced  by  the  action 
of  nascent  hydrogen  (sodium  amalgam)  upon  cnmamyl  alcohol. 

/5-Phenylpropionic  acid,  CeH.^-CjH^^COOH,  hydrocinnamic  acid,  is 
obtained  by  the  action  of  nascent  hydrogen  upon  cinnamic  acid.  It  is  a 
putrefactive  product  of  the  proteids. 

Tropic  acid,  CeH5-C2H3(OH)  "COOH,  a-phenyl-/?-oxypropionic  acid. 
This  inactive  acid,  which  can  be  converted  into  the  two  active  modifica- 
tions, is  obtained  on  the  cleavage  of  atropine  and  hyoscyanine. 

|S-Phenyl-a-amidopropionic  acid,  CeH5-C2H3(NH2)-COOH,  phenylala- 
oin,  is  a  cleavage  product  of  the  proteids. 

MeLlotic  acid,  C6H4(OH)-C2H^-COOH,  o  hydrocoumanc  acid,  one  of 
the  six  existing  oxyphenylpropionic  acids,  occurs  with  coumarm  in  clover. 
It  forms  needles  which  melt  at  38°. 

p-Hydrocoumaric  acid,  phloretic  acid,CfiH4(0H)-C,H^-C00H,  occurs 
in  urine  and  as  a  putrefactive  product  of  tyrosin. 

p-Oxyhydrocoumaric  acid,  C6H,(OH)-C2H3(OH)-COOH,  is  found  in 
the  urine  in  acute  atrophy  of  the  liver  and  in  phosphorus  poisoning. 

Tyrosin,  CeH4(OH)-C,H3(NH)rCOOH  or  C«H„N03,  amido- 
hydrocoumaric  acid,  p-oxyphenylamidopropionic  acid,  occurs  in 
cochineal,  in  dahlia  tubers,  and  in  the  animal  organism  under  patho- 
logical conditions,  nearly  always  accompanied  with  leucin.  It  is  a 
cleavage  product  of  the  horn  substances  and  the  proteids  (not  of  gel- 
atine) by  the  action  of  panceatic  juice,  by  boiling  with  acids  or 
fusing  with  alkali  hydroxides,  as  well  as  in  their  putrefaction,  and 
hence  is  also  found  in  old  cheese  {rvpSs).  It  can  also  be  prepared 
synthetically.  It  crystallizes  in  fine,  characteristically  grouped 
needles  which  are  laevorotatory,  soluble  with  difficulty  in  water  and 
insoluble  in  alcohol  and  ether,  and  melt  at  235°.  Dextrorotatory 
tyrosin  occurs  in  the  sugar-beet  sprouts. 

Orthonitrophenylpropiolic  acid,  CeH/N02)-C=C-C00H,  is  produced 
from  the  dibromide  of  o-nitrocinnamic  acid  by  alcoholic  caustic  alkali: 

C,H/N02)-CHBr-CHBr-C00H  +  2NaOH 

=  CeH,(N02)  -C=C-COOH  +  2NaBr  +  2H20. 

It  crystallizes  in  colorless  needles,  and  yields  indigo  blue  on  warming 
with  alkaline  reducing  agents. 

COMPOUNDS  WITH  TEN  OR  MORE  CARBON  ATOMS  COMBINED 

TOGETHER. 

Tetramethyl  benzenes,  C8H2(CH3)4.  These  are  called  durols,  iso- 
durols.  prehnitol,  and  are  prepared  synthetically. 

Benzene  tetracarbonic  acids,  CgHjCCOOH)^,  all  three  of  the  theoretically 
possible  ones  are  known  and  are  called  pyromellitic  acid,  prehnitic 
ucid,  and  mellophanic  acid. 


COMPOUNDS  WITH  TEN  OR  MORE  CARBON  ATOMS.  503 

p-Methylisopropyl  benzene,  cymene,  cymol,  C,oIIi4  or  CeH^(C3H7)(CH.^) 
(structure,  p.  519),  occurs  in  the  ethereal  oils  of  the  Roman  caraway  and 
thyme,  and  is  produced  by  heating  the  terpenes,  CjoHig,  with  iodine, 
and  the  camphors,  CjoHigO,  with  PgOg  (p.  520).  It  is  a  liquid  boiling 
at  175°,  which  on  oxidation  yields  p-toluhc  acid,  C6H4(CH3)(COOH) 
(p.  497),  and  then  terephthalic  acid,  CeH^CCOOH),  (pp.  497-4 V3). 

Cumyl  alcohol,  C6H,(C3H7)(CH20H),  and 

Cumic  aldehyde,  cuminol,  CeH^CC^H.^XCHO),  occur  in  Roman  caraway- 
oil  and  cicuta  oil,  and  are  colorless  liquids. 

Cumic  acid,  CeH4(C3H7)(COOH),  forms  plates  which  melt  at  160"* 
and  is  produced  by  the  oxidation  of  the  above  compounds. 

Thymol,  C6H3(OH)(CH0(C3H7),  thyme  camphor,  thyminic  acid,  is 
a  p-methylisopropyl  phenol,  and  occurs  with  cymene  and  thymene  in  oil 
of  thyme  and  forms  crystals  which  melt  at  51°  and  having  an  odor  simi- 
lar to  thyme.  When  fused  the  crystals  boil  at  230°  and  are  volatile 
with  steam.     Thymol  is  insoluble  in  water. 

Dithymoldi-iodide,(C3H7)(CH3)(IO)H2Ce-C«H2(OI)(CH3)(C3H7),aristol, 
is  produced  by  treating  an  alkaline  solution  of  thymol  with  an  iodine 
solution.     It  is  a  reddish,  odorless,  insoluble  powder. 

Carvacrol,  CjoHj^O,  isomer  of  thymol,  occurs  in  the  ethereal  oils  oi 
the  varieties  of  Origanum  and  Satureja.  It  forms  colorless  crystals  melt- 
ing at  0°.  It  is  produced  by  heating  camphor  with  iodine,  as  well  aj 
by  heating  the  isomeric  carvoe  (see  terpene  group)  with  phosphoric 
acid. 

Cantharidin,  C.^'R,^^^  or  C7H9(-CH2COOH)(-0-CO-),  a  lactone  acid 
(p.  404),  is  the  blister-producing  substance  of  the  Spanish  fly  (canthar- 
ides);  forms  crystals  which  melt  at  218°,  and  is  readily  converted  into 
the  isomer  cantharic  acid  and  on  heating  with  alkali  hydroxides  yields 
the  salts  of  cantharinic  acid,  CjqHj^Os,  which  is  unstable  when  free. 

Terpenes,  GjoHje.  These  compounds,  which  are  very  widely  dis- 
tributed in  nature,  will  be  discussed  at  the  end  of  the  isocarbocyclic  com- 
pounds, as  they  form  a  very  large  group  (analogous  to  the  carbohydrates). 
The  ketone  and  alcohol  derivatives,  the  camphors,  and  a  series  of  com- 
pounds derived  therefrom  will  also  be  discussed  at  that  time. 

m-Tolyloxybutyric  acid,  CHg-CeH.-CH-OH-C^H.-COOH,  forms  a 
lactone  (p.  404)  which  forms  the  active  principle  of  the  Indian  hemp 
called  cannahinol,  C21H26O2. 

Pentamethyl  benzene,  C^{CYL^^,  and 

Hexamethyl  benzene,  Ce(Cii3)e,  form  colorless  crystals.  (Preparation, 
p.  473.) 

Mellitic  acid,  Ce(COOH)e,  occurs  in  mellite  or  honey-stone,  Ce(COO)eAL, 
-M8H2O,  as  yellow  crystals  in  lignite  deposits.  Mellitic  acid  crystallizes 
in  white  needles  which  are  soluble  in  water  and  alcohol.  On  heating 
they  melt  and  at  higher  temperatures  they  decompose  into  pyromellitic 
acid,  C6H2(COOH)^  and  200,.  With  nascent  hydrogen  it  yields  hydro- 
mellitic  acid,  C6H6(COOH)6  (p.  463). 

Trinitro butyl  toluene,  C6H(N02)3(CH:,)(C^He),  forms  white  needles, 
which  occur  in  commerce  as  artificial  musk. 

lonone,  CjgHgoO,  obtained  from  citral  by  means  of  acetone,  and 

Irone,  C13H20O,  prepared  from  iridin  ^see  Glucosides),  give  the  odor  to 
the  violet-root  and  to  the  orris-root.     They  form  colorless  liquids  having 


504  ORGANIC  CHEMISTRY. 

the   odor  of  violets,  and  are  both  tetrahydrotrimethylbutylene  keton« 
benzenes,  C,H2(CH3)3(CH=CH  - CO-CH3)  (H,). 

COMPOUNDS  WITH  SEVERAL  BENZENE  RINGS. 

The  benzene  molecules  have  the  property  of  uniting  together  directly 
or  by  means  of  C  atoms  or  other  atoms.  The  hydrocarbons  thus  pro- 
duced, like  benzene,  are  the  starting-pomt  of  a  large  series  of  derivatives 
which  may  be  divided  into  the  followmg  four  groups. 

I.  Compounds  containing  Benzene  Rings  Directly  United. 

1.  Diphenyl,  CjgHio  or  HsCg-CeHs,  is  obtained  by  the  action  of  sodium 
upon  brombenzene.  It  crystallizes  in  colorless  crystals  and  forms,  like 
benzene,  the  starting-point  in  the  preparation  of  numerous  derivatives. 
By  the  action  of  the  halogens,  liJSOg  or  HglSO^,  upon  diphenyl  we  obtain 
mono-  and  disubstitution  products,  such  as  CiallgBr,  CigHg-SOgli, 
Ci2H.8(S03H)2,  CigHctNOg,  etc.  By  reduction  of  the  nitrouiphenyl  we 
obtain  amiuoaiphenyl,  (Jj2H9(NH2),  and  diamidodiphenyl,  C,2H^(NH2)2. 

Hexaoxydiphenyl.  (ilU).^d.2C8"~C8H2(OH)3,  is  the  mother-substance  of 
ccerulignone,  C^^H^qO^,  wliich  is  obtained  in  the  purification  of  crude 
wood-vinegar.     It  forms  blue  needles. 

7?-Diamidodiphenyl,  benzidine,  H2N-H4Ce-CeH4NH2,  is  produced  from 
the  isomeric  hydrazobenzene  by  molecular  rearrangement  and  forms 
the  mother-substance,  of  the  benzidine  dyes  (see  Azo  Compounds).  It 
is  also  used  in  the  quantitative  estimation  of  sulphuric  acid  as  insoluble 
benzidine  sulphate, 

(CeHrNH2)^2SO,. 

Phenyltolyl,  CeHg-CeH^CCHg),  is  produced  by  the  action  of  sodium 
upon  a  mixture  of  brombenzene  and  bromtoluene : 

CeH.Br  +  CjH.BrCCHg)  +  2Na= CeHe-C6H,(CH3)  +  2NaBr. 

It  forms  a  colorless  liquid  which  on  oxidation  yields 

Diphenyl  carbonic  acid,  CeHg-CgH^-COOH. 

Ditolyl,  (CHJCeH^-CeH^CCHg),  obtained  by  the  action  of  sodium  upon 
bromtoluene,  yields  on  oxidation 

Diphenyl  dicarbonic  acid,  (C00H)C6H,-CeH,(C00H). 

Diphenylenimide,   carbazole,   dibenzopynol,  C12H9N  or  <q«jj*>NH, 

occurs  in  coal-tar  and  is  obtained  from  o-diamidodiphenyl,  Cj2H8(NH2)2= 
C12H9N+NH3.     It  yields  carbazol  yellow. 

Diphenylenoxide,dibenzofurane,C,2HgOor  <c°h*^^'  ^®  derived  from 
dioxydiphenyl,  C,2H8(OH)2,  and  forms  colorless  crystals. 

Diphenylensulphide,  dibenzothiophene,  C,2HgS  or  <Q'fj^>S,  is  de- 
rived from  dithiodiphenyl,  Ci2H8(SH)2,  and  forms  colorless  crystal* 


J 


BENZENE  RINGS  UNITED  BY  ONE  C  ATOM,  505 


2.   Compounds  with  Benzene  Rings  united  by  One  Carbon  Atom. 

Diphenyl  methane,  Ci3H,2  or  CeHj-CH^-CeHs,  is  produced  by  warming 
benzylchloride  and  benzene  with  aluminmm  chloride  (p.  320); 

CeHsCH.Cl  +  C6He=  CeH^-CH^-CeH,  +  HCl. 

It  forms  colorless  needles  which  melt  at  26°  and  have  an  odor  similar  to 
oranges.  Its  derivatives  are  obtained  from  benzylchloride  and  toluene, 
xylene,  and  other  hydrocarbons,  also  with  phenols. 

CeHs-CH^Cl  -f- CeHgCCHg)  =  CeH^-CH^-  CflH^CCHg)  -}-  HCl ; 

Benzylchloride.  Benzyl  toluene. 

C6H,-CH2Cl  +  C6H5(OH)  =  CeHrCHrC6H,(OH)  +  HCl. 

Benzyl  chloride.  Benzyl  phenol. 

On  oxidation  these  hydrocarbons  are  converted  into  ketones,  where 
the  CHj  or  CH-CH3  groups  are  transformed  into  CO;  thus: 

g;H»>CH,    or    C.H,>cH-CH3    form    g;H'>CO. 

Diphenylmethane.  Diphenylethane.  Diphenylketone. 

If  the  benzene  nucleus  still  contains  alkyls  they  are  oxidized  to  carboxyl 
groups;   thus: 

CeHg-CH^-CeH/CHa)     forms    CeH^-CO-CeH^CCOOH). 

Benzyl  toluene.  Benzoyl  benzoic  acid. 

Diphenylcarbinol,  CeH5-CH(0H)-CfiH,j,  benzhydrol,  forms  crystals 
which  melt  at  68°  and  on  oxidation  yields 

Diphenylketone,  C^Hs-CO-CeHg,  benzophenone  (Preparation,  p.  498), 
forms  crystals  which  melt  at  27°.  It  forms  the  mother-substance  of  the 
yellow  dye  auramine,  C17H24N3HCI,  which  has  found  medical  use  and  of 
Michler's  ketone,  (CH3)2N-Il4C6-C0-C6H4-N(CH,)2,  which  is  used  in  the 
preparation  of  dyes  belonging  to  the  fuchsin  series  (p.  507).  The  yellow 
or  brown  plant  bodies,  maclurin,  C^^Hi^Oq,  of  fustic,  genistein,  0,^11, ^O^,  of 
dyers'  broom,  and  catechin,  C^^R^^O^,  of  catechu,  are  comphcated  ben- 
zophenone derivatives. 

C  H 

Diphenylenmethane,  fluorene,    <^«g<>CH2,   occurs  in  coal  tar  and 

forms  fluorescent  leaves.     (Structure,  see  p.  513.)  _r.  tr  _ 

Tetramethyldiamidodiphenylmethane,  (CH3)2N-C6H4  CHj  C«H^ 
N  (0113)2,  is  used  in  the  differentiation  of  ozone  from  other  gases  (p.  112). 

Triphenylmethane,  0,3,6  or  (OaH5)3  =  OH,  is  produced  by  heating 
benzal  chloride  and  benzene  in  the  presence  of  zinc  dust  or  alumin- 
ium chloride  (p.  320), 

OeH5-OH01,+  20eHe  =  OeHrCH(OeH5)3+2Ha, 


506  ORGANIC  CHEMISTRY. 

or  from  cliloroform  and  benzene  under  the  same  conditions: 

SCeHa-hCHClg  =  (CeH5)3  =  CH+3HCl. 

It  forms  colorless  leaves  melting  at  93°  and  boiling  at  360°.  It 
is  insoluble  in  water  and  on  oxidation  yields 

Triphenyl  Carbinol,  (06115)3 ^C~OH,  which  forms  colorless  prisms 
melting  at  159°. 

Triphenylmethane  and  triphenylcarbinol,  as  well  as  their  homo- 
logues,  form  beautifully  colored  derivatives  by  the  introduction  ol 
~0H,  ~NH2,  ~COOH,  which  are  generally  called  the  aniline  colors. 
This  misnomer  (p.  484)  arises  from  the  fact  that  the  anilines  are 
used  in  the  preparation  of  certain  of  these  dyes. 

Aniline  colors,  are  also  found  in  nature.  The  moUusk  Aplysia 
depilans  secretes  anihne  red.  The  red  and  blue  color  obtained  on 
allowing  food  to  stand  is  due  to  the  formation  of  aniline  colors  by 
means  of  bacteria  (blood  bread,  blue  milk,  etc.). 

The  dyes  of  this  group,  Hke  nearly  all  organic  pigments  (which  see), 
may  be  converted  into  colorless  leuco  compounds  by  reducing  agents, 
these  compounds  yielding  pigments  again  on  oxidation.  The  leuco 
bases  contain  one  O  atom  less  or  generally  two  H  atoms  more  than 
the  corresponding  pigment  base.  Leucaniline,  C20H21N3,  and  para- 
leucaniline,  C19H19N3,  the  leuco  bases  of  rosaniline  and  pararosaniline 
(see  below)  are  precipitated  from  their  salts  by  ammonia  and  form 
colorless  crystals. 

The  triphenylmethane  colors  may  be  classified  into  the  following 
groups: 

a.  Triamido  Derivatives  or  Rosaniline  Group. 

Rosaniline,  triamidodiphenyltolylcarbinol,  C2oH2oN3(OH)  or 
(H2N-H,Ce)2=C(OH)-CeH3(CH3) (NH2),  and 

Pararosaniline,  triamido  triphenylcarbinol,  Ci9Hi8N3(OH),  or 
(H2N-H4C6)2=C(OH)-(C6H4NH2),  the  free  bases  of  the  rosaniline 
dyes,  are  produced  when  the  solution  of  their  salts  is  treated  with 
caustic  alkali.  They  form  white  needles  which  combine  with  acids, 
forming  red-colored  salts  with  the  elimination  of  water.  Even  with 
CO2  of  the  air  pararosaniline  turns  red.  They  are  trivalent  bases 
stronger  than  NH3. 

Rosaniline  salts,  for  example,  CjoHjoNgCl,  and 

Pararosaniline  salts,  for  example,  Ci8H^gN3(C2H,02),  form  green, 


L'l^.v^^...^    ...iVCr      UNITED  Bl    Ui\ i.   C  A.OM.  507 

metallic-looking  crystals  which  are  mostly  soluble  in  water  and 
alcohol  and  occur  in  the  trade  as  fuchsm  and  aniline  red.  Their 
solutions  are  crimson  red  and  dye  animal  fibers  directly,  while  the 
vegetable  fibers  are  only  dyed  after  the  use  of  a  mordant  (p.  250). 

As  the  hydrogen  of  the  amido  groups  in  the  rosaniline  and  para 
rosaniline  salts  are  replaceable  by  alkyls  or  phenyls  it  is  possible  to 
obtain  various  colored  compounds. 

The  rosaniline  salts  are  obtained  by  the  oxidation  of  a  mixture  of 
analiiie  and  o-  and  p-tcluiuiu  (so  called  ainime  cJ)  vviih  arsenic  acid 
or  other  oxidizing  agents  with  the  aid  of  heat  until  the  mass  becomes 
metallic  in  appearance.  If  only  paratoluiaine  is  used,  then  the  para- 
rosaniline  salt  is  obtained: 

CflH^-NPI^  +  2C6H4(CH3)NH2  +  30  =  C^o-H^iNaO  +  2H2O. 

Aniiiue.  Toluidine.  Kosauiiine. 

The  arsenic  acid  is  reduced  to  arseniousacid,  which  then  forms  rosani- 
line arsenite.  This  is  removed  from  the  fused  mass  by  means  of  water 
and  the  solution  treated  with  salt,  when  rosaniline  hydrochloride  crys- 
tallizes out.  As  this  product  contains  arsenic,  nitrobenzene  has  recently 
been  suggested  as  the  oxidizing  medium,  it  taking  part  at  the  same  time 
in  the  formation  of  rosaniline: 

2CeH,(CIl3)  (NH,)  +  CeH,-NO,=  C,oH„N30  +  H,0. 
Toluidine.  Nitrobenzene.     Rosaniline. 

Aniline  blue,  Lyons  blue,  is  C2oHi7(C6Hj,)3N3Cl.  It  is  similar  to  gen- 
tian blue,  Parisian  blue,  Poirier's  blue,  spirit  blue,  and  is  produced  by 
introducing  phenol  groups  into  rosaniline  and  pararosaniline.  Its  com- 
pounds soluble  in  water  are  called  alkali  blue,  water  blue,  light  blue,  etc. 

Methyl  violet,  C,yHi2(CH3)6N3(Cl),  is  used  in  medicine.  Methylated 
rosanilines  are  called  Hoffmann's  violet,  crystal  violet,  dahlia  violet, 
while  methylated  pararosanilines  are  called  Parisian  violet  or  gentian 
violet. 

Methyl  green,  light  green,  is  CieH,2(CH3)6N3(Cl) +CH3CI. 

6.  Diamido  Derivatives,  or  (he  Malachite-green  Group. 

Malachite  green,  oil  of-bitter- almond  green,  is  derived  from  CeHj"" 
C(OH)=[CeH^~N (0113)2],  wliich  base  forms  with  zinc  chloride  or  oxalic 
acid  green  crystals  which  are  soluble  in  water.  The  homologues  of  this 
are  called  brilliant  green,  Victoria  green,  and  Helvetia  green. 

c.  Trioxy  Derivatives,  or  the  Rosolic  Acid  Group. 

Aurme,  CigHj^a  or  (C8H4-OH)o==C-C8H/0,  the  anhydride  of  trioxy- 
triphenylcarbinol,  (C6H/OH)2=0(OH)-  (OgH/OH),  is  soluble  in  alcohol 
and  acids,  forming  a  yellowish- red  solution,  and  in  alkalies,  producing 
a  fuchsin-red  solution.  It  is  prepared  from  pararosaniline  in  the  same 
way  as  rosolic  acid  is  obtained  from  rosaniline. 


508  ORGANIC  CHEMISTRY, 

Pittacal,  eupitton,  hexamethoxyaurine,  Cji,Hg(OCH3)808,  occurs  in 
beech-wood  tar.  

Rosolic  acid,  C20H16O3  or  (CeH/OH)2-=C-CeH3(CH3)(6),  dissolves 
in  alcohol  and  acids,  forming  a  yellow  solution,  and  a  red  solution  in 
alkalies.  It  is  prepared  by  the  action  of  nitrous  acid  upon  rosaniline, 
and  decomposing  the  diazo  compound  produced  by  means  of  water 
(p.  512). 

Corallines  are  the  red  (paonines)  and  yellow  dyes  produced  from  a 
mixture  of  aurine  and  rosolic  acid. 

d.  Carbonic  Acid  Derivatives,  or  the  Phthalein  Group. 

On  taking  up  2  H  atoms  these  compounds  are  converted  into  their 
leuco  derivatives,  the  phthalins;  thus,  phenolphthalein  into  phenol- 
phthalin,  fluorescein  into  fluorescin,  galle  n  into  gaUin,  etc. 

Phenolphthalein,  C^oH^ifii  or  (CeH,0H)2=C-CeHrC00,  obtained 
from  phthalic  acid  anhydride  and  phenol,  is  soluble  in  alcohol,  forming 
a  yellow  solution,  and  also  in  alkalies,  producing  a  beautiful  red  solution. 
Acids  decolorize  the  solutions. 

Tetraiodophenolphthalein,  CapHjoI^O^,  nosophen,  is  a  yellow  powder, 
almost  odorless,  used  as  a  substitute  for  iodoform.    

Fluorescein,  C^oH.A  +  H^O  or  0<^«][^3(0H)^(1_(>^jj^(.q(1)^  resorcin- 

phthalein,  is  obtained  from  phthalic  acid  anhydride  and  resorcin;  it  forms 
yellowish-red  crystals  which  are  soluble  with  a  yellowish  red  color  in 
alcohol,  and  red  with  alkalies  having  a  beautiful  green  fluorescence. 

Potassium  tetrabromfluorescein,  eosin,  C2oHcK2BrA,  colors  silk  yel- 
lowish red  with  a  fluorescence. 

TetraiodofluoresceVn,  erythrosin,  iodeosin,  dianthin,  py rosin,  CgpHgl.O,, 
are  used  as  indicators  (p.  87),  as  the  dilute  colorless  solution  in  etner 
turns  rose-colored  with  traces  of  alkali.  Other  eosin  colors  are  called 
phloxin,  primrose,  rose-bengal,  saf rosin. 

Gallein,  CgoHioOy,  pyrogaUolphthalein,  is  soluble  in  alkalies  with  a  blue 
color. 

Corulein,  CgoHsOg,  anthracene  green,  is  an  olive-green  soluble  dye 
obtained  from  gallefn. 

Rhodamine,  CasHgaNgOg,  a  beautiful  red,  fluorescent,  soluble  pigment. 

3.  Compounds  with  Benzene  Rings  United  by  Several  C  Atoms. 

Dibenzyl,  C8H5-CH2""CH2~CeH5,  S5nii-diphenylethane,  is  produced  by 
the  action  of  sodium  upon  benzyl  chloride  and  forms  large  prisms  which 
melt  at  52°  and  which  when  heated  to  500°  in  a  sealed  tube  yield  stilbene 
(see  below)  and  toluene. 

Hydrobenzoin,  C6H6-CH(OH)-CH(OH)-CaH5,  on  oxidation  yields 

Benzoin,  C8H5-CO-CH(OH)-C8H6.  so-caUed  oil -of-bitter  almond  cam- 
phor (p.  488) ,  and  on  further  oxidation  yields 

Benzil,  CeHg-CO-CO-CeHg,  diphenylketone  (see  p.  488). 

Stilbene,  CeHj-CH-CH-CeHg,  diphenylethylene,  toluylene,  is  pro- 
duced by  the  action  of  sodium  upon  benzalaldehyde. 


BENZENE  RINGS   UNITED  BY  N  ATOMS.  509 

Tolane,  H5C-C=C-C8H5,  diphenylacetylene,  is  obtained  from  stilbene 
bromide  by  boiling  with  alcoholic  caustic  alkali. 

Diphenyldiacetylene,  CeHs-C^C-C   C-CgH,,  and 

Hydrocinnamoin,  CeH5-CH=CH-CH  0H-CH0H-CH=CH-CeH6,  are 
examples  of  the  combination  of  two  benzene  rings  by  means  of  more  than 
two  C  atoms. 

Triphenylethylene,  (C6H5)CH=C(C6H6)2,  and 

Tetraphenylethylene,  (CcH6)2C=C(CcH5)2,  are  prepared  synthetically 
and  form  colorless  crystals. 

4,    Compounds  with  Benzene  Rings  United  by  Nitrogen  Atoms. 

Azoxy-,  Azo°-,  Hydrazo-Compounds.  The  aliphatic  nitro-com- 
pounds  are  directly  transformed  into  amines  by  reduction,  while  with 
the  cyclic  nitro-compounds  the  reduction  can  be  so  conducted  that  a 
series  of  intermediary  compounds  may  be  obtained.  Thus  on  reduc- 
tion in  acid  solution  (by  Fe  or  Zn+HCl  or  HjSOJ  we  obtain  amines; 
e.g.,  C6H5N02+6H=2H20+C6H5-NH2  (phenylamine) .  On  reduc- 
tion in  neutral  solution  (by  magnesium  or  aluminium  amalgam,  p.  243) 
hydroxylamine  compounds  are  obtained:  C6H5N02+4H  =  H20+ 
C6H5~NH'OH  (phenylhydroxylamine),  from  which  the  nitroso-com- 
pounds  are  obtained  on  oxidation  :  C6H5~NH*OH+0  =  H20+ 
C6H5~NO  (nitrosobenzene).  On  reduction  of  the  cyclic  nitro-com- 
pounds in  alkaline  solution,  depending  upon  the  reducing  agent 
(ammonium  sulphide,  sodium  amalgam,  sodium  methylate,  zinc- 
dust  and  caustic  alkali) ,  we  obtain,  before  the  formation  of  amines,  a 
series  of  intermediary  products  in  which  two  C  atoms  of  two  alphyls 
are  united  together  by  means  of  two  nitrogen  atoms  and  are  called 
azoxy-,  azo-,  and  hydrazo-compounds;   e.g., 

CeHj-NO,       CeHs-Nv  CeHrN        CeHs-NH       CeHrNH, 

l>0  II  I 

CeHs-NO^       CeHs-N/  CeHs-N        CeHs-NH       CeHs-NH, 

Nitrobenzene.       Azoxybenzene.        Azobenzene.     Hydrazobenzene.    Amidobenzene. 

The  azoxy-  and  azo-bodies  form  yellow  or  red  crystals,  while 
the  hydrazo-bodies  are  colorless.  All  three  groups  are  insoluble  or 
slightly  soluble  in  water  and  readily  soluble  in  alcohol,  and  are  of  an  in- 
different nature,  i.e.,  neither  acids  nor  bases.  Only  the  azo-compounds 
can  be  distilled  without  decomposition. 

The  azo-compounds,  the  most  important  of  these  compounds,  con- 
tain the  divalent  group  ~N"°N~,  formed  from  two  trivalent  nitrogen 


510  organlC  chemistry. 

atoms.  This  ""N'^N"  group  is  combined  by  each  of  its  bonds  with 
one  C  atom  of  a  cycUc  radical.  Mixed  azo-com pounds  containing  a 
cycUc  and  an  ahphatic  radical  are  known:  CH3'~N"N~C6H5,  azo- 
phenylmethyl. 

Compounds  are  also  known  which  contain  the  azo-group  "N'^N" 
two,  three,  or  four  times,  and  are  called  dis-,  tris-,  ^e^ra^o-compounds, 
e.g.,  C6H5-N=N-C6HrN=N-C,H4-OH,  disazobenzenephenol.  All 
azo-compounds  on  oxidation  yield  azoxy-compounds,  and  by  reduc- 
tion we  obtain  hydrazo-  and  then  amido-compounds. 

Besides  by  reduction  of  the  nitro-compounds,  they  are  also  ob- 
tained by  the  action  of  weak  reducing  agents  (sodium  amalgam) 
upon  azoxy-compounds,  or  by  the  oxidation  of  the  amidoazo-com- 
pounds,  which  may  be  obtained  from  the  diazo  compounds  (see  below). 

Azo  Pigments.  Many  of  the  so-called  coal-tar  or  aniUne  colors  are 
azo-compounds,  for  by  introducing  0H~  or  NHg  groups  into  azo-com- 
pounds we  obtain  bodies  having  the  properties  of  dyes  (seep.  530), 
producing  oxyazo-compounds :  C6H5~N^N"C6H4(OH),  C6H5~N^N~ 
C6H3(OH),,  etc.,  and  amidoazo-com pounds :  C6H5~N^N~C6H4(NH2), 
CgH5~N=N~C6H3(NH2)2,  etc.  By  the  introduction  of  alkyl  and  phenyl 
groups  into  these  compounds  they  change  from  yellow  or  red  color  to 
violet  or  blue.  On  the  introduction  of  NHj  or  OH  groups  we  produce 
from  the  indifferent  azo-compounds  derivatives  which  are  basic  or  acid 
in  character  and  have  the  property  of  combining  with  the  fiber  to  be 
dyed.  Many  azo  pigments  are  also  used  as  indicators  in  analytical 
chemistry  (p.  87).  The  azo  pigments  are  commercially  prepared 
by  the  action  of  cyclic  amines  or  phenols  upon  diazo-compounds 
(p.  512). 

The  hydrochlorides  of  amidoazo-com  pounds  are  orange  to  brown  in 
color  and  are  called  aniline  yellow,  chrysoiain,  phenylene  brown  (Bismarck 
brown,  vesuvin),  Manchester  brown,  etc.  The  alkali  and  ammonium 
salts  of  the  oxyazo-  and  amidoazo-com  pounds  are  orange,  red,  yellow,  or 
brown,  and  are  called  true  yellow,  helianthin,  methyl  orange,  resorcin 
yellow,  ethyl  orange,  tropa^olins,  etc. 

The  azo-compounds  of  naphthalene,  Cj  H„,  form  the  pigments  orange 
II,  ponceau,  true  red,  brilliant  black,  naphthalene  blue. 

Dis-,  tris-,  tetrazo  pigments  (see  above)  are  called  azoblack,  Biebricher 
scarlet,  crocein  scarlet,  etc.  Many  of  the  compounds,  especially  those  ob- 
tained from  naphthalene  with  benzidine,  diparamidodiphenyl,  (HgN)!!^^,- 
C6H4(NH2),  so-called  benzidine  pigments,  such  as  benzazurin,  benzopur- 

Eurin,  Congo  red,  chrysamine  yellow,  plso  c!iamin  black,  red,  and  brown, 
rilliant  yellow  (curcumin  w),  etc.,  differ  from  nearly  all  other  dyes  in 


DIA  ZO-COMPO  UNDS.  511 

that  they  dye  cotton  without  mordants  (substantive   dye)  and  hence 
have  replaced  the  other  dyes  more  and  more. 

Diazo=Compounds.  According  to  constitution  these  compounds 
do  not  belong  here,  but  on  account  of  their  relationship  to  the  azo- 
com pounds  they  will  be  discussed  at  this  place.  The  diazo- compounds 
contain  the  divalent  diazo  group,  >N  N,  formed  from  one  penta- 
valent  and  one  trivalent  N  atom,  which  is  combined  with  only  one 
valence  to  the  C  atom  of  one  cyclic  radical  and  the  other  valence  is 
combined  with  a  monovalent  group  (but  not  with  the  C  atom  of  the 
group  even  if  it  contains  C  atoms)  or  a  halogen;  e.g., 

H  n     V  III  XT  p     V    III  XT  p     V  III 

Diazobenzene  sulphate.      Diazobenzene  chloride.  Diazoamidobenzene. 

While  the  primary  aliphatic  amines,  by  the  action  of  nitrous  acid 
under  all  conditions,  replace  their  NH2  groups  directly  for  HO  groups 
(p.  378)  and  form  alcohols,  so  the  primary  cyclic  amines  (or  their  salts) 
when  strongly  cooled  (otherwise  phenols  are  produced)  yield  with 
nitrous  acid  in  the  presence  of  an  acid  (with  NaNOgH-  acid)  the  corre- 
sponding diazo  salts;  e.g.,  C,H5NH2vHCl)  +  HN02  =  (CeH5)(Cl)=N=N 
+  2H2O,  which  on  heating  with  water  yield  the  HO  derivatives,  the 
phenols;  e.g.,  (C0H5) (C1)=N  ^  N+  H^O  =  C«H5-0H+  2N+  HCl.  If 
nitrous  acid  is  allowed  to  act  in  the  absence  of  other  acids  (by  passing 
NO+NO2,  p.  156)  upon  cychc  amines,  diazoamido-compounds  are 
produced,  which  form  only  unstable  salts  with  acids,  but  which 
readily  rearrange  themselves  into  strongly  basic  amidoazo-com- 
pounds.  The  diazo  salts  may,  like  the  ammonium  salts  of 
(H0)HN=H3,  be  derived  from  their  basic,  very  unstable  diazohy- 
droxides,  e.g.,  from  (HO)(C6H5)N  — N,  and  may  therefore  also  be 
called  diazonium  salts. 

All  the  diazo-compounds  are  crystalline,  generally  colorless  solids, 
soluble  in  alcohol  and  insoluble  in  water.  They  explode  by  shock  or 
on  being  heated,  while  their  aqueous  solution  can  be  handled  with 
impunity.  They  are  extensively  used  in  the  preparation  of  azo 
pigments  (p.  512),  as  they  do  not  have  to  be  removed  from  their  solu- 
tion for  this  purpose. 

They  are  of  the  greatest  importance,  as  their  nitrogen  can  be 
readily  replaced  by  "H,  "Br,  "I,  "CI,  "OH,  "CN,  "NO^,  -SO3H,  "SCN, 
~OCN  (Gries's  reaction). 


512  ORGANIC  CHEMISTRY. 

The  nitrogen  of  the  diazo-compounds  can  be  replaced  in  the  following 
manner- 

1.  On  heating  with  water  they  yield  phenols  (p.  475). 

2.  On  heating  with  alcohols,  cyclic  hydrocarbons  are  produced: 

(N03)(CeH,)=N-N+C,HeO  =  CeHe  +  N,  +  C2H,0  +  HN03. 

3.  By  warming  with  CuBr,  CuCl,  CuCN,  the  diazo  group  is  replaced  by 
Br,  CI,  CN  (Sandmeyer's  reaction) : 

2(N03)  (CeH,)=N^N  +  2CuBr=  2C6H5Br  +  2CUNO3+ 2N. 

4.  With  reducing  agents  (p.  322)  they  yield  hydrazins: 

(Cl)(CeH,)=N=N  +4H=  (CeH5)HN-NH2  +  HCl. 

5.  On  heating  with  phenols  or  cyclic  amines  the  azo-compounds  (p.  510) 
are  produced: 

(Cl)(C6H,)=N=N+CeH5-NH,=  C6H5-N=N-C6H-NH2  +  HCl; 
(CI)(C6H5)=N=N  +  CeH50H  =  C6H5-N=N-CeH,-OH  +  HC1. 

6.  With  primary  or  secondary  cyclic  amines  diazoamido  compounds 
are  produced: 

(Cl)(C6H5)=N-N  +  CeH,-NH2-HCl4-(C6H,)(C6H5-NH)=N=N. 

The  nitrosamins  (p.  330)  as  well  as  the  isodiazo-compounds  are  isomeric 
with  the  diazo-compounds.  The  isodiazo-compounds  have  an  acid  char- 
acter and  do  not  yield  azo-compounds  with  phenols.  By  acids  they  are 
retransformed  into  diazo-compounds.  They  have,  like  the  azo-com- 
pounds, the  -N=N~  group  and  exist  in  two  stereoisomeric  forms,  as  syn 
and  anti  compounds  (p.  309).  The  first  are  obtained  by  the  action  of 
caustic  alkali  upon  diazo-compounds  and  are  very  unstable,  generally 
explosive,  and  are  quickly  converted  into  the  stable,  non-explosive  anti- 
isodiazo-compounds. 

Certain  isodiazo-compounds  are  also  known  among  the  aliphatic  com- 
pounds; thus,  isodiazoacetic  acid  ester,  (N=N)=CH-C00(CH)3  (p.  369.  4). 
This  ester  is  converted  by  caustic  alkali  into  salts,  (N=N)==CH-COONa, 
which  with  acids  decomposes  into  hydrazin  and  oxalic  acid: 

3  (N=N  )=CH-COONa  +  GH^O  +  3HC1  =  SN^H,  -f-  SC^H^O,  +  3NaCl 

(Preparation  of  the  Hydrazins,  p.  151). 

COMPOUNDS  WITH  CONDENSED    BENZENE  RINGS. 

Condensed  compounds  (p.  298)  and  their  derivatives  agree  com- 
pletely in  their  chemical  behavior  with  the  corresponding  benzene 
compounds.  The  following  compounds  contain  two  benzene  rings  with 
two  mutual  C  atoms: 


NAPHTHALENE  COMPOUNDS.  513 

Phenanthrene.  CuHio. 

H    H         H    H 
C=:C  C=C 

y     \      y      \ 
HC         C— C  CH 

\      ^      \      ^ 

c— c       c— c 

H     \^/    H 
C     C 
H    H 

Fluoranthrene,  CjjH^o,  pyrene,  CiaH,„,  chrysene,  Cij,Hi2,  naphtha- 
cene,  CigH,^,  picene,  C22H14,  all  have  a  similar  structure  and  are  found 
in  that  part  of  coal-tar  boiling  above  360°.  They  are  all  colorless 
crystals  and  their  derivatives  yield  even  a  larger  number  of  isomers  than 
the  benzenes. 

Condensed  compounds  of  benzene  rings  with  rings  poorer  in  C 
(p.  463)  which  have  two  mutual  C  atoms  are  also  known,  namely: 


Naphthalene,  CioHg. 

H        H 

Anthracene,  C14H10. 

H        H        H 

HC       C        CH 

1        II         1 
HC       C        CH 

H       H 

HC        C        C        CH 

1         II        II         1 
HC        C        C        CH 

^C^^C^^C^ 
H       H       H 

H 

H 

^\ 

HC       C- 

1         II 
HC       C 

^c^\ 

H 

Hydrindene 

H 

H 

nxj 

— CH, 

CH, 
C^ 

.  CgHlO. 

HC       C C       CH 

1        II          1        1 
HC       C        C        CH 

^c/\c/\c^ 

H       H,      H 

Fluorene,  C13H10. 

1            II            II 

HC       C        CH 

^c^c^ 

H        H, 

Indene,  CgHg. 

Besides  these  we  also  have  condensed  compounds  of  the  isocarbo- 
cyclic  with  the  heterocyclic  compounds  (see  the  latter).  Condensed 
compounds  which  consist  of  two  ring  systems  which  have  3  or  4 
mutual  atoms  are  also  known  (see  Terpenes  and  Alkaloids). 

I.  Naphthalene  Compounds. 

These  compounds  contain  two  benzene  rings  with  two  common 
C  atoms.  Naphthalene  may  yield  two  series  of  monosubstitution 
derivatives  (a  and  /?)  according  as  the  substituting  body  is  intro- 
duced next  to  one  of  the  two  hydrogen-free  C  atoms  or  removed  there- 
from, thus: 


514  ORGANIC  CHEMISTRY. 


H       X 

H       H 

H 

A\A\ 

/\y\ 

A\ 

HC7      C      2CH 

HC       C        CX 

HC       C-COOH 

HC6    c    sin 

HC       C        CH 

1         II 
HC        C-COOH 

^6  /\4^ 

\^\^/ 

\(/ 

H       H 

H       H 

H 

a-Componnds. 

;?-Compoimds. 

0  Phthalic  acid  (see  below 

If  in  naphthalene  two  hydrogen  atoms  are  substituted  by  the  same 
body,  then  ten  isomers  are  possible,  as  follows  making  use  of  the  figures 
given  above:  1:2;  1:3;  1:4;  1:5;  1:6;  1:7;  1:8;  2:3;  2:6;  2:7.  The 
positions  2:4  and  1:3;  2:5  and  1:6;  2:8  and  1:7  are  identical.  On  the 
substitution  by  different  bodies  the  number  of  isomers  is  still  greater. 

Naphthalene,  CigHg.  Preparation.  On  the  dry  distillation  of 
many  carbon  compounds,  especially  if  their  vapors  are  passed  through 
red-hot  tubes  (hence  it  is  a  chief  constituent  of  coal-tar).  On  cooling 
that  portion  of  coal- tar  boiling  between  210°  and  240°  impure  naph- 
thalene separates,  which  is  purified  by  subhmation. 

It  may  be  prepared  synthetically  in  many  ways;  thus  (analogous  to 
anthracene)  by  passing  the  vapors  of  phenylbutylene  over  red-hot  lead 
oxide:   C„H6-C,H;=C,oH3  +  4H. 

Properties.  Shining  colorless  plates  which  melt  at  80°  and  boil 
at  218°,  but  which  slowly  volatilize  at  15°  as  well  as  with  steam.  It 
has  a  peculiar  odor  and  a  burning  taste,  and  is  insoluble  in  water 
but  soluble  in  alcohol,  ether,  chloroform,  and  fatty  oils.  It  is  oxidized 
by  dilute  nitric  acid  into  orthophthalic  acid  (p.  497),  from  which  it 
fellows  that  this  acid  takes  the  ortho  position  (see  above).  This 
body,  and  hence  naphthalene  indirectly,  is  the  starting-point  in  the 
commercial  manufacture  of  artificial  indigo  (p.  548). 

With  concentrated  nitric  acid  we  obtain  mono-,  di-,  or  trinitro 
naphthalene,  depending  upon  the  extent  of  action.  These  nitro 
derivatives  are  readily  converted  by  reduction  into  the  correspond- 
ing amido  naphthalenes  (naphthylamines).  By  concentrated  sul- 
phuric acid  we  obtain  the  naphthalene  sulphonic  acids,  CjoH7~S03H, 
which  on  fusion  with  alkali  hydroxides  yield  the  naphthols,  CiqH/OH). 
Chlorine  first  produces  addition  products  rupturing  the  double  bonds 
of  the  C  atoms,  and  then  it  forms  substitution  products. 

Naphthols,  CioH7(OH).  On  heating  naphthalene  with  sulphuric  acid 
we  obtain  two  isomeric  naphthalene  sulphonic  acids,  CioH7(S03H),  which 


ANTHRACENE  COMPOUNDS.  515 

when  fused  with  alkali  hydroxides  yield  the  corresponding  naphthols. 
i9-naphthol  forms  colorless  plates  which  are  not  readily  soluble  in  water 
Dut  easily  soluble  in  alcohol.  It  melts  at  122°,  and  its  solutions  turn  green 
with  ferric  chloride  and  give  a  violet  fluorescence  with  MH3  and  a  white 
cloudiness  with  chlorine- water,  a-^^aphthol  is  much  more  poisonous  and 
melts  9 1  95°. 

/3-Naphthol  ethylether,  nerolin,  CioH7(0-C2H5),  has  an  odor  similar  to 
orange-flowers  and  is  used  as  a  perfume. 

/?-Naphthyl  benzoate,  benzonaphthol,  CeH5-COO(CioH;),  is  used  as  an 
intestinal  disinfectant. 

Amidonaphtholmonosulphonic  acid,  CioH5(OH)(NH2)(SO.^'H).  Its 
sodium  salt  is  used  as  a  photographic  developer  and  called  eikonogen. 

Calcium  /?-naphtholdisulphonate,  C,oHs(Oii)(S03)2Ca,  asaprol,  abrastol, 
is  a  non-poisonous  preservative  agent. 

Dinitronaphthol,  CioH5(N02)2(OH).  Its  sodium  salt  is  called  naphthalene 
yellow  or  Martius's  yellow.     Its  mlphonic  acid  is  called  naphthol  yellow. 

Naphthoquinone,  CjoHaO,,  occurs  in  the  volatile  form,  having  an  odor 
similar  to  quinone,  when  it  ii  designated  a,  and  an  odorless,  non-volatile 
form,  called  /?,  both  of  which  form  yellow  plates. 

Dioxynaphtho quinone,  C,„H^(OH)2U2,  napnthazarine,  alizarine  black, 
is  an  important  dyestufl". 

Acenaphthene,  C^oii^='C2ii.^,  occurs  in  coal-tar,  forming  colorless  prisms 
which  melt  at  95°. 

Santonin,  Ci-H^O.^,  the  active  principle  of  the  so-called  worm-seed,  is 
a  hexahydrodimethylen  naphthalene  derivative.  It  forms  colorless  bitter 
crystals  which  become  yellow  in  the  light,  melt  at  170°,  and  are  insoluble 
in  water  but  soluble  in  alcohol  and  chloroform.  When  dissolved  in  alka- 
lies it  forms  the  salts  of  santonic  acid,  CjgHooO^,  which  on  boiling  with 
baryta-water  is  converted  into  the  isomer  santoic  acid. 

Helenin,  C^^H^J^f,  alantol-lactone,  the  bitter  stuff  of  the  elecampane- 
root  (Inula  helenium),  is  a  naphthalene  derivative. 

Naphthalene  dyes.  Victoria  blue  is  a  dye  having  a  constitution  similar 
to  the  rosanilines,  and  naphthol  blue  like  the  indoaniline.  The  naph- 
thols and  naphthylamines  are  used  in  the  preparation  of  red,  reddish- 
brown,  and  brown  azo  dyes  (p.  510). 

2.  Anthracene  Compounds. 

These  compounds  contain  three  benzene  rings,  each  with  2  C  atoms 
in  common;  e.g., 

Anthracene,    C,,H^o,   or  H4C<^g>G6H,    (p.    513). 

Preparation.  It  is  produced  from  many  carbon  compounds  by 
heating  them  to  a  high  degree,  and  hence  it  occurs  in  that  portion 
of  coal-tar  having  a  high  boiling-point,  the  so-called  anthracene  oil 
(p.  473) ,  from  which  it  is  separated  from  the  isomeric  phenanthrenes 
by  distillation  with  potassium  carbonate,  and  from  phenanthrene 
by  treatment  with  carbon  disulphide,  which  only  dissolves  phenan- 


516  ORGANIC  CHEMISTRY. 

threne.  It  is  also  produced  in  the  distillation  of  alizarin  or  purpurin 
with  zinc-dust. 

It  may  be  prepared  synthetically  by  several  methods;  e.g.,  by 
passing  j>-benzyl toluene  over  heated  lead  oxide: 

/CH3  .CH. 

^CHrCeHs  \CH^ 

or  by  heating  benzene  with  tetrabromethane  and  AICI3  (p.  320) : 

BrCHBr  .CH. 

CeHe+      I         +CeH«  =  CeH,/|     >CeH,+  4HBr. 
BrCHBr  ^CH-^ 

Properties.  Scaly  crystals  having  a  bluish  fluorescence,  melting 
at  213°  and  boiling  at  360°.  They  are  insoluble  in  water  and  soluble 
with  diflSculty  in  alcohol  or  ether,  but  readily  soluble  in  benzene.  An- 
thracene is  not  nitrated  by  nitric  acid,  but  is  oxidized  to  anthraquinone. 

The  number  of  possible  isomeric  anthracene  derivatives  is  very 

great.     Three  mono  substitution  products  are  possible  and  fifteen 

disubstitution  derivatives  with  the  same  groups  are  possible,  etc. 

CO 
Anthraquinone,  diphenylendiketone,  C14H8O2  or  H4C6<p^>C6H4, 

is    produced    in    the   oxidation    of   anthracene    and    forms    yellow 

needles  which  melt  at  277°  and  yield  anthraquinone  sulphonic  acid, 

Ci4H702(S03H),  and  anthraquinone  disulphonic  acid,  Ci4H602(SOsH)2, 

with  fuming  sulphuric  awd. 

CO 
Alizarin,  dioxyanthraquinone,  Ci4Hg04  or  C6H4<pJ^>C6H2(OH)2. 

Occurrence.  Alizarin  is  a  coloring  matter  which  like  indigo-blue  does 
not  exist  already  formed  in  plants,  but  is  obtained  first  from  a 
glucoside,  ruberythric  acid,  which  is  contained  in  the  root  of  the 
madder  and  which  is  split  into  alizarin  and  glucose  by  fermentation  of 
the  powdered  root  or  by  treatment  of  the  same  with  dilute  acids 
or  alkalies: 

QoH^sOh     +     2H2O     =     C,4H^04    +     2CeH,20e. 

Ruberythric  acid.  Alizarin.  Glucose. 

Preparation.  In  the  past  it  used  to  be  prepared  from  powdered 
madder-root  (see  above),  but  at  the  present  time  alizarin  is  chiefly 


ANTHRACENE  COMPOUNDS.  517 

obtained  by  fusing  anthraquinone  sulphonic  acid  with  caustic  alkalies: 

CuH  ACSOgH)  +  2K0H  =  KHSO3+  HOH+  C,Ji,{OK)0,; 
ChH,(OK)0,+  KOH  =H2+C,,He(OK)202; 

which  last  compound  is  decomposed  by  HCl  into  alizarin. 

Properties.  Technical  aUzarin  is  a  yellowish-brown  paste,  and 
when  pure  it  forms  red  needles  which  are  not  readily  soluble  in  water 
but  readily  soluble  in  alcohol  and  ether,  producing  a  yellow  solution. 
It  behaves  like  a  substituted  diphenol,  as  an  acid  (p.  474),  and  dissolves 
in  alkalies  with  a  purple-red  color.  Aluminium  and  stannic  salts  form 
a  red  precipitate,  ferric  salts  a  dark-violet  with  solutions  of  alizarin 
(madder-lakes).  In  calico-printing  the  figures  are  printed  on  the 
material  with  the  above-mentioned  salts  and  the  goods  are  then 
dipped  into  water  in  which  ahzarin  is  suspended,  when  the  colored  com- 
pound of  aUzarin  with  the  metal  deposits  at  the  place  mordanted. 
If  cotton  is  mordanted  with  alum  and  oil  then  alizarin  produces 
the  beautiful  turkey-red  color. 

Aloin,  of  the  aloes,  which  differs  according  to  the  variety  of  aloes, 
also  called  barbaloin,  CigHjeOy  +  SHgO,  capaloin,  CieHjeOy,  nataloin, 
CieHigOy,  all  of  which  are  derivatives  of  anthraquinone. 

Methj^ldioxyanthraquinones,  Ci4H5(CH3)(OH)202  or  CigH^oO^.  One 
of  these  is  the  chrysophanic  acid  which  is  found  in  the  senna  leaves,  in 
the  root  of  the  rhubarb,  and  in  certain  lichens.  It  forms  golden-yellow 
needles  which  are  soluble  in  alkalies  with  a  purple-red  color.  Chrysarobin, 
CauHogOy,  the  active  constituent  of  the  drug  called  Goa  or  Arroroba 
powder.  It  is  a  yellowish  crystalline  powder,  which  is  not  readily  soluble 
in  water  and  ammonia,  but  forms  a  yellow  solution  with  caustic  alkalies. 
On  shaking  the  alkaline  solution  with  air  it  turns  red  and  contains  then 
chrysophanic  acid:  C3oH2607  +  40=2CjsHio04  +  3H20. 

Trioxyanthraquinones,  Ci4H6(OH)302.  One  of  these,  called  purpurin, 
occurs  with  alizarin  in  the  roots  of  the  madder  and  may  be  formed  from 
alizarin  by  oxidation.     It  dyes  wool  in  a  similar  manner  to  alizarin. 

Methyltrioxyanthraquinones,  0,^114(011)3(0113)02.  One  of  these, 
emodin,  occurs  in  the  rhubarb  roots,  aloes,  bark  of  the  black  alder,  and 
in  senna  leaves.     It  forms  orange-yellow  needles. 

Methyltetraoxyanthraquinones,  01^113(0113)  (0H)^02.  One  of  these, 
rhein,  occurs  sometimes  with  emodin. 

Anthracene  dyes.  Many  artificial  dyes  are  derived  from  alizarin  by 
introducing  -OH  and  NHg  groups,  producing  alizarin  carmin,  alizarin 
orange,  alizarin  blue,  alizarin  bordeaux,  alizarin  cyanin,  alizarin  green, 
flavopurpurin,  anthrapurpurin,  anthracene  blue,  anthracene  brown. 


.618  ORGANIC  CHEMISTRY. 


3.  Phenanthrene  Compounds. 

These,  like  the  anthracene  compounds,  contain  three  benzene  nuclei 
with  two  common  C  atoms. 

/CgH^-CH 
Phenanthrene,  Ci.Hio  or  <  ||      (structure,  p.  513),  is  obtained 

from  many  carbon  compounds  at  a  white  heat,  and  hence  occurs  in  coal- 
tar  with  anthracene  (separation,  p.  515)  and  also  by  heating  benzofurane 
(p.  550)  with  benzene: 

/CH^  /C«HrCH 

CcH/        >CH+C6He=^  II     +HA 

It  forms  colorless  crystals  which  melt  at  89°  and  boil  at  340°,   and 

.CeH,-CO 
on  oxidation  yields  phenanthraquinone,  <  |     ,  and  then  diphenic 

^CeH.-CO 

acid,  <c*H*-COOH  (^-biphenyldicarboxyl  acid). 

Retene,  Ct^Hig,  methylisopropylphenanthrene,  occurs  in  the  tar  from 
coniferae  and  certain  earith  resins,  and 

Perhydroretene,  CikH^j,  fichtelite,  contained  in  the  turf  from  fossil 
pines;  both  form  colorless  crystals. 

4.  Indene  and  Fluorene  Compounds. 

These  contain  benzene  and  pentamethylene  rings  (p.  464)  with  common 
C  atoms  (structure,  p.  513). 

Indene,  CgH^,  occurs  in  coal-tar  and  is  a  hquid,  boiling  at  1£0°  and 
having  an  odor  similar  to  naphthalene  and  yielding  o-phthalic  acid 
(p.  514)  on  oxidation.  Its  name  is  derived  from  the  fact  that  on  sub- 
stituting an  =CH2  group  of  indene  by  =NH  we  obtain  indol  (p.  547). 

Hydrindene,  CgH,,,,  accompanies  pseudocumene  (p.  49C)  and  is  pro- 
duced by  the  action  of  nascent  hydrogen  upon  indene.     It  boils  at  177°. 

Fluorene,  CigHjo,  has  already  been  discussed  on  p.  505. 

Carminicaci(i,C24H220,4.  carmine  red,  contains  probably  two  hydrindene 
derivatives  in  the  molecule.  It  occurs  in  the  flowers  of  the  i  -onarda  didyma, 
in  cochineal,  in  the  kernies  berries,  and  forms  red  masses,  which  are  soluble 
in  water  and  alcohol,  with  a  yellowish-red  color  and  which  turn  crimson 
red  in  the  presence  of  alkalies.  The  carmine  of  commerce  is  a  clay  lake 
(p.  250)  of  carminic  acid. 

Compounds  of  the  Terpene  Group. 

This  group  includes  the  terpenes  and  the  varieties  of  camphors. 
Terpenes  are  the  isomeric  hydrocarbons  having  the  formula  CigHig, 
or  their  polymers  which  are  either  dihydrocyraencs  (p.  519)  or  are 
camphenes.  The  latter  have  a  benzene  ring  in  which  two  C  atoms 
are  united  bridge-like  with  another  C  atom. 


COMPOUNDS  OF   THE   TERPEN E  GROUP. 


519 


The  terpenes  contain  only  one  or  two  double  bonds  between 
the  C  atoms  in  the  benzene  ring,  so  that  only  two  or  four  univalent 
atoms  or  groups  of  atoms  can  be  attached  thereto,  when  all  the  C 
atoms  of  the  benzene  ring  will  have  single  bonds. 

The  terpenes  are  also  hydrocarbocyclic  and  hence  also  alicyclic 
compounds  (p.  327),  the  camphors  are  terpenes  or  hydroterpenes  with 
a  ketone  or  alcohol  group,  which  generally  contains  the  C  atoms  in 
the  benzene  ring  with  single  bonds.  Camphors  with  several  ketone 
or  alcohol  groups  are  not  known  in  nature  but  may  be  prepared 
synthetically. 

The  terpenes  and  camphors,  which  are  derived  from  the  dihydro- 
cymenes  are  called  terpanes,  as  ihey  may  also  be  derived  from  hexahydro- 
cymene  or  terpane,  CjoHao-  The  terpenes  and  camphors  which  are  derived 
from  the  camphenes  are  called  camphanes,  as  they  may  also  be  derived 
from  dihydrocamphene  or  camphane,  CjoH^g. 

We  also  know  of  aliphatic  compounds,  isomeric  with  the  terpenes 
and  camphors,  which  like  these  occur  in  the  ethereal  oils  (see  below) 
and  which  are  called  olefinic  terpenes.  These  can  be  readily  transformed 
into  cyclic  terpenes  (p.  445). 

As  the  variation  in  structure  cannot  be  shown  with  most  of  these 
bodies  having  the  same  empirical  formula,  it  is  very  difficult  to  give  a 
structural  formula  for  them.  The  following  formulae  show  the  relation- 
ship that  certain  of  these  compounds  bear  to  each  other: 


H,C 


CH3 


H,C 


CHa 


CH 

h 
/\ 

HC        CH 

Hi        L 

\/ 

C 

I 
CH3 

Cymene,  C10H14. 


V 

in 

HgC        CHj 
HC        CHa 

Y 

CH3 

Limonene,  CioHje. 


H3C  CH3 

CH 

I 
CH 

H^C         CH(OH) 
HgC         CHj 

CH 

I 
CH3 

Menthol,  C10H20O. 


CH, 

I- 


-CH 


CH, 
-C — 


-CO 


H,C-C-CH, 


H,C- 


-CH CH 


H3C-C-CH, 


H,C-C- 


CH3 

-C CO(OH) 


-CH CH,       H^C 


Camp  bene ,  CioHie. 


Camphor,  CioHieO. 


CH, 

;h — co(OH) 

Camphoric  acid .  CioHieO*. 


520  ORGANIC  CHEMISTRY. 

Contrary  to  the  other  isocarbocycHc  compounds  the  atoms  are  in 
very  unstable  equilibrium,  so  that  the  various  compounds  can  very  readily 
be  transformed  into  each  other  and  the  ketones  may  also,  by  displace- 
ment of  the  atoms,  be  converted  into  acids.  That  also  cymene  can  be 
split  off  from  compounds  of  the  second  series  depends  upon  the  fact  that 
by  the  chemical  action  the  C  atoms  on  the  dotted  lines  are  separated  pro- 
ducing an  isopropyl  group  in  the  p-position  to  the  methyl  group. 

The  terpenes  boil  at  160°-190°  and  their  boiling-points  are  so  close 
together  that  they  cannot  be  separated  by  fractional  distillation, 
while  this  can  be  done  on  the  contrary  by  their  ability  of  forming 
well-defined  crystalHne  compounds  with  HCl,  HBr,  Brj,  or  N2O3. 
These  compounds  may  be  differentiated  by  their  different  melting- 
points.  They  are  distinguished  as  terpenes,  CjoHie,  sesquiterpenes, 
C15H24,  diterpenes,  C20H32,  and  polyterpenes,  {Q>^^^f)x,  and  form  (with 
the  exception  of  the  camphenes  and  the  polyterpenes,  which  are 
solids)  colorless  liquids  having  characteristic  odors.  They  have  differ- 
ent boihng-points,  various  densities,  great  difference  in  their  odor, 
and  are  most  of  them  optically  active. 

Nearly  every  terpene  has  a  known  dextro-  and  Isevorotatory 
modification,  from  which  an  optically  inactive  form  (p.  39)  may  be 
obtained  by  mixing  equal  parts  of  each.  By  repeated  distillation 
or  shaking  with  small  amounts  of  concentrated  sulphuric  acid  inactive 
or  polymeric  terpenes  are  produced.  On  heating  with  iodine  many 
yield  cymene,  CioHi64-2I  =CioHi4+2HI,  and  on  oxidation  with  dilute 
nitric  acid  they  yield  p-toluic  acid,  C6H4(CH3)(COOH),  and  tere- 
phthalic  acid,  CoH4(COOH)2,  which  are  also  obtained  on  the  oxidation 
of  cymene  (p.  503).  The  terpenes  inflame  by  the. energetic  action  of  the 
halogens  as  well  as  by  nitric  acid.  They  also  readily  absorb  oxygen 
from  the  air  and  are  converted  into  acids,  as  well  as  solids,  which  have 
great  similarity  to  the  natural  resins.  By  addition  of  HCl  the  ter- 
penes, CioHjg,  produce  the  hydrochlorides,  CjoHj^Cl,  which  readily 
replace  the  CI  for  ~0H  and  are  transformed  into  the  corresponding 
camphors. 

The  camphors  (terpene  alcohols  and  terpene  ketones)  are  opti- 
cally active  and  generally  form  crystals,  and  seldom  liquids,  having 
a  characteristic  odor.  The  alcohol  camphors  can  have  their  HO  groups 
readily  replaced  by  CI,  and  the  chlorine  derivatives  are  easily  trans- 
formed into  terpenes  by  the  action  of  alcoholic  caustic  alkali,  splitting 
off  HCl.  The  HO  groups  are  also  replaceable  by  NHg,  producing 
amine  bases.    The  ketone  camphors  are  converted  into  alcohol  cam- 


COMPOUNDS  OF  THE  TERPENE  GROUP.  521 

phors  by  nascent  hydrogen,  and  these  latter  yield  ketone  camphors 
on  oxidation  with  potassium  bichromate  and  sulphuric  acid. 

The  terpenes  occur  generally  mixed  together  in  many  plants 
and  form  the  odoriferous  principles  of  the  same,  namely,  the  ethereal 
oils.  The  camphors  also  occur  in  many  plants,  especially  dissolved 
in  the  ethereal  oils  of  the  given  plant.  Many  terpenes  and  camphors 
can  be  obtained  only  synthetically. 

Ethereal  oils  is  the  name  given  to  a  large  number  of  organic  com- 
pounds occn.rring  in  the  vegetable  kingdom.  On  account  of  their  volatility 
they  can  be  obtained  fro\n  the  respective  plants  by  distillation  with  steam. 
They  have  a  specific  odor  and  a  burning  taste,  and  are  most  of  them  liquid 
at  ordinary  temperatures  and  nearly  insoluble  in  water.  They  have  no 
relationship  to  the  actual  oils  (fats),  and,  with  the  exception  of  the  etliereal 
oils  produced  from  the  terpenes,  form  no  connecting  groups.  They  are 
extensively  used  in  perfumery,  medicine,  and  in  the  preparation  of  cor- 
dials. 

Nearly  all  ethereal  oils  rotate  the  polarized  ray  of  light  and  produce  a 
temporary  transparent  spot  on  paper  and  cotton  material.  The  name 
ethereal  oils  is  derived  from  this  last  property  and  from  their  often 
oily  consistency,  as  well  as  their  volatility.  They  are  readily  soluble  in 
alcohol,  ether,  chloroform,  and  fatty  oils,  and  burn  with  a  smoky  flame. 
They  absorb  oxygen  from  the  air  and  thicken,  being  converted  into  resins, 
or  are  transformed  into  acids. 

The  solids  obtained  from  the  ethereal  oils  by  cooling  were  formerly 
called  stearoptenes,  and  the  liquid  remaining  called  eldoptenes. 

On  rubbing  1  part  of  an  ethereal  oil  with  50  parts  powdered  sugar,  we 
obtain  what  is  called  oil-sugar. 

Oxygen-free  ethereal  oils  consist  nearly  entirely  of  terpenes;  e.g.,  oil 
of  turpentine,  oil  of  savine,  oil  of  bergamot,  oil  of  lavender,  oil  of  rosemary, 
oi:l  of  orange-flowers,  oil  of  calamus,  oil  of  juniper,  etc. 

The  ethereal  oils  containing  oxygen  are  mixed  in  the  crude  state  with 
small  or  large  quantities  of  terpenes.  They  consist  of  alcohols,  aldehydes, 
phenols,  compound  ethers,  camphors,  etc.,  which  are  split  off  in  their  prepa- 
ration by  the  steam  from  the  esters  or  ethers  of  peculiar  alcohols  (the 
oUols)  contained  in  the  various  plants.  To  this  group  belongs  the  oil  of 
bitter  almond,  which  contains  benzaldehyde,  oil  of  cinnamon,  which  con- 
tains cinnamic  aldehyde,  oil  of  wintergreen,  which  contains  methyl  sali- 
cylate. Oil  of  anise  contains  anethol,  oil  of  fennel  contains  fenchone,  oil  of 
cajuput  contains  cajuputol,  oil  of  nutmeg  contains  myristicol,  CjoHjgO, 
oil  of  caraway  contains  carvol,  C,oH,^0,  oil  of  cloves  contains  eugenol,  oil 
of  peppermint  contains  menthol,  oil  of  thyme  contains  thymol,  oil  of  rose 
contains  geraniol,  oil  of  lemons  contains  besides  terpene  also  linalool, 
citral,  and  citronellal,  oil  of  sandal-wood  contains  besides  santalene  also 
santalol,  CigH.^eO.     See  also  p.  445. 

The  ethereal  oils  containing  sulphur  are  compounds  of  alcohol  radicals 
with  ~NCS  or  with  sulphur;  thus,  mustard  oil  contains  isosulphocyan- 
allyl,  oil  of  garlic  and  oil  of  onions  contain  allyl  sulphide,  etc. 


522  ORGANIC  CHEMISTRY, 


I.  Terpenes. 

The  camphanes,  to  which  pinene,  camphene,  fenchene,  belong,  can  take 
up  by  addition  1  mol.  HCl,  HBr,  or  Brg  (p.  519);  the  terpanes,  such  as 
linomene,  terpinolene,  sylvestrene,  can  take  up  2  mols.  HCl,  HBr,  Bfj; 
while  the  terpanes  phellandrene  and  terpines  take  up  only  N^Og. 

Pinene  boils  at  156°.  l-l  inene,  terebentene,  occurs  in  the  German, 
French,  and  Venetian  turpentine  oil,  Canada  balsam,  incense,  and  many 
ethereal  oils.  d-Pinene,  or  australene,  occurs  in  English  and  American 
turpentine  oil  and  also  in  many  ethereal  oils,  i-tinene  is  produced 
synthetically. 

Pinenehydrochloride, CioHjg.HCl, is  produced  bypassing  HCl  gas  into 
pinene,  forming  crystals  having  an  odor  similar  to  camphor,  and  is  called 
artificial  camphor." 

Turpentine  oil  is  obtained  from  the  turpentine,  which  exudes  from 
various  conifers?,  by  distillation  with  water.  It  is  a  colorless  liquid 
having  a  peculiar  odor  boiling  at  160°  and  which  is  insoluble  in  water  but 
soluble  in  alcohol,  ether,  and  fatty  oils.  It  dissolves  sulphur,  phosphorus, 
resins,  and  caoutchouc.  On  distilling  with  lime-water  we  obtain  rectified 
oil  of  turpentine,  which  is  free  from  acids  and  resins.  When  exposed  to 
the  air  turpentine  oil  absorbs  oxygen  and  becomes  resinous  (used  in  the 
preparation  of  resin  varnishes  and  oil-paints). 

Terebene,  a  mixture  of  inactive  terpenes,  is  produced  by  the  action  of 
sulphuric  acid  upon  turpentine  oil  and  subsequently  distilling  with  steam. 
It  smells  like  thyme. 

t-,  d-,  Z-Camphenes  are  produced  by  the  action  of  alkalies  upon  i-,  rf-, 
Z-pinene  hydrochloride  and  are  colorless  crystals  melting  at  about  50°, 
having  an  odor  similar  to  camphor. 

i-Fenchene,  obtained  from  fenchone  (p.  524),  boils  at  about  160°. 

Limonene  (structure,  p.  519)  boils  at  175°.  d-Limonene,  citrene,  car- 
vene,  cajeputene,  hesperidene,  smells  like  lemons  and  occurs  in  oil  of  dill, 
caraway,  orange-flowers,  bergamot,  and  lemons. 

Z-Limonene  occurs  with  /-pinene  in  pine-needle  oil. 

t-Limonene,  dipentene,  cinene,  boils  at  180°,  and  is  found  with  syl- 
vestrene in  Swedish  and  Russian  turpentine  oil,  in  camphor  oils,  and  oil 
of  Cinse,  etc.  It  is  produced  on  heating  the  active  limonenes  to  300°  or 
by  splitting  off  water  from  terpine  hydrate. 

z-Terpinols  are  formed  by  boiling  terpine  hydrate,  terpineol,  cineol,  with 
dilute  sulphuric  acid.     Boil  at  IT 5°. 

cZ-Sylvestrene,  the  chief  constituent  of  Swedish  oil  of  turpentine,  boils 
at  176°. 

t-Sylvestrene,  carvestrene,  is  prepared  synthetically. 

Phellandrene  boils  at  170°.  d-Phellandrene  occurs  in  ethereal  oil 
of  fennel,  water-fennel,  elemi,  oil  of  eucalyptus;  Z-phellandrene  also  occurs 
in  the  two  last-mentioned  oils. 

i-Terpinene  is  produced  by  boiling  most  terpenes  with  dilute  sulphuric 
acid.     Boils  at  180°,  and  smells  like  lemons. 

2.  Sesqui=,  Di=,  Polyterpenes. 

Cedrene,  cardinene,  clovene,  caryophyllene,  santalene,  are  sesqui- 
terpenes, C15H24,  and  occur  in  the  ethereal  oils  of  cubebs,  savine,  patchouli, 
and  santal.      Ihey  boil  between  250°-280°. 


CAMPHORS.  623 

Colophene,  retinol,  are  both  diterpenes,  C20H32,  are  found  in  balsam 
of  copaiba,  are  produced  by  the  distillation  of  rosin,  and  boil  above 
300°. 

Caoutchouc  (India-rubber),  the  dried  juice  of  the  tropical  Euphor- 
biacse,  Apocynse,  etc.,  and 

Gutta  percha,  the  dried  juice  of  the  tropical  Sapotacese,  both  bodies 
polyterpenes,  (C,oHi6)n,  are  nearly  insoluble  in  alcohol,  but  soluble  in  CSj, 
CHCI3,  CgHe,  and  turpentine  oil.  At  ordinary  temperatures  they  are 
tough  and  elastic,  and  in  the  cold  they  become  hard. 

The  elasticity  of  caoutchouc  is  increased  by  introducing  sulphur 
(vulcanization).  Vulcanized  rubber  contains  2-4  per  cent,  sulphur. 
If  the  quantity  of  sulphur  is  increased,  then  the  rubber  becomes  hard, 
homy,  and  is  used  as  ebonite,  or  vulcanite,  for  the  making  of  combs,  probes, 
electrical  machines,  etc. 

Rolled  gutta  percha  is  called  gutta-percha  paper.  Purified  gutta 
percha  is  white  and  generally  occurs  in  rolls. 

3.  Camphors. 

Bomeol,  fenchone,  thujone  have  a  camphene  structure,  while  the 
others  have  a  cymene  structure. 

a.  Camphors  C^^^^O. 

Carvone,  carvol,  the  ketone  of  limonene  (p.  522),  the  isomer  of  car- 
vacrol  (p.  503),  boils  at  225°. 

d-Carvone  is  found  in  the  ethereal  oil  of  dill  and  caraway. 
Z-Carvone  occurs  in  the  ethereal  oil  of  curomoji. 

h.  Camphors  C^^fi. 

d-Camphor,  Japan  camphor,  laurinene  camphor,  is  a  ketone  (p.  519) ;  it 
occurs  in  the  tree  l.aurus  camphora,  and  is  obtained  therefrom  by  subli- 
mation. It  forms  white  crystalline  masses  having  a  characteristic 
odor  and  burning  taste.  It  is  volatile  at  ordinary  temperatures,  melts 
at  175°,  and  boils  at  204°.  Camphor  is  insoluble  in  water,  readily 
soluble  in  alcohol  (spirits  of  camphor),  in  ether,  acetic  acid,  ethereal  and 
fatty  oils.     A  solution  in  olive- oil  forms  the  camphorated  oil. 

Z-Camphor,  in  ethereal  oils  of  Matricaria  Parthenium,  is  produced  on 
oxidizing  Z-borneol. 

On  warming  a  solution  of  camphor  with  sodium  we  obtain  sodium 
camphor  and  sodium  bomeol:  2CioH,60  +  2Na  =  CioH,5NaO  +  C,oH,7NaO, 
which  are  decomposed  by  water  into  caustic  soda,  camphor,  and  d-borneol, 
C,oHi,0  (p.  524). 

By  dehydrating  agents  (PgOg,  ZnClg,  PgSs)  camphor  is  converted 
into  cymene:    CioHieO^CioH^^  +  HaO. 

Heated  with  iodine  camphor  is  transformed  into  the  cymene  phenol, 
carvacrol  (p.  503),  C,oH,,0:    C,„Hi60  +  2I=C,oHi,0  +  2HI. 

Oxy camphor,  CjjHieOj,  forms  colorless  crystals  which  are  soluble 
in  50  parts  water  and  which  smell  like  pepper. 

Camphoric  acid,  CioHgO^  (structure,  p.  519),  is  produced  besides 
camphanic  acid,  CioHieOg,  and    camphoronic   acid,  CjHi^Oe,  on    boiling 


524  ORGANIC  CHEMISTRY, 

camphor  with  HNO3,  and  forms  colorless  and  odorless  crystals  which  melt 
at  186°  and  are  not  readily  soluble  in  cold  water,  but  easily  soluble  in 
alcohol  and  ether. 

Alantole,  alant  camphor,  in  the  roots  of  the  Inula  Helenium. 

Fenchone,  in  the  ethereal  oil  of  fennel  and  oil  of  thuja. 

Absinthole,  wormwood  camphor,  in  the  ethereal  oil  of  wormwood. 

Myristicol,  in  the  ethereal  oil  of  the  nutmeg. 

Thujone,  tanacetone,  in  the  ethereal  oil  of  thuja. 

Sabinole  in  the  ethereal  oil  of  savine. 

c.  Camphors  C^^llifi. 

d-Bomeol,  Borneo  camphor,  occurs  in  the  Dryobalanops  camphora 
tree,  in  the  ethereal  oil  of  rosemary  and  spike.  It  differs  from  the  Japan 
camphor  by  its  crystalline  form,  by  being  harder,  melting  at  208°,  and 
boihng  at  212°.  It  is  the  alcohol  corresponding  to  the  Japan  camphor 
and  is  produced  therefrom  by  the  action  of  nascent  hydrogen  or  of  sodium 
(see  above),  and  is  converted  into  Japan  camphor  by  mild  oxidation. 
Z-Borneol  occurs  as  Ngai  camphor  obtained  from  the  Blumea  balsam- 
ifera  as  well  as  with  i-borneol  in  certain  ethereal  oils. 

Cineol,  eucalyptol,  cajeputol,  occurs  in  the  ethereal  oils  of  encalyptus, 
cajeput,  worm-seed,  and  is  a  colorless,  inactive  liquid. 

Menthon  is  produced  by  oxidizing  menthol  (see  below). 

Terpineol  is  contained  in  various  ethereal  oils,  melts  at  37°,  and 
smells  like  lilac  flowers. 

d.  Camphors  G^fi^fi,  Q^^^fiy 

Menthol,  menthol  camphor,  CjoHjoO  (structure,  p.  519),  is  obtained 
from  peppermint-oil  by  strongly  cooling,  when  it  separates  out.  It  forms 
colorless  crystals  having  a  melting-point  of  43°.  It  yields  the  ketone 
menthon,  CiqHisO,  on  oxidation,  and  menthen,  CjoHjg,  on  sphtting 
off  of  HgO.  Menthol  valerianate,  called  validol,  is  used  in  medicine. 
The  chlormethyl  menthyl  ether,  CjoHi9(CH2Cl)0,  is  called  forman  and 
decomposes  with  water  into  menthol,  formaldehyde,  and  hydrochloric 
acid. 

Terpine  hydrate,  CioH2o02-f-H20,  is  produced  by  allowing  pinene,  ter- 
pineol, or  linalool  to  stand  in  contact  with  dilute  mineral  acids,  as  well 
as  from  terpine,  by  the  action  of  water,  and  from  oil  of  turpentine  by  the 
action  of  alcohol  and  nitric  acid.  It  forms  colorless  and  odorless  crystals 
which  are  soluble  with  difficulty  in  water,  ether,  chloroform,  but  readily 
soluble  in  alcohol,  and  melti'^g  at  116°,  when  it  loses  water  (formation  0/ 
terpine),  and  the  melting-point  falls  to  102°. 

Terpine,  C10H20O2,  is  produced  by  continuously  warming  terpine  Hy- 
drate. 

4.  Resins 

is  the  name  given  to  a  number  of  amorphous,  brittle,  yellowish  to  brown 
bodies  of  unknown  constitution  which  contain  only  C,  H,  O,  which  are 
closely  related  to  the  terpenes  and  which  occur  with  these  in  the  plants 
and  perhaps  formed  from  the  terpenes  by  oxidation  in  the  air.     They 


RESINS.  525 

consist  of  an  indefinite  amount  of  ethereal  oils,  etc.,  and  a  mixture  of 
resins  which  are  difficult  of  separation.  Chemically  they  act  like  acids, 
they  dissolve  in  alkalies,  forming  so-called  resin  soaps,  which  form  a 
lather  like  soaps  and  from  which  the  resins  are  precipitated  by  acids. 
They  cannot  be  distilled  without  decomposition  and  they  burn  with  a 
luminous  flame. 

On  fusion  with  alkalies  most  of  the  resins  yield  protocatechuic  acid, 
phloroglucin,  paraoxy benzoic  acid,  pyrocatechin,  resorcin,  volatile  fatty 
acids.  With  hot  HNO3  they  give  picric  acid,  phthalic  acid,  and  finally 
oxalic  acid  On  distillation  with  reducing  agents,  toluene,  xylene,  methyl- 
anthracene,  etc.,  are  obtained. 

The  chief  constituents  of  the  resins  are  the  resin  esters  (resines),  resin 
acids  (resinoUc  acids,  e.g.,  abietic  acid,  CmHasOj,  and  pimaric  a,cid, 
C20H30O2),  and  indifferent  aromatic  compounds,  resenes,  of  which  little 
is  known.  The  resin  esters  contain  peculiar  alcohols,  the  resin  alcohols 
(p.  526).  These  latter  are  divided  into  the  colorless  resinols  and  the 
colored  resinotannol  ,  which  give  the  reactions  for  the  tannins.  Only  a 
few  resins  contain  resines,  resinolic  acids,  and  resenes  at  the  same  time. 

Hard  resins  are  amorphous,  generally  hard  and  brittle,  containing 
little  or  no  ethereal  oil,  insoluble  in  water,  soluble  m  alcohol,  and  most 
of  them  soluble  in  etiier  and  ethereal  oils.  The  solution  of  many  resins 
in  alcohol  or  turpentine  is  used  as  lacquer  or  varnish.  The  most  common 
hard  resins  are  common  rosin  or  colophony,  gum  benzoin  (contains  ben- 
zoic acid),  gum  dammar,  jalap  resin,  podophyllin,  alces  (also  contain 
aloin,  p.  517),  gum  lac  (purified  shellac),  amber  (also  contains  ethereal 
oils  and  succinic  acid),  gum  guaiac  (contains  also  guaiacic  acid  and  guaiac 
resin  acid),  and  gum  mastic. 

Soft  resins  (balsams)  are  soft  or  semi-fluid  and  are  mixtures  of  ethereal 
oils  and  resin.  They  are  insoluble  in  water,  soluble  in  alcohol  and  ether. 
As  the  ethereal  oil  absorbs  oxygen  the  soft  resins  gradually  become  hard 
in  the  air.  The  most  important  are  balsam  of  copaiba,  turpentine,  pine 
resin,  and  elemi  resin. 

The  true  balsams  (balsam  of  Peru,  p.  501,  balsam  of  Tolu,  p.  501,  storax, 
p.  501)  contain  resin  and  ethereal  oil  only  in  small  amounts  and  consist 
chiefly  of  aromatic  acids,  alcohols,  and  .esters. 

Gum  resins  are  amorphous  mixtures  of  gum,  plant  mucilage,  resin, 
and  ethereal  oils.  They  are  only  partly  soluble  in  water  (the  gum),  and 
in  alcohol  (the  resin).  To  this  group  belong  gum  ammoniacum,  gum 
galbanum,  gum  asafoetida,  gum  gutta,  gum  euphorbium,  gum  olibanum, 
and  gum  myrrha. 

Fossil  resins.  The  most  important  are  amber,  which  consists  chiefly  of 
a  resinol  ester  of  succinic  acid,  and  asphalt,  which  is  produced  by  the 
gradual  oxidation  of  petroleum. 

5.  Cholesterins  or  ChoSesterols 

are  the  monohydric  alcohols  having  the  formula  CjTH^gO,  which  are  very 
widely  distributed  in  the  animal  and  plant  kingdoms,  and  which  were 
first  discovered  in  the  bile  {xo^^r},  bile;  ?rep6o?,  solid).  They  are  dextro- 
or  Isevorotatory  and  seem  to  be  closely  related  to  the  terpenes  or  the 
camphors.  They  form  odorless  and  tasteless  crystals  having  various 
melting-points,  are  insoluble  in  water,  dilute  acids,  and  even  in  concen- 


526  ORGANIC  CHEMISTRY, 

trated  caustic  alkalies;  they  are  very  readily  soluble  in  boiling  alcohol, 
ether,  and  fatty  oils.  If  concentrated  HgSO^  is  added  to  their  solutions 
in  chloroform,  the  chloroform  becomes  purplish-red,  while  the  sulphuric 
acid  has  a  greenish  fluorescence.  If  the  red  chloroform  solution  is  evap- 
orated it  becomes  blue,  then  green,  and  finally  yellow  (Salkowski's  reac- 
tion). The  solution  of  the  cholesterins  in  acetic  anhydride  turns  violet 
and  then  deep  green  when  treated  with  concentrated  sulphuric  acid 
(Liebermann's  reaction). 

Animal  cholesterins,  ordinary  cholesterin,  CjtH^jO,  is  laevorotatory, 
and  occurs  to  a  shght  extent  in  all  fats,  in  blood,  and  nearly  all  animal 
fluids,  in  feces,  but  seldom  in  the  urine,  and  sometimes  m  the  gall-bladcer 
as  round  masses  (gall-stones).  It  is  found  abundantly  in  the  brain,  egg 
yolk,  and  the  nerve  substance.  It  forms  compounds  with  fatty  acids 
which  correspond  to  the  fats  and  which  occur  in  animal  cutaneous  forma- 
tions (hair,  hoofs,  skin,  etc.),  and  to  a  greater  extent  in  wool  fat.  Iso- 
cholesterin  is  also  found  in  wool  fat,  koprosterin,  or  sterconin,  m  normal 
human  feces,  etc. 

Fatty-acid  esters  of  cholesterin  are  prepared  from  wool  fat,  and  when 
pure  the  substances  are  used  as  a  basis  for  salves,  as  they  do  not  become 
rancid  and  because  they  combine  with  considerable  water.  A  mixture 
with  25  per  cent,  water  is  called  lanolin.  Thilanin  is  wool-fat  with 
chemically  combined  sulphur. 

Plant  cholesteiins,  phytosterins,  occur  to  a  less  extent  in  all  plant  fats, 
paracholesterin  in  tan-bark,  caulosterin  in  etiolated  lupin  sprouts,  one- 
cerin,  in  the  Radix  ononidis,  etc.;  betasterin  in  the  sugar-beet  and  sitos- 
terin  in  the  wheat  and  rye  sprouts.  Besides  these  bodies  we  find  a  senes 
of  alcohols  having  a  high  molecular  weight  which  must  also  be  classed 
■with  the  cholesterins  because  of  the  correspondence  of  their  color  reac- 
tion, although  they  differ  in  constitution.  These  bodies  are  cyanchol, 
quebrachol,  cupreol,  lactucerin,  amyrin,  lupeol,  the  resin  alcohols,  etc. 

COMPOUNDS  OF  THE  GLUCOSIDE  GROUP. 

Glucosides^  sometimes  also  incorrectly  called  saccharides  (p.  448), 
are  the  widely  distributed  class  of  compounds  occurring  chiefly  in  the 
plant  kingdom  and  seldom  in  the  animal  world.  On  boiling  with 
dilute  acids  or  alkalies,  sometimes  even  on  boiling  with  water  alone, 
also  by  certain  organized  and  unorganized  ferments,  they  decompose 
into  varieties  of  sugar  and  one  or  more  other,  generally  cyclic, 
compounds.  They  are  to  be  considered  as  ether- like  compounds  of 
the  sugars. 

According  to  the  sugar  split  off  we  differentiate  between  gluco' 
sides,  galactosides,  and  rhamnosides,  etc. 

They  are  colorless  and  odorless  and  not  volatile  without  decom- 
position. They  are  optically  active,  generally  crystallizable,  having 
a  bitter  taste,  soluble  in  water  or  alcohol,  and  with  the  exception  of 
achillein,    amygdalin,    glycyrrhyzin,    indican,    sinigrin,  solanin,   the 


COMPOUNDS  OF  THE  GLUCOSIDE  GROUP.  527 

cerebrosides  and  glycoproteids  are  free  from  nitrogen.  With  the 
exception  of  aehillein,  solanin,  glycoproteids,  which  are  hetero- 
carbocycUc  compounds,  they  are  all  isocarbocyclic  compounds  whose 
exact  constitution  has  not  been  thoroughly  investigated.  Those  of 
known  constitution  have  been  treated  of  in  connection  with  their 
mother-substance. 

Absinthin,  CgoH^oOg,  found  in  the  wormwood;  decomposes  into 
glucose  and  a  resinous  body. 

^sculin,  (C,5Hifl02)2-l-3H20,  in  the  horse-chestnut;  decomposes  into 
glucose  and  a^sculetin,  CgHgO^  (p.  501). 

Apiin,  CgyHsfPig,  occurring  in  the  parsley,  splits  into  glucose  and 
apigenin,  CisHioOg. 

Arbutin,  Ci2H,e07,  with  methyl  arbutin,  in  the  leaves  of  the  Uvse  ursi; 
yields  glucose  and  hydrocfuinone  or  methyl  hydroquinone  on  cleavage. 

Cerebrosides,  CjoHagNgOaa,  and  homologues  of  this  formula,  cerasin, 
cerebrin,  and  encephalin,  split  into  galactose  and  bodies  which  have 
been  little  studied,  but  which  split  into  fatty  acids  and  ammonia.  The 
cerebrosides  are  found  combined  with  lecithin  as  bodies  called  protagons 
in  the  brain  and  nerve  substance. 

Quinovin,  CgoH^gOg,  found  in  cinchona  bark;  splits  into  a  methyl 
pentose,  quinovose,  CgHjaO^,  and  quinovic  acid,  Cg^HasO^. 

Cathartic  acid,  CaoHajNOig,  the  active  principle  of  the  senna  leaves 
(Folia  sennse)  and  of  the  buckthorn  (Cortex  frangulse);  decomposes 
into  glucose  and  cathartogenic  acid,  C24H2(;NO,o. 

Cnicin,  C^gHgeOis,  in  the  leaves  Centaurea  benedicta  (blessed  thistle); 
decomposes  into  hexose,  fatty  acids,  and  phenol  and  aldehyde  compounds. 

Colocynthin,  CseHg^Ogg,  the  active  body  in  the  fruit  of  Citrullus 
colocynthis;   splits  into  glucose  and  colocynthein,  C^^H  640,3. 

Coniferin,  C,eH220s4-2H20,  in  the  asparagus  ana,  in  the  cambium  of 
several  of  the  coniferae;  separates  as  colorless  crystals  on  the  evaporation 
of  the  same.     By  emulsin  it  decomposes  into  glucose  and  coniferyl  alcohol: 

Ci6H2208  +  H20  =  C6Hi206  +  C,oH,203  (p.  494). 

Convolvulin,  Cg^HgeOa:,  the  active  principle  of  jalap  resin  (Resina 
jalapse);  decomposes  into  glucose,  rhodiose  (a  methyl  pentose),  methyl- 
ethyl  acetic  acid,  CgHioOa,  oxylauric  acid,  C12H24O3,  decylenic  acid, 
CioHi^Oa,  and  convolvulinolic  acid,  C,5H3o03. 

Digltilis  glucosidss.  The  dried  leaves  of  Digitalis  purpurea  contain 
the  glucosides  digitonin,  02^11470,4  (cleavable  into  digitogenin,  CgHasOg, 
glucose,  and  galactose),  digitalin,  C,,H,fiO,4  (splits  into  digitahse,  0711,405, 
(ethyl  pentose),  digitaligenin,  C22H30O,,  and  glucose,'  CeHi.Oe),  and 
digitoxm,  0^H,4O„  (which  may  be  split  into  digitoxigenin,  C.2H,,04,  and 
digitoxose,  0511,204).  Commercial  digitalin  consists  of  a  mixture  of  the 
above  three  glucosides.  If  it  is  dissolved  in  concentrated  sulphuric 
acid  and  then  treated  with  a  drop  of  bromine  water  a  violet-red  coloration 
IS  obtamed.  If  the  digitalin  is  dissolved  in  acetic  acid  and  a  trace  of 
FeOl3  added  and  then  an  equal  volume  of  H2SO4,  without  mixing,  an 
intense  red  zone  is  obtained. 

Ericolin,  O26H34O3,  with  arbutin  in  the  leaves  of  Uvae  ursi,  decomposes 
into  2  mols.  ericmol,  CioHigO,  and  glucose. 


528  ORGANIC  CHEMISTRY. 

Frangulin,  C21H20O9,  the  yellow  body  of  the  frangula  bark;  splits  into 
rhamnose  and  emodin  (p.  517). 

Gentiopicrin,  C20H30O12,  of  the  gentian  root;  decomposes  into  glucose 
and  gentiogenin,  Ci^HjeOg. 

Glucotannoids,  see  Tannins  (p.  495). 

Glycyrrhizic  acid,  C^^HggNOig,  is  found  as  ammonium  salt  in  the 
liquorice-root  (Radix  glycyrrhiza?  or  Liquiritia})  and  splits  into  glycyr- 
rhetin,  C32H47NO4,  and  parasaccharic  acid,  CgHioOg. 

Helleborein,  C37H56O18,  in  the  roots  of  the  black  hellebore  (Helleborus 
niger,  etc.);   splits  into  glucose  and  helleboretin,  CigHgoOgjand  acetic  acid. 

Hespiridin,  CgoHeoOgv,  in  the  orange,  lemon,  pomegranate,  and  de- 
composes into  glucose,  rhamnose,  and  hesperitin,  CieHj^Oe  (isoferulic  acid, 
phloroglucin  ester,  p.  50i). 

I.iain,  C24H2eOi3,  in  the  root  of  the  blue  flag  (Rhizoma  iridis);  de- 
composes into  glucose  and  irigenin,  C,^H,60s  (a  polyoxy  ketone). 

jalapin,  Cg^HgeOig,  in  jalap  resin  (Resina  jalapa?);  splits  into  glucose 
and  jalapinolic  acid,  C16H30O3  (oxyhexdecylic  acid). 

Menyanthin,  CggHsoOj^,  in  the  buck-bean;  splits  into  2  mols.  glucose 
and  menyanthol,  C21H34O6. 

Ononin,  CgcHjeO,!,  occurs  with  the  little-known  glucosides  pseudo- 
oninin  and  onon  in  the  Radix  ononidis,  and  splits  into  glucose  and 
formonetin,  CieHj^Og,  which  spUts  further  into  ononetin,  CisllieOg,  and 
formic  acid. 

Phlorhizin,  C22H24O10  +  2H2O,  in  the  cherry-tree,  apple-tree,  pear-tree, 
and  plum-tree,  and  splits  into  glucose  and  phloretin,  C15H14O5,  which  is  the 
phloroglucin  ester  of  p-oxyhydrocoumaric  acid  and  which  splits  further 
mto  phloroglucin  (p.  4S2)  and  phloretic  acid  (p.  502). 

Populin,  benzoylsahcin,  Ci3H,7(C6H5-CO)07  +  2H20,  in  the  silver 
poplar ;  decomposes  into  salicin  (see  below)  and  benzoic  acid. 

Protagons,  see  Cerebrosides  (p.  527). 

Pseudostrophantin,  C4oH6oOje  +  H20,  occurs  in  the  seeds  of  the  Stro- 
phantus hispidus,  and  splits  into  pseudostrophantidin,  CjgH^oOe,  and  a 
.sugar,  C12H22O11. 

Quercitrin,  C2iH220,2  +  2H20,  in  the  bark  of  the  black  oak;  decomposes 
into  quercetin  (p.  M2)  and  rhamnose  (p.  444). 

Ruberythr  c  acid,  C26H2SO14,  in  madder^root,  forms  yellow  shining 
needles  which  split  into  alizarin  and  glucose : 

C,,li,sOu  +  2H2O  ^  C.^H  A  +  2C6H,20fl. 

Salicin,  Cj3H,s07,  in  the  bark  of  the  willow-tree  and  several  varieties 
of  poplars;  is  split  into  glucose  and  saligenin  (p.  491):  C,3H,s07  +  H20  = 
C«H„06  +  C6H4(OH)-CH2-OH.  On  oxidation  it  yields  helicin,  C,3H,807 
(salicyl  aldehyde  glucose),  which  may  also  be  prepared  synthetically. 
Helicin  is  converted  into  salicin  by  nascent  hydrogen. 

Saponins  is  the  name  given  to  a  series  of  compounds  having  the 
formula  CjjH2v_80,„(n=  17  to  26),  which  occur  in  the  ordinary  soap- 
wort  (saponaria  officinalis),  in  the  soap-bark  (Cortex  quillajsp),  in  sarsa- 
parilla-root  (Radix  sarsaparillip)  (in  this  as  smilacin,  also  as  sarsamponin 
and  smilasaponin) ,  and  about  130  other  plants.  They  form  white  amor- 
phous powders  having  a  harsh  taste  and  whose  dust  causes  sneezing  and 
whose  watery  solution,  even  when  diluted  to  1 :  1000,  foams  when  shaken. 


BITTER  PRINCIPLES.  529 

On  boiling  with  dilute  acids  they  split  into  glucose  and  sa'pogenin,  Ci^HggOj. 
The  poisonous  saponins  are  also  called  sapotoxines. 

Scillain,  scillitoxin,  (CeHioOg)^:,  in  the  squill  (Bulbils  scillse) ;  decom- 
poses into  glucose,  butyric  acid,  and  isopropyl  alcohol, 

Xanthorhamnin,  C34H42O20'  rhamnin,  rhamnegin,  in  the  fruits  of  vari- 
ous varieties  of  riiamnus,  and  splits  into  rhamnetin  (p.  542)  and  rhain- 
ninose,  which  can  be  split  into  rhamnose  (p.  444)  and  galactose. 


BITTER    PRINCIPLES 

are  numerous  bodies  which  consist  only  of  C,  H,  and  0,  have  a  bitter 
taste,  and  are  colorless  or  only  faintly  yellow  in  color  and  generally 
markedly  crystalline.  They  occur  ready  formed  in  the  plants  and 
form  the  active  constituent  of  the  same.  Their  behavior  towards  chemi- 
cal agents  is  very  diverse,  and  only  a  few  combine  with  acids  or  bases. 
Most  of  them  are  decomposed  by  these  agents.  Nearly  all  dissolve  with 
difficulty  in  water,  but  dissolve  easily  in  alcohol  and  ether.  Their 
constitution  has  not  been  sufficiently  studied,  but  they  all  seem  to 
belong  to  the  isocarbocylic  compounds.  Those  of  known  constitu- 
tion will  be  discussed  with  their  mother-substances. 

Agaricin,  agaricic  acid,  CieHgoOg  +  HgO,  is  obtained  from  the  resin  of 
the  touchwood  as  a  white  amorphous  or  crystalline  powder  which  melts 
at  140°. 

Angelicin,  hydrocarotin,  CigHgoO,  with  angelic  acid  in  the  roots  of 
Angelica  archangelica ;  also  in  the  carrot. 

Arnicin,  CgoHgoO^,  in  the  arnica-flowers. 

Artemisin,  CigHigO^,  with  santonin  in  the  worm-seed. 

Acorin,  acoretin,  CggHgoOe,  in  the  sweet  flag. 

Bryonin,  C^gHgoOp,  in  the  roots  of  the  bryony  (Bryonia  alba). 

Euphorbon,  C15H24O,  in  euphorbium  resin. 

Erythrocentaurin,  CgHj^Og,  in  the  centaury  herb. 

Hop  bitter,  C25H3e04,  in  the  strobiles  of  Humulus  lupulus  (lupulin). 

Capsaicin,  OgHj^Oa,  is  the  active  principle  of  the  Spanish  pepper  (Fruc- 
tus  capsici). 

Cascarillin,  CiaHi^O^,  in  the  Cortex  cascarillae. 

Colombin,  C21H02O7,  in  the  Radix  Colombo. 

Kosin,  kussin,  C22H2fi07,  in  the  Flores  koso. 

Pimpinellin,  C^fi^2^5,  in  the  Radix  pimpinellae. 

Picrotoxin,  in  the  Cocculus  indicus,  consists  of  a  mixture  of  picro- 
toxinin,  C^^-^^Pq,  and  picrotin,  CgHj^Oy. 

Podophyllotoxin,  0,511,^6 +  2H2O,  in  Podophyllin. 

Quassin,  CgaH^aOio*  i"  quassia- wood  (Lignum  quassiae). 

Urson,  C30H48O3+2H2O,  in  the  leaves  of  the  bearberry  (Folia  Uvse 
ursi). 


530  .   ORGANIC  CHEMISTRY. 


COMPOUNDS  OF  THE    PIGMENT  GROUP. 

All  organic  bodies  having  color  are  not  pigments,  i.e.,  they  do  not 
permanently  color  animal  or  vegetable  fibers.  Only  those  com- 
pounds show  coloring  characteristics  which  are  bases  or  acids,  be- 
cause they  unite  with  the  animal  or  vegetable  fibers  forming  salt-like 
combinations.  Only  certain  of  the  coloring  matters  have  the  power  of 
permanently  dyeing  the  vegetable  fibers  directly  {substantive  dyes), 
while  another  group  (adjective  dyes)  in  order  to  permanently  color 
vegetable  fibers  require  a  fixing  agent,  which  combines  not  only  with 
the  fiber,  but  also  with  the  pigment. 

The  fixing  agents  are  called  mordants  and  the  aluminium,  tin,  and 
ferric  salts  are  especially  suited  for  this  purpose.  The  fibers  are 
dipped  in  these  solutions  and  then  heated  (steamed),  whereby  the  salts 
are  decomposed  and  the  metafile  oxide  or  metallic  hydroxide  pre- 
cipitated in  a  finely  divided  state  in  the  fibers.  The  coloring  matter 
now  forms  with  this  an  insoluble  compound  which  forms  on  the  fiber. 
Proteids  also  serve  as  mordants,  giving  the  plant  fibers  the  character 
of  an  animal  fiber,  also  fats,  fluorine  compounds,  or  tannic  acid  alone, 
or  with  antimony  salts.  Indifferent  pigments  are  those  without  acid 
or  basic  character,  which  dye  only  when  they  are  precipitated  from 
their  soluble  compounds  upon  the  fibers  (indigo)  or  when  they  are 
given  salt  properties  by  converting  them  into  sulphonic  acids  (indigo 
and  many  artificially  prepared  dyes). 

The  pigment  nature  of  a  body  is  dependent  upon  the  presence  of 
certain  atomic  groups  called  the  chromophore  group.  Compounds 
containing  chromophore  groups  are  called  chromogens  and  become 
true  pigments  only  after  the  introduction  of  groups  giving  salt-forming 
(i.e.,  acid  or  basic)  properties  to  the  compound.  Many  bodies  used 
as  dyes  are  colorless  and  only  become  colored  with  the  mordants, 
acids,  or  bases. 

If  the  pigment  compound  produced  on  the  fibers  is  resistant  to 
the  influence  of  the  air,  of  soap-water,  dilute  acids,  and  alkalies,  it  is 
called  fast,  and  if  not  it  is  called  unfast. 

The  coloring  matters  are  destroyed  by  oxidizing  agents,  e.g.,  by 
H2O2  of  the  air  (grass-bleach),  or  by  chlorine  (chlorine-bleach).  By- 
reducing  agents  (HgS,  SO2,  nascent  hydrogen)  the  colors  are  bleached; 
still  generally  no  destruction  of  the  pigment  occurs,  but  colorless  com- 


COMPOUNDS  OF  THE  PIGMENT  GROUP.  531 

pounds  with  hydrogen  are  produced  which  on  oxidation  (often  even 
by  the  air)  yield  the  coloring  matter  again  and  are  called  leuco-com- 
pounds  (p.  503). 

On  shaking  a  solution  of  a  pigment  with  animal  charcoal  this 
latter  removes  most  of  the  coloring  matters.  Most  of  the  solutions 
of  coloring  matters  show  characteristic  absorption  bands  when  viewed 
at  through  a  spectroscope. 

The  artificial  dyes,  often  called  coal-tar  colors  on  account  of  their 
obtainment  from  coal-tar,  have,  because  of  their  beautiful  shades 
and  simphcity  of  use,  nearly  entirely  superseded  the  natural  dyes. 
They  are  nearly  all  of  them  carbocyclic,  nitrogenous  compounds  and 
may  be  divided  into  the  following  groups:  1.  Di-  and  triphenyl- 
methane  colors  (the  last  also  called  aniline  dyes,  p.  505) ;  2.  Azo  dyes 
(p.  510) ;  3.  Nitro  and  nitroso  dyes  (pp.  479,  515) ;  4.  Anthracene  dyes 
(p.  517);  5.  Quinoline  and  acridine  dyes  (p.  540);  6.  Quinonimide 
dyes  (p.  485) ;  7.  Azine,  oxazine,  and  thiazine  dyes  (pp.  543,  544) ;  8. 
Azole  dyes  (p.  552);  9.  Benzopyrone  dyes  (p.  541);  10.  Benzopyrrol 
dyes  (p.  546). 

The  natural  dyes  occur  either  already  formed  (pigments)  or  they 
are  obtained  from  bodies  that  are  colorless. 

The  vegetable  colors  with  the  exception  of  indigo  and  chlorophyll 
are  free  from  nitrogen,  are  isocarbocylic  compounds,  and  may  be 
divided  into  the  following  groups :  1.  Pyrone  derivatives;  2.  Benzo- 
phenone  derivatives;  3.  Flavone  and  xanthone  derivatives;  4. 
Hydrindene  derivatives ;  5.  Orcine  derivatives;  6.  Anthracene  deriva- 
tives;   7.   Colors  of  unknown  constitution. 

The  animal  colors,  with  the  exception  of  the  lipochromes,  which 
are  also  widely  distributed  in  the  vegetable  kingdom,  contain  nitro- 
gen, are  heterocarbocyclic  compounds,  and  are  all  pyrrol  derivatives. 

The  coloring  matters  of  known  constitution  have  been  discussed 
with  their  mother-substances. 

Alkannin  alkanet  red,  C^sHi^O^,  occurs  in  the  alkanet-root. 

Anthocyanin  is  found  in  the  violet  and  corn-fiower. 

Anthoxanthin,  the  pigment  of  fruits  with  bright-red  color  (straw- 
berry, etc.). 

Bixin,  CjgHg^Og,  is  the  red  pigment  of  the  orlean. 

Carthamin,  C^Ji.aO^,  in  the  safflower  (flowers  of  the  Carthamus  tinc- 
torius),  is  a  red  powder  which  is  soluble  in  alkalies  with  a  yellowish-red 
color. 

Curcumin,  CjiHjoOe,  the  coloring  matter  of  turmeric,  forms  orange- 


532  ORGANIC  CHEMISTRY. 

yellow  crystals  which  are  soluble  in  alkalies  with  a  brown-red  color. 
Paper  impregnated  with  turmeric  turns  brown  with  alkalies.  Acids 
reproduce  the  yellow  color;  with  boric  acid  the  paper  turns  orange  red 
on  drying. 

Lipochromes  are  the  yellow  or  red  pigments  of  fatty  tissues,  the 
corpora  lutea,  the  cones  of  the  visual  epithelium  of  birds  and  reptiles 
(called  chromophan  and  cidoro-,  ocantho-,  and  rodophan,  according  to  the 
color),  of  the  yolk  of  the  egg  {luteines) ,  of  corn,  many  stamens,  flowers, 
etc.     Closely  related  by  chemical  and  spectroscopic  behavior  we  haxe  the 

Xanthocarotin,  xanthophyll,  chrysophyll,  which  accompany  chloro- 
phyll and  form  the  yellow  pigment  of  the  leaves  and  many  flowers,  also 

Carotin,  CisH240,  the  coloring  matter  of  the  yellow  carrots  and  many 
other  plants.  It  is  the  chief  constituent  of  the  coloring  matters  of  saffron 
(Crocus),  which  was  formerly  called  polychroit  or  crocin. 

Rottlerin,  CggHgoOg,  kamalin,  mallotoxin,  the  active  constituent  of  the 
kamala,  forms  flesh-colored  crystals  whose  alkaline  solution  is  red  and 
which  dyes  silk. 


III.  HETEROCARBOCYCLIC  COMPOUNDS. 
CONSTITUTION. 

The  heterocarbocyclic  compounds  are  those  compounds  whose 
molecule  contains  a  ring-formed  closed  chain  (an  atomic  ring)  which 
is  composed  of  other  atoms  besides  C  atoms  in  the  ring.  Besides  the 
heterocyclic  compounds  with  one  atomic  ring  we  also  know  of  those 
with  double  or  condensed  atomic  rings  (p.  298). 

All  these  compounds  are  in  behavior  quite  similar  to  the  isocarbo- 

cyclic  compounds,  and  what  has  already  been  given  in  regard  to  these 

compounds  applies  in  general  to  the  heterocarbocyclic  compounds. 

A  complete  separation  of  the  heterocarbocyclic  compounds  from  the 
aliphatic  compounds  is  not  rational,  as  a  great  many  have  out  of  necessity 
been  discussed  in  connection  with  their  aliphatic  mother-substances,  as 
they  can  be  obtained  from  these  and  also  because  they  can  be  transformed 
into  the  aliphatic  compounds.  Of  these  compounds  which  have  already 
been  discussed  with  the  aliphatic  compounds  we  find  the  anhydrides  of 

/Ro- 
many alcohols,  acids,  and  their  derivatives;  eg.,  ethylene  oxide,  <r«fT^>0, 

CH  ""CO  ^ 

succinic    anhydride,     <CH^-CO^^'    lactides,  lactames,  lactones,    e.g., 

butyllactone,  0<'        |        \,  imides,  e.g.,  succinimide,<QTT2_pJ:;  >NH; 

salts  of  polybasic  acids  with  polyvalent  metals;    e.g.,   lead    malonate, 
CH2<pQQ>Pb;     also   the    di-  and   polyamines,    e.g.,    ethylen diamine, 

HN<^gCQ^'>NH;    the   imines,  e.g.,  ethylenimine,   <^^2>nH;    the 

ureids  and  purin  derivatives,  e.g.,  alloxan,  OC<-[sxrT_QQ>CO.  . 

In  the  following  pages  the  heterocarbocycHc  compounds  having 
5  and  6  atoms  in  the  ring  and  having  the  same  bondage  as  the 
atoms  of  the  benzene  ring  will  be  discussed.  These  rings,  in  con- 
tradistinction to  the  rings  with  more  or  less  atoms,  cannot  be 
ruptured  in  a  simple  manner,  but  form  compounds  corresponding  to 
the  benzene  compounds,  from  which  the  derivatives  can  be  derived 
without  a  change  in  the  atomic  rings. 

The  addition  products  of  the  heterocarbocyclic  compounds  will  be 

533 


534  ORGANIC  CHEMISTRY. 

treated  of  in  connection  with  the  individual  members.  These,  like 
the  addition  products  of  the  isocarbocyclic  compounds,  because  of 
their  chemical  behavior  (p.  326),  belong  to  the  ahphatic  compounds. 

Of  the  heterocarbocychc  compounds  those  containing  ""N"  atoms 
in  the  ring,  the  azocarhocyclic  compounds,  are  the  most  important.  No 
element  forms  such  a  large  and  stable  number  of  heterocarbocychc 
compounds  as  nitrogen.  They  may  also  be  considered  as  benzene 
derivatives  in  the  broad  sense,  produced  by  replacing  the  °"CH~ 
groups  of  the  benzene  ring  by  °"N~  atoms. 

TRANSITION  BETWEEN  HETEROCARBOCYCLIC    AND    ISOCARBO- 
CYCLIC AND  ALIPHATIC  COMPOUNDS. 

Although  only  a  few  isocarbocyclic  compounds  can  be  obtained  from 
the  aliphatic  compounds,  nearly  all  heterocarbocyclic  compounds  can 
be  prepared  from  aliphatic  or  isocarbocyclic  compounds,  and  in  fact 
all  those  that  are  of  most  use. 

Alkylpyridines  are  produced  by  heating  aliphatic  aldehyde  ammonia 
alone  or  with  aliphatic  aldehydes  or  ketones,  thus: 

4CH,-CHO  +  NH3=4H,0  +  HC^gH=CH^^^j,_       r^^tJ^^thyU 

Alphylpyridines  are  prepared  by  heating  certain  isocarbocyclic  de- 
rivatives with  hydroxylamine;   e.g., 

CH.<8^::g8=C:H:  +  NH^OH=3H,0  +  HC<gH:C(CA)^N,dj^^^^^^^ 

Alkylate  quinolins  in  the  pyridine  or  benzene  nucleus  are  produced 
from  aliphatic  aldehydes  by  amidobenzene  in  the  presence  of  H2S0^;e.g., 

CeH5-NH2+2CH3-CHO  =2H20  +  2H  +  CeH/  |  ,  methylquinolme. 

\N=^(CH3) 
On  passing  allyl  aniline  over  heated  lead  oxide  we  obtain  quinoline: 

/CH=CH 
CeH5-NH-CH2-GH=CH2=4H  +  C6H,<^   |      ,  quinoline. 

Pyrrole,  furane,  and  thiophene  derivatives  are  produced  from  certain 
aliphatic    diketones;   e.g.,    acetonylacetone,   CH3-CO~CH2~CH2~CO~CH3 

yields  dimethyl  furane,  <CH=C(CH^)  ^^'  ^^  splitting  off  of  H2O,  dimethyl 
thiophene,  <CH=cfeH')  >  ^'  ^'^  distillation  with  PgSg,  and  dimethyl  pyrrole, 
<pS=p^n5^\>NH  on  distillation  with  ammonia.     From  the  aliphatic 

mucic  or  isosaccharic  acid  we  can  obtain  furane  by  dry  distillation,  thio- 
phene on  distillation  with  BaS,  and  pyrrole  derivatives  by  distillation  of 
their  ammonium  salts. 

The  /?-ketonic  acid  esters  (p.  365)  can  also  be  used  in  the  preparation 
of  the  heterocarbocylic  compounds.  On  heating  with  aldehyde  ammonia 
ihey  give  alkyldihydropyridine  carbonic  acid  ester,  e.g., 


HETEROCARBOCYCLIC  COMPOUNDS.  535 

+  CH3-CHO  +  NH3       -^^^^^3''<C(COOC2H5)=C(CH3)>^^  +  2^20» 

with  anilines  they  give  alkyloxyquinoHne : 

/C(CH3)=CH 

\n  ==C(0H) 
with  phenylhydrazin  they  yield  phenylalkylpyrazolones,  e.g., 

CH3-C0-CH,-C00-CA_     C(CH3)=N^^.p  „    ,  „  ^  ,  ^  „  ^ 

Diazindiazole  (purin)  is  obtained  from  uric  acid  (p.  415). 

N~CIT 
Triazine,   CH^^_q^^N,  and    its    derivatives   are    produced    from 

HCN  and  its  derivatives  (p.  385)  by  polymerization. 

Condensed  heterocarbocyclic  compounds  are  obtained  from  the  ortho- 
substitution  products  of  benzene  and  naphthalene  by  splitting  off  of  H^O 
(pp.  483  and  4:^6). 

The  conversion  of  heterocarbocyclic  compounds  into  isocarbocyclic 
or  aliphatic  compounds,  with  the  exception  of  the  addition  products 
and  the  compounds  with  more  or  less  than  5  and  6  atoms  in  the  ring, 
can  only  be  done  with  difficulty.  The  azocyclic  ring  is  generally  more 
resistant  to  rupture  and  more  stable  than  the  benzene  ring. 

'Pyridines  on  heating  with  HI  are  converted  into  paraffines;  e.g., 
pyridine,  C5H5N,  yields  hexane,  CgHj^. 

The  benzene  ring  of  the  quinolines  is  destroyed  on  oxidation,  being 
converted  into  pyridine  carboxylic  acid  (p.  537).  The  pyridine  ring  in 
a-alkylquinolines  is  destroyed  by  KMnO^,  yielding  the  derivatives  of 
o-amidobenzoic  acid: 

r  Tx  /CH=CH  rn  ^P  TT  ^COOH  (Acetyl-o-amido- 

CoHX  I  +50=LU2  +  06il,<j^jj(^(.Q.(.jj^^     benzoic  acid.) 

Pyrrole,  furane,  and  thiophene  derivatives  yield  fumaric  or  maleic  acid 
derivatives  on  oxidation,  e.g., 

<ggl™  >  O  +  30 = HOOC-CH=CH-COOH. 

NOMENCLATURE. 

In  general  the  nomenclature  of  these  compounds  is  the  same  as 
the  isocarbocyclic  compounds.  The  differences  will  be  mentioned  in 
connection  with  the  individual  groups.  The  six-membered  azocyche 
compounds  are  called  azines,  the  five-membered  azoles  (p.  550). 
According  as  in  the  ring  formation,  one,  two,  etc.,  other  atoms  take 
part  besides  C  atoms,  we  designate  them  mono-,  di-,  etc.,  hetero- 
atomic  rings,  and  as  to  the  total  number  of  atoms  forming  the  ring 


536 


ORGANIC  CHEMISTRY. 


we  differentiate  between  three-,  four-,  five-,  etc.,  membered  rings.  The 
compounds  produced  by  condensation  of  iso-  with  heterocarbocycUc 
rings  are  designated  by  adding  the  prefix  benzo-,  phen-,  dibenzo-  or 
diphen-,  naphtho-,  etc.,  to  the  name  of  the  heterocarbocycUc  ring 
(pp.  539,  541,  etc.). 

CLASSIFICATION. 

According  to  the  number  of  atoms  forming  the  ring,  the  follow- 
ing six-  and  five-membered  chief  groups  are  differentiated,  and  these 
divided  into  sub-groups  according  to  the  number  of  the  different 
atoms  (hetero  atoms)  in  the  ring,  so  that  first  the  mono-  and  then  the 
di-,  tri-,  etc.,  hetero-atomic  compounds  will  be  discussed.  The  addition 
products  and  condensed  compounds  will  be  treated  in  connection 
with  these  subgroups. 

The  compounds  of  the  alkaloid  and  protein  groups  which  are 
treated  of  at  the  end  cannot  be  placed  in  any  of  the  foregoing  groups, 
as  their  constitution  has  not  been  sufficiently  studied  to  warrant 
such  arrangement  for  the  present. 


SIX-MEM BERED   COMPOUNDS  WITH  ONE  OTHER  ATOM  IN  THE 


Pyridine,  C5H5N. 

CH 

^  \ 
HC/?   ^'CH 


CARBON  RING. 

Pyrone,  QH.O,. 

CO 

X  \ 
HC       CH 


Penthiophene,  CgHgS. 

CH2 

X  \ 
HC       CH 


HCa      a'CH 

Quinoline,  CeHjN. 
CH      CH 

3CH 


HC;J 

I 
HCa 

\ 

N 


2CH 
CH 


HC       CH 

\o^ 

IsoquinoHne,  C9H7N. 
HC      CH 

HC 

I 

N 

\ 
HC 


\ 
C        CH 

II         I 
C       CH 

CH 


HC       CH 

\^ 

Acridine,  CijHgN. 
CH     CH      CH 


HC 


HC       C 
CH 


C 


\ 
CH 


C       CH 
CH 


(For  the  meaning  of   the    letters  and   numerals   in   the  rings,  see  pp. 

538  and  540.) 


i 


HETEROCARBOCYCLIC  COMPOUNDS.  537 

As  in  these  compounds  the  hydrogen  can  be  replaced  by  alkyls, 
it  follows  that  a  series  of  homologous  compounds  can  be  derived 
therefrom,  e.g.,  C5H4(CH3)N,  C5H3(CH3)2N,  etc.  From  these,  as  in 
the  case  of  the  corresponding  benzene  derivatives,  on  oxidation  of 
the  alkyl  groups  we  obtain  carboxylic  acids;  e.g.,  pyridine  mono-, 
pyridine  di-,  pyridine  tri-,  pyridine  tetracarboxylic  acids  and  pyri- 
dine pentacarboxylic  acid.  The  original  hydrocarbon  can  be  obtained 
from  these  acids  by  the  splitting  off  of  the  carbon  dioxide  groups. 

These  compounds,  like  the  benzene  derivatives,  also  form  addition 
products  whereby  monovalent  atoms  or  radicals  attach  themselves  with 
the  complete  or  partial  rupture  of  the  double  bonds  (p.  463) ;  thus  from 
pyridine  we  obtain  a  hexahydride  derivative,  C5H5NH6,  which  on 
oxidation  again  yields  pyridine.  Tliis  behavior,  which  is  analogous  to 
the  benzene  nucleus,  is  explained  by  its  constitution. 

Pyridine  may  be  considered  as  benzene  in  which  a  trivalent  ^CH~ 
(methine)  group  is  replaced  by  one  ^N~  atom,  while  quinoline  may  be 
derived  from  naphthalene,  and  acridine  from  anthracene,  in  a  similar 
manner. 

In  the  same  way  naphthoquinoline,  C13H9N,  may  be  derived  from 
phenanthrene,  Ci^H^o,  by  replacing  one  ^CH~  group  by  ^N~,  and  also 
anthraquinohne,  CiyHuN,  from  chrysene,  C18H12.  These  compounds 
behave  like  quinoline  bases  and  may  form  corresponding  derivatives. 

The  number  of  isomerides  is  even  greater  than  with  the  benzene 
derivatives,  as  the  position  of  the  replacing  groups  as  compared  to 
the  nitrogen  must  be  considered  (p.  538). 

In  all  these  compounds  the  ""N"  atom  is  combined  to  the  carbon 
by  all  three  valences,  hence  they  may  be  considered  as  tertiary  amines. 
As  would  be  expected  from  this,  they  are  strong  bases,  which,  like 
ammonia,  unite  directly  with  acids,  forming  salts,  and  with  alkyl 
iodides,  forming  analogous  compounds  -with  ammonium  iodide  (p. 
379).  Hydrochlorauric  and  hydrochlorplatinic  acids  give  com- 
pounds which  are  difficultly  soluble  and  which  are  similar  to  the 
corresponding  ammonium  salts. 

Penthiophene,  CsHgS  (p.  536),  is  only  known  in  the  form  of  deriva- 
tives which  behave  like  the  thiophene  derivatives. 

Most  of  the  nitrogenous  plant  bases  called  alkaloids  (p.  552)  are 
hydroderivatives  of  pyridine,  quinoline,  and  isoquinoline. 


538  ORGANIC  CHEMISTRY, 


I.  Pyridine  Compounds. 

Pyridine,    CgHgN   (structure,  p.  536). 
Picoline,     CeHyN  (methylpyridine,  isomeric  with  aniline). 
Lutidine,     C7H9N  (dimethylpyridine,  isomeric  with  toluidine). 
Collidine,     CgHuN   (trimethylpyridine,  isomeric  with  xylidine). 
Parvoline,  C^HjaN   (tetramethylpyridine,  isomeric  with  cumidine). 

These  pyridine  bases  occur  with  quinohne  bases  and  their  isomers, 
the  anihnes,  in  coal-tar  and  in  bone  oil  (see  below).  They  are  formed 
on  the  decomposition  of  many  alkaloids  and  by  heating  aliphatic  alde- 
hydes with  ammonia: 

4C2H4O+  NH3  =  C5H2(CH3)3N+ 4H2O. 

They  form  colorless  poisonous  liquids  which  are  volatile  without 
decomposition  and  which  have  a  characteristic  odor.  The  lower 
members  are  readily  soluble  in  water,  while  the  higher  members  are 
not.  The  homologues  of  pyridine  are  readily  oxidized  into  pyridine 
carboxyhc.  acids  (p.  537),  while  pyridine  itself  is  not  attacked  by 
nitric  acid,  iodine,  or  oxidizing  agents,  and  by  sulphuric  acid  only  on 
raising  the  temperature. 

The  hexahydropyridines,  C5H5N(H6),  are  called  piperidines,  methyl 
piperidines  are  called  pipecolines,  the  dimethyl  piperidines,  lupetidines,  and 
the  trimethyl  piperidines,  copelidines,  etc. 

Isomerides.  ihree  mono  derivatives  are  possible,  which  are  desig- 
nated a-,  /9-,  /--pyridines,  according  as  the  substitution  takes  place  near  or 
remote  from  the  N  atom.  Six  biderivatives  are  possible,  which  are  desig- 
nated aa^-,  a/?-,  ay-,  a/?'-,  ^f-,  /S.^J'-pyridines.  Ten  biderivatives  with  two 
different  substitutions  are  possible  (p.  467). 

If  the  attachment  takes  place  at  the  N  atom  due  to  a  rupture  of  the 
double  bond  the  compound  is  called  n-pyridine. 

The  constitution  of  pyridine  is  derived  from  its  formation  from  quinoline. 
This  last  yields  a  pyridine  carboxlyic  acid  on  oxidation,  when  one  benzene 
nucleus  is  destroyed,  similar  to  the  oxidation  of  naphthalene  (p.  514). 
Pyridine  can  be  obtained  from  this  pyridine  carboxylic  acid  by  splitting  off 
2  mols.  carbon  dioxide  (p.  537). 

Bone  oil,  animal  oil  (Dippel's  oil),  is  prepared  from  the  crude  animal 
oil  obtained  in  the  dry  distillation  of  bones  and  other  animal  substances 
by  rectification.     It  contains  chiefly  pyridine  bases,  also  quinoline  bases, 

Eyrrole  and  its  homologues  (p.  544  ,  nitriles  of  the  fatty  acids  and  benzene 
ydrocarbons. 

Dipyridyl,  NH^C^-CsH^N,  corresponding  to  diphenyl  (p.  504);  we  have 
several  isomers  which  on  oxidation  yield  nicotinic  acids. 

Oxy  pyridines,  C5H4(OH)N,  correspond  to  the  phenols  and  give  a 
yellow  or  red  coloration  with  ferric  chloride  or  they  correspond  to  the 


QUI  NO  LINE  COMPOUNDS.  539 

ketones  and  are  then  called  pyridones,  e.g.,  HN<qj£=q^>CO,  r-dioxy- 

pyridone. 

Nicotinic  acid,  C5H^(C00H)N,  /^-pyridine  carboxlyic  acid,  is  produced 
by  the  oxidation  of  nicotine  (p.  5  J4)  and  by  heating  trigonelline  (p.  553) 
with  HCl. 

Cinchomeronic  acid,  C5H3(COOH)2N,  one  of  the  six  known  pyridine 
carboxylic  acids,  is  produced  by  the  oxidation  of  quinine,  cinchonine, 
and  cinchonidine  (p.  555). 

Piperidine,  C5H10NH  or  H2C<^^2~CH2^-^jj^  hexahydropyridine  (p. 

537),  is  produced  by  the  action  of  nascent  hydrogen  upon  pyridine.  It 
is  a  colorless,  alkaline  liquid  having  a  pepper-like  odor.  It  may  also  be 
prepared  from  the  alkaloid  piperine  (p.  553)  by  boiling  it  with  alkaUes. 
Piperidine  is  the  mother-substance  of  the  alkaloids  of  coca  and  most 
of  the  solanum  alkaloids  (p.  557). 

Propyloiperidine,  CgHgCCgHy)!!^!!,  is  produced  by  the  action  of  nascent 
H  upon  allyl  pyridine,  and  is  an  inactive  substance  which  can  be  split 
into  a  laevo  and  a  dextro  modification.  This  latter  is  the  substance  called 
coniine  (p.  554). 

Eucain  B,  C5H8(CH3)3(-0-CeH5-CO)-NH-HCl,  the  hydrochloride  of 
benzoyltrimethyl  oxypiperidine  (also  called  benzoylvinyldiacetonalka- 
mine),  is  used  as  a  local  anaesthetic  instead  of  cocain. 

Euphthalmin,  C5H6(CH3)3(-OC6H5-CHOHCO)-N(CH3)HCl,  the  hydro- 
chloride of  phenyl  glycolyl-n-mcthyl-trimethyl  oxypiperidine  (phenyl  gly- 
colyl=mandelic  acid  radical,  p.  498),  dilates  the  pupils  and  is  used  m 
medicine  instead  of  atropine. 

2.  Quinoline  Compounds. 

Quinoline,       C9H7N  (structure,  p.  536). 
Isoquinoline,  CgHyN  (structure,  p.  536). 
Quinaldine,     C10H9N  (a-methyl  quinoline). 
Lepidine,         C^oHgN  (^--methyl  quinoline). 
Cryptidine,     CnHuN  (dimethylquinoline). 

These  quinoline  or  benzopyridine  bases  occur  with  the  pyridine 
bases  in  bone  oil  (p.  538)  and  in  coal-tar  and  are  prepared  from  many 
alkaloids  (p.  543)  by  distillation  with  caustic  alkalies  (preparation, 
p.  540). 

They  are  liquids  having  peculiar  odors  and  soluble  with  difficulty 
in  water.  Oxidizing  agents,  iodine  and  nitric  acid  only  act  upon 
the  benzene  nucleus  and  not  upon  the  pyridine  nucleus.  By  rupture 
of  the  double  bonds  in  quinoline  up  to  ten  H  atoms  can  be  attached, 
producing  the  hydroquinolines,  e.g.,  C9H7N(Hn,),  decahydroquinoline. 

Two  isomerides  of  quinoline  are  possible  and  are  also  known,  according 
as  the  N  atom  exists  beside  one  of  the  hydrogen-free  C  atoms  or  removed 


540  ORGANIC  CHEMISTRY. 

therefrom  (p.  538).  Seven  isomers  of  monoquinoline  derivatives  are  also 
possible.  The  substituted  H  atoms  in  the  benzene  ring  are  designated 
by  1,2,  3,  4,  or  o-,  in-,  p-,  a-  (ana),  while  in  the  pyridine  ring  they  are 
designated  by  a-,  ,5-,  y-  (p.  538). 

The  constitution  of  the  quinolines  has  been  determined  by  numerous 
syntheses  and  also  by  its  analogous  beha\ior  to  naphthalene  on  oxidation 
(p.  537),  when  it  yields  pyridine  carboxylic  acid,  C5ii3(COOH)2N. 

It  is  produced,  for  example,  by  passing  allylaniline  over  heated  lead 
oxide  (analogous  to  the  preparation  of  naphthalene  from  phenyl  butylene, 
p.  514), 

/CH=CH 
CeHrNH-CH^-Cf  1=CH2  +  0^=  Cetl/  |      +  2H2O; 

\n==ch 

also  from  orthoamidocinnamic  aldehyde  by  splitting  off  water, 
/CH=CH-CHO  /CH=CH 

\NH2  \N— CH 

as  well  as  by  heating  aniline,  glycerin ,  and  sulphuric  acid  with  nitrobenzene, 
which  later  acts  oxidizingly  (Skraup's  synthesis) : 

/H  /CH2OH  /CH=CH 

CflH/         +HOHC<  +0=CeH/  I     +4H2O. 


-NH 


\:^H,OH  '    '  \N— CH 


If  instead  of  aniline  we  use  its  homologues,  we  obtain  the  homologous 
quinolines,  while  if  the  halogen,  nitro-,  etc.,  substituted  amines  are  used 
we  obtain  the  halogen,  nitro-,  etc.,  substituted  quinolines. 

a-Oxyquinoline,  C9H6(OH)N,  carbostyril,  forms  asbestos-like  crystals, 
lodochloroxyquinoline,  called  vioform,  is  used  as  an  odorless  substitute 
for  iodoform. 

Kynurenic  acid,  C9H5(OH)(COOH)N,  an  oxyquinoline  carboxylic  acid, 
occurs  in  dogs'  urine  and  forms  colorless  crystals  which  on  fusion  yield 
T'-oxyquinoline  or  kynurine,  C9H6(OH)N. 

lodoxyquinoline  sulphonic  acid,  loretin,  C9HJ(OH)(S03'H)N,  forms  a 
yellow,  crystalline  powder  which  is  insoluble  in  water. 

Berberine,  papaverine,  narcotlne,  narceine,  hydrast"ne  (see  Alkaloids) 
are  complicated  isoquinoline  derivatives. 

Quinine,  quinidine,  clnchonine,  cinchonidine,  strychnine,  brucine, 
cephaeline,  aconitine  (see  Alkaloids)  are  quinoline  derivatives. 

Quinoline  dyes.  By  the  introduction  of  amido,  alphvl,  and  alkyl 
groups  into  quinoline  we  obtain  various  dyes  which  are  called  quinoline 
red,  quinoline  yellow,  flavaniline,  and  the  cyamines. 

3.  Acridine  Compounds. 

Acridine,  CigHoN  (structure,  p.  r36),  occurs  in  coal-tar  and  forms 
colorless  needles  which  cause  an  active  itching  of  the  skin  and  melt 
at  100°.  The  solution  of  its  salts  have  a  beautiful  greenish-blue  fluores- 
cence. Acridine  and  its  homologues  are  weaker  bases  than  the  quinoline 
and  pyridine  bases.  It  forms  the  mother-substance  of  certain  dyes, 
such  as  chrysaniline  or  phosphin,  acridine  yeUow,  etc. 


PYRONE  COMPOUNDS.  541 


4.  Pyrone  Compounds. 

a-Pyrone,  coumalin,  C5HP2  o^  0<qjj=CH'^^^'  ^®  ^  colorless,  neu- 
tral liquid,  boiling  at  209°,  and  having  an  odor  similar  to  caraway  seeds. 
It  is  produced  by  heating  coumalic  acid  (see  below). 

;-- Pyrone,  pyrocomane,    0<pr7=pTr>C0,    forms    colorless,    neutral 

crystals  which  melt  at  32°.  The  pyrones  and  their  derivatives  on  warming 
with  NH3  are  converted  into  pyridones  (p.  539),  when  the  oxygen  of  the 
ring  is  replaced  by  =NH.  The  properties  of  many  pyrones  is  peculiar, 
especially  dimethyl  pyrone,  05^12(0113)202,  which  although  it  has  a  neu- 
tral reaction,  forms  salts  with  acids  directly  by  addition,  similar  to  am- 
monia. In  these  salts  for  every  hydrogen  atom  of  the  acid  one  molecule 
of  the  pyrone  compound  takes  its  place.  On  account  of  their  analogy 
to  the  ammonium  salts  (pp.  150  and  210)  these  salts  are  called  oxonium 
salts  and  we  must  admit  that  the  formation  of  salts  is  caused  by  the 

TT  pTJ=ptT 

oxygen  in  the  ring  being  tetravalent;  thus,  Q>^^<njj=n^>CO,  di- 
methyl pyrone  hydrochloride. 

According  to  more  recent  researches  numerous  other  cyclic  and  ali- 
phatic compounds  containing  oxygen  have  the  property  of  forming 
salts  such  as  the  oxonium  salts. 

The  same  property  has  been  known  for  a  long  time  in  certain  sulphur 
compounds,  the  sulphonium  or  sulphin  hydroxides  (p.  352),  where  the 
sulphur  atom  appears  tetravalent. 

Comanic  acid  and  coumalic  acid,  both  C5H,(COOH)02,  are  pyrone- 
carbo:;yUc  acids.  The  first  is  produced  from  chelidonic  acid  (see  Below) 
and  the  other  from  malic  acid  by  heating  with  concentrated  sulphuric 
acid. 

Chelidonic  acid,  C5H2(0OOH)2O2,  pyrone-dicarboxlic  acid,  occurs 
in  the  CheUdonium  majus,  and  yields  on  heating  comanic  acid  and  then 
^'-pyrone. 

Moconic  acic,  05H(OH)  (0OOH)2O2,  oxypyrone-dicarboxylic  acid,  occurs 
in  opium,  and  on  boiling  with  water  it  splits  off  OO2  and  is  converted  mto 

Comcnlc  acid,  oxypyrone-carboxylic  acid,  C5H2(OH)(COOH)02;  this 
splits  off  more  OOo  on  heating  and  yields 

Pyromeconic  acid,  /?-oxy-r- pyrone,  C6H3(OH)02. 


/CH=OH 


a-Benzopyrone,   CoH/  |     .     Coumarin  (p.  501)    is   to   be   con- 

\0— 0 
sidered  as  a-benzopyrone. 

Xanthone,  C^^llfi^,  diphenylenkentone  oxide,  is  the  mother  sub- 
stance of  euxanthon,  CigHgO^,  and  of  euxanthic  acid,  CmH,yOii,  both 
occurring  in  Indian  yellow  (p.  440),  and  also  of  the  yellow  plant  pig- 
ment gentisin,  C^Ji.o^^,  of  the  renfan  root  and  daiiscetin,  Oi^HigOo;  also 
of  rhamnochrysine,  OigH^jO;,  and  rhamnocitrine,  C13H10O5  (see  below). 

Flavone,  Ci^HioOj,  is  the  mother-substance  of  numerous  yellow  plant 
pigments,  for  example,  quercetin,  C^^R,o^.j,  from  the  glucoside  quercitnn; 
/jse^in.CisHioOe,  in  the  fustic  wood;  chry sine,  C,,R,^>0^,  in  the  buds  of  the 
various  poplars;  luteoHn,  Ci^HioOe,  in  Reseda  luteola  and  digitahs  leaves; 
galangin,  CisHioOg,  and  campferid,  CijIIigOe,  in  the  galanga  root;   moririt 


542  ORGANIC  CHEMISTRY. 

CijHioOx,  and  maclurin,  Q^^^^O^,  in  fustic;  rhamnetin  (methyl  quercetin)^ 
CuHigO,,  in  the  glucoside  xanthorhamnin;  rhamnazin  (methyl  rhamnetin), 
CiyH^^O,;  and  rhamnolutin,  CigrijoOj,  in  the  buckthorn;  apigenin,  C15H10O5, 
in  the  glucoside  apiin;  scoparine,  Ci4Hio05,  in  the  broom,  and  gossy- 
petine,  CuHigOa,  in  the  cotton  flower. 


HC     CO  CH 

h/VY\h 
Hc!    a    1    ta 

HC      CO 
HC      C     CH 

H(!      C     C-C,Hs 

YY 

Dibenzopyrone            and        Phenylbenzopyrone 
or  Xanthone                                   or  Flavone. 

The  following  pigments  belong  to  the  complex  flavone  derivatives 
but  their  structure  has  not  been  well-studied: 

Santalin,  C15H14O5,  contained  in  the  sandalwood. 

Brasilin,  CigHi^Og,  in  the  Brazil  wood;  forms  yellow  crystals  which  turn 
carmine-red  with  traces  of  caustic  alkalies  or  ammonia  being  oxidized 
to  brasilein,  CjgH  jOg. 

Haematoxylin,  CipHj^Og,  of  the  logwood;  forms  pale-yellow  prisms 
which  are  soluble  with  a  purple  color  in  ammonia  and  caustic  alkalies 
(delicate  reagent  for  these),  being  oxidized  to  hcematein,  CieHijOj. 

SIX-MEMBERED  COMPOUNDS  WITH  SEVERAL  OTHER  ATOMS  IN 
THE  CARBON  RING. 

The  most  important  compounds  belonging  to  this  six-membered 
ring  are  those  containing  nitrogen  and  which  are  derived  from  pyridine, 
quinoline,  and  acridine,  when  =N-  atoms  take  the  place  of  =CH-  groups! 
They  are  called  azines,  and  the  number  of  N  atoms  is  indicated  by  the 
prefixes  di-,  tri-,  tetrazines;  oxazines  contain  one  N  and  one  O  atom, 
thiazines  one  N  and  one  S  in  the  ring,  etc. 

According  as  the  N  atoms  occupy  the  o-,  m-,  or  p-position  relative 
to  each  other  we  designate  them  oiazines,  miazines,  and  piazines. 

I.  Azine  Compounds. 

Orthodiazine,  C^H^N^  or  HC<^jj_(^g>N,  pyridazine,  is  a  liquid 
smelling  like  pyridine  and  boiling  at  208°. 

Metadiazine,  C^H^N^  or  HC^(.jj_(.jj;^N,  pyrimidine,  forms  a  solid 
melting  at  22°  and  having  a  narcotic  odor. 

Dioxyhydrometadiazine,  HC^(^jj_^q>NH,  uracil,  is  closely  related 
to  the  purin  derivatives  (p.  415).     Methyl  uracil  is  thymin  (p.  565). 

Paradiazine,  C^H^Na  or  N^^jj.^^jji^N,  pyrazine,  aldine,  forms  crys- 
als  which  melt  at  55°  and  having  an  onion-like  odor. 


AZINE  COMPOUNDS. 


543 


pTT    — pTJ 

Piperazine,  C^HjoNj  or  HN<^|j2_^g2>^Tjj^  diethylendiamine,   is  a 

hexahydropyrazine.  It  is  obtained  from  ethylene  bromide  by  the  action 
of  ethylendiamine,  and  forms  crystals  which  are  soluble  in  water  and 
melt  at  106°  and  which  dissolve  large  quantities  of  uric  acid.  Spermine 
crystals  (Schreiner's  crystals),  found  in  semen,  seem  to  be  closely  re- 
lated to  piperazine. 

Benzometa- 
diazine,  CgHgNa, 

Cinnoline.  Quinazoline. 

HC     CH  HC      CH 


Benzortho- 
diazine,  CoHeNg, 


Benzopara- 
diazine,  CoHeNj, 

Quinoxaline. 

HC     N 


HC     C     N 

Hi   il  L 


Phthalazine, 
C«HeN,. 

HC      CH 
HC     C     N 

Hi      I     L 

HC      CH 

The  first  three  of  these  four  isomers  are  derived  from  quinoline  and  the 
last  from  isoquinoline,  where  one  =CH-  group  is  replaced  by  =N"-.  Quin- 
azoline is  only  known  in  the  form  of  derivatives,  while  the  others  form 
crystals  having  strong  basic  properties. 

Phenyldihydroquinazoline,  CgHsCCeHa)  NgCHg) .  Its  compound  with  HCl 
is  used  in  medicine  under  the  name  orexin. 

Dibenzoparadiazine,  phenazine,  CjoHgN^,  is  derived  from  acridine,  where 


HC   C  CH 

Hi   I!  A 
HC  N 


HC   N 


^ 


HC   C   CH 

Hi    ij    tn 

HC   N 


CH  N   CH 
HC   C   C  CH 


Hi    I 


DH  N   CH 


(true    blue) ,    mgrosmes 
(indoin   blue,   mauvein, 
toluylene  red,  toluylene 
HON      CH  CH 

HC      C      C     C     CH 
CHN      CH  CH 


one  =CH-  group  is  replaced  by  =N-.  It  is  found 
in  coal-tar  and  forms  yellow  needles  and  by  the  in- 
troduction of  amido-,  alkyl-,  or  alphyl  groups  forms 
the    dyes    called    indolines    "  '  ^     - 

(aniline   black),    safranines 
magdala  red,  indazin  blue), 
CH  N      CH        blue,  Janus  green. 
Tribenzoparadiazine,  naphthophenazine, 

CioHjoN^,  obtained  from  certain  azo  com- 
pounds, forms  colorless  crystals  and  by  the  in- 
troduction of  amido-,  alphyl-,  or  alkyl  groups 
forms  the  dyes  called  eurhodoles,  eurhodines, 
rosindulines  (azocarmin). 

s-Triazine,   HC^xt_qtt>N,   C3H3N3,   cyanidine,   corresponds  to   tri- 

hydrocyanic  acid  and  is  the  mother-substance  of  the  cyanuric  compounds 
(p.  382). 

a-Triazine,  HC<:^jj_^>N,  as  well  as 

v-Triazine,  HC^Qjj_^^N,  is  only  known  in  the  form  of  derivatives. 

In  regard  to  the  meaning  of  s-,  a-,  v-,  see  page  469. 

Phentriazine,  C7H5N3,  is  produced  from  quinoline, 
CgHyN,  by  replacing  two  =CH-  groups  by  two  =N-  atoms. 
It  forms  yellow  crystals  which  melt  at  75°  and  have  a  nar- 
cotic odor. 

Tetrazine,   HC^qjj_-^>N,  as   well   as  its  isomers  is 

not  known  free,  but  the  derivatives  are  known. 


HC      CH 

^\y\ 

HC     C     N 

Hi     l-k 

hW 

544  ORGANIC  CHEMISTRY. 


2.  Oxazine  and  Thiazine  Compounds. 

pTT__  pTT 

Oxazine,  0<rirT^nij>^^H,  is  not  known  free. 

Tetrahydo-paraoxazine,  0<qt^2^  2->]sfjj^  morpholin,  is  a  color- 
less, basic  fluid,  boiling  at  129°  and  which  has  great  similarity  to  piperidine 
(p.  530).  It  is  the  mother-substance  of  the  alkaloids  morphine,  codeine, 
and  thebaine  (see  Alkaloids). 

Phenoxazine,   C6H4<  q   >C6H^,  forms   colorless  leaves  and   by   the 

introduction  of  alkylamine  groups  it  forms  the  oxazine  and  oxazone  dyes 
(Nile  blue  and  gallocyanin),  the  blue  muscarin  pigment. 

N  H 
Phenthiazine,   thiodiphenylamine,    CgH4<    g  >C6H^,  is  produced  from 

diphenylamine  by  heating  it  with  sulphur  and  forms  yellow  scales.  By 
the  introduction  of  alkyl  or  amido  groups  it  forms  the  thionin  dyes,  for 
example,  Lauth's  violet,  methylene  blue,  methylene  green,  thiazine  rei, 
and  thiazine  brown,  thionin  blue  and  toluidine  blue. 

FIVE-MEMBERED  COMPOUNDS  WITH  ONE  OTHER  ATOM  IN  THE 
CARBON  RING. 

These  contain  the  tetrol  group,  C4H4,  which  with  ~NH~,  ~0~,  or 
~S~  form  a  closed  chain: 

Pyrrol,  C4H5N.  Furane,  C4H4O.        Thiophene,  C4H4S. 

HC CH  HC — CH  HC — CH 

II       II  II       II  II       II 

HC      CH  HC      CH  HC      CH 

\/  \/  \/ 

NH  O  S 

The  preparation  and  properties  of  the  derivatives  of  these  com- 
pounds are  the  same  as  the  corresponding  benzene  derivatives. 

I.  Pyrrol  Compounds. 

Pyrrol,  C^HgN,  occurs  in  coal-tar  and  in  bone-oil,  is  produced  by 
heating  succinimide  with  zinc  dust  and  water: 

<CH:= C0>NH  +  4H=  <gH-CH^j^jj^2jj^C. 

Succinimide.  Pyrrol. 

It  16  a  colorless  basic  liquid  boiling  at  130°  and  having  an  odor  similar  to 
chloroform  and  chemical  properties  similar  to  pyridine.  Its  vapors  color 
a  pine  shaving  moistened  with  HCl  purple-red. 


PYRROL  COMPOUNDS.  545 

If  in  pyrrol  the  hydrogen  attached  to  a  carbon  atom  or  to  a  nitrogen 
atom  be  replaced  by  alkyls,  we  obtain  the  homologues  of  pyrrol,  the  pyrrol 
bases,  which  are  also  fomid  in  bone-oil  and  are  faintly  basic  liquids;  e.g., 
methyl  pyrrol,  C.H  =N-CH3,  homopyrrol,  C,H3(CH3)=NH,  ethylpyrrol, 
C,H4=N-C2H5,  dimethylpyrrol,  C^H^CCHg)  =NH. 

Tetraiodopyrrol,  iodol,  C^I^NH,  forms  a  yellow  powder  which  is  used 
as  an  antiseptic. 

Pyrroline,  dihydropyrrol,  C^H^N  or  <^Ich'>  ^^'  ^^^ 

Pyrrolidine,  C^HgN,  or  <CH^-CH^^''^^'  tetrahydropyrrol,  are  pro- 
duced by  the  addition  of  hydrogen  to  pyrrol.  Pyrrolidine  is  the  mother- 
substance  of  most  of  the  coca  and  sclanum  alkaloids. 

Pyrrolidine  carbonic  acid,  C^H8(C00H)N,  is  a  cleavage  product  of  the 
protein  bodies. 

Chlorophyll,  the  pigment  of  the  green  parts  of  plants,  consists  of  C,  H,  O, 
N,  P,  perhaps  also  iron,  and  up  to  the  present  time  is  obtained  more  or  less 
decomposed  as  soft  masses  which  are  soluble  with  a  bluish-green  color  in 
alcohol,  ether,  fatty  and  ethereal  oils.  It  is  decomposed  by  acids  to 
phylloxanthin  and  then  from  this  into  phyllocyanin,  which  on  heating 
with  alkalies  yields  phylloporphyrin,  CmHjgNgO,  and  this,  like  the  hsemato- 

Eorphyrin  obtained  from  haemoglobin,  is  reducible  to  haemopyrrol  (iso- 
utyl  pyrroD. 

Blood-pigments.  The  color  of  the  blood  is  produced  by  the  chromo- 
proteids  oxyhsemoglobin  and  haemoglobin,  which  are  compounds  of  the 
colorless  proteid  globin  with  the  pigments  ha^matin  or  hsemochromogen. 
Closely  related  to  these  are  the  pigments  of  the  bird's-egg  shells,  the  blue 
oocyanin,  the  reddish  oorhodin,  the  green  oochlorin,  and  the  yellow  ooxan- 
thin. 

Hcematin,  Cg^Hg^N-FeOg,  the  cleavage  product  of  oxyhsemoglobin 
(p.  565),  is  a  bluish-black  amorphous  powder  soluble  with  a  red  color  in 
acidified  alcohol,  and  on  oxidation  yields  two  bibasic  himatinic  acids, 
CgHioOg.  On  treatment  with  concentrated  sulphuric  acid  or  hydrochloric 
acid  it  is  converted  into  hamatoporphyrin  (see  below).  Hsematin  gives  a 
characteristic  absorption  spectrum  (p.  45). 

Hcemin,  C.^^tlsJ^^FeO^•RC\,  hsematin  hydrochloride,  Teichmann's 
blood-crystals,  serve  in  the  detection  of  small  amounts  of  blood.  The 
object  containing  the  blood  is  extracted  with  a  little  cold  water  and  this 
extract  allowed  to  evaporate  on  a  glass  slide  and  warmed  with  a  trace  of 
salt  and  a  few  drops  of  glacial  acetic  acid.  On  cooling,  the  characteristic 
bluish-black  rhombic  crystals  of  hsemin  are  seen  under  the  microscope. 

Hcemochromogen,  C64H7oFe2N,o07,  the  cleavage  product  of  haemoglobin 
(p.  566),  forms  dark  crystals  which  are  soluble  in  alkalies  yielding  a  red 
solution,  and  then  quickly  absorb  oxygen,  forming  haematin.  In  acid 
solution  hsematoporphyrin  is  produced.  It  also  gives  a  characteristic 
absorption  spectrum. 

Hcematoporphyrin,  Cj^HgeN^Oe,  the  cleavage  product  of  haematin  and 
hsemochromogen  (which  see)  and  also  often  found  in  the  urine,  forms 
a  brown  amorphous  powder  soluble  with  a  red  color  in  dilute  acids  and 
gives  a  characteristic  absorption  spectrum.  On  oxidation  it  yields  the 
bibasic  biliverdic  acid,  CgHgNO^,  and  on  reduction  it  yields  like  phyllo- 
porphyrin (the  cleavage  product  of  chlorophyll)  and  hajmopyrrol  (isobutyl 
pyrrol). 


546  ORGANIC  CHEMISTRY. 

Melanins  are  the  several  nitrogenous  and  often  ferruginous  pigments, 
closely  related  to  the  blood-pigments,  which  are  found  in  the  skin  of  the 
negro,  in  the  choroidea  and  iris,  in  the  hair,  in  the  urine  and  blood  in  cer- 
tain diseases.  They  are  amorphous  black  or  brown  pigments  which  are 
insoluble  in  water,  alcohol,  ether,  chloroform,  dilute  acids,  but  are  solu- 
ble in  caustic  and  carbonated  alkalies  and  give  an  imperfect  absorp- 
tion spectrum. 

Bile-pigments.  The  color  of  the  bile  is  due  to  hilirubin  and  hiliverdin, 
derivatives  of  the  blood-pigment.  In  gall-stones  we  find  other  pigments 
which  have  been  little  studied,  especially  c/wZeie^m,  CigHigNaOg,  hiliprasin, 
CioHgaNgOe,  bilifuscin,  CigHaoNgO^,  bilicyanin,  and  hilihumin.  These  pig- 
ments are  weak  acids,  insoluble  in  water,  produce  no  absorption  spec- 
trum, and  give  Gmelin's  test:  Float  the  liquid  to  be  tested  upon  nitric 
acid  containing  some  nitrous  acid,  when  at  the  point  of  contact  of  the 
two  liquids  a  series  of  colored  rings  will  be  formed  from  below  upward 
in  the  following  order:  a  yellowish-red  (choletelin),  then  red,  violet-blue 
(bilicyanin),  and  on  top  a  green  ring  (biliverdin) . 

Bilirubin,  CicHigNgOg,  an  isomer  of  hsematoporphyrin  (p.  545),  also 
occurs  in  gall-stones,  in  all  blood  exudates,  in  icteric  urine,  and  in  the 
contents  of  the  small  intestine.  It  forms  dark-red  crystals,  readily  solu- 
ble in  chloroform,  but  difficultly  soluble  in  alcohol.  The  yellowish-red 
solution  is  converted  into  biliverdin  in  the  air.  Nascent  hydrogen  (in 
the  presence  of  water)  converts  bilirubin  as  well  as  biliverdin  into  color- 
less 

Hydrohilirubin,  C32H40N4O7,  which  is  also  found  in  the  intestine. 

Biliverdin,  Ci6H,gN204>  forms  green  crystals  insoluble  in  chloroform 
and  soluble  with  difficulty  in  alcohol. 

Urobilin,  C32H40N4O7,  is  chemically  closely  related  to  bilirubin,  and 
occurs  as  traces  in  normal  urine  and  in  larger  amounts  in  icterus.  It 
forms  an  amorphous  brown  mass  soluble  in  alcohol  or  chloroform. 
Sodiiun  amalgam  converts  it  into  colorless  urobilinogen. 

2.  Benzopyrrol  Compounds. 

The  indol  or  benzopyrrol  compounds  contain  on  one  side  a  benzene 
nucleus  and  on  the  other  side  a  closed  chain,  such  as  is  also  contained  in 
pyrrol,  C4H5N,  consisting  of  four  carbon  atoms  (of  which  two  belong  to 
the  benzene  nucleus)  and  one  nitrogen  atom  (p.  544).  We  can  therefore 
consider  the  indol  compounds  also  as  being  the  substitution  of  =CH2  by 
=NH  in  indene,  C^Hg   (p.  513). 

By  rupturing  the  pyrrol  ring  (oxidation,  etc.)  the  indol  bodies  are 
converted  into  ortho  derivatives  of  benzoic  acid: 

Indol,  CgH^N.  Indoxyl,  CgH^NO.  Isatm,  CgH^NO^. 

CH  CH  CH 

/x  ^\  ^\ 

HC  C— CH     HC  C— C(OH)      HC  C" CO 
hA  Uh     hU  L  Hi  I     i(OH) 

HC  NH 


^^-         \^H  ^f^^ 


BENZOPYRROL  COMPOUNDS,  547 

Indol,  benzopyrrol,  CsHtN,  is  formed  on  fusing  proteids  with  caustic 
alkalies  as  well  as  in  the  putrefaction  of  the  same  and  hence  is  found  in 
feces.  It  is  also  obtained  by  the  distillation  of  oxindol  with  powdered 
zinc  and  also  by  heating  orthonitrocinnamic  acid  with  caustic  alkali  and 
iron  filings: 

It  forms  colorless,  faintly  basic  scales  having  feces-like  odor  and  which  are 
readily  volatile  with  steam.  It  can  be  obtained  from  feces,  accompanied 
by  the  skatol  and  phenols  contained  therein,  by  distillation  with  water. 
It  colors  a  pine  shaving  moistened  with  HCl  cherry-red. 

Oxindol,  CgHyNO  (see  p.  468),  obtained  by  the  action  of  sodium 
amalgam  upon  isatin  (see  below)  in  acid  solution.  It  forms  colorless 
needles  which  by  reduction  are  converted  into  indol,  CSH7N,  and  are 
converted  into  dioxindol  (see  below)  by  oxidation  in  the  air. 

Indoxyl,  urine  indican,  CgH^NO,  isomer  of  oxindol,  occurs  as  potassium 
indoxyl  sulphate,  CsH6N(0-S02~OK),  in  small  amounts  in  the  urine  of 
carnivora  and  larger  amounts  in  herbivorous  urine.  If  urine  is  carefully 
treated  with  oxidizing  substances  the  indoxyl  sulphuric  acid  is  oxidized 
to  indigo-blue,  which  can  be  shaken  out  by  chloroform,  giving  a  blue  color 
to  the  same.     On  stronger  oxidation  it  yields  isatin. 

Preparation.  From  aniline  and  chloracetic  acid  we  obtain  anilido- 
acetic  acid  (phenylglycocoll),  which  on  fusion  with  alkah  hydroxides  yields 
indoxyl: 

(CcHrNH)CHrCOOH=H20+C,H,<^g5}>CH. 

Properties.  Yellow  crystals  soluble  in  water,  alcohol,  ether,  etc., 
and  melting  at  85°.  In  alkaline  solution  it  is  oxidized  into  indigo-blue, 
even  in  the  air. 

Indoxylic  acid,  CeH^NOg  or  C8He(COOH)Np.  Preparation.  Brom- 
malonic     acid     ester     and    aniUne     yield     anilido-malonic    acid     ester: 

CHBr<gg3:g^][][«  +  CeH,NH,=  C6H,NHCH<ggg:g2|«  +  HBr,    which 

2    ^  ^    ^         POOC  H 

at  260°  yields  alcohol  and  indoxylic  acid  ester,  C6H5-NH-CH<qqqq2jj5= 

C,H,<^S"^x>C-COO-C2H6+C2H50H.     This    on    oxidation    in   alkaline 

solution  in  the  air  turns  into  indigo-blue:  2C9H6(C2H5)N03  4-02= 
CeHioN  A  +  2CO2  +  2C2H5OH. 

See  also  the  technical  preparation  of  indigo  (p.  548). 

Properties.  Colorless  prisms  which  are  oxidized  into  indigo-blue  and 
on  heating  yield  indoxyl  and  CO2. 

Dioxindol,  CgHyNOa,  is  produced  by  the  action  of  sodium  amalgam 
upon  an  alkaline  solution  of  isatin.  It  forms  colorless  prisms  and  is 
readily  oxidized  in  watery  solution  into  isatin. 

Isatin,  CrHsNOj,  formed  in  the  oxidation  of  indigo  by  nitric  acid  as 
yellowish-red  prisms  soluble  in  hot  water  and  alcohol.  It  is  artificially 
prepared  from  orthonitrophenyl  propiolic  acid  by  boiling  with  alkahes 
(see  also  p.  468) : 


548  ORGANIC  CHEMISTRY. 

C.H.<g=f-COOH^C.H.<g(^^CH+CO,. 

Skatol,  ^-methyl  indol,  CgHgN,  occurs  as  potassium  skatoxyl  sulphate, 
CgH8-N-(0'S02"OK),  in  human  urine  and  is  formed  at  the  same  time  as 
indol  in  all  the  methods  of  formation  given  for  indol.  It  forms  colorless 
scales  which  melt  at  94°,  is  much  less  soluble  in  water  than  indol,  and 
does  not  color  a  pine  chip  moistened  with  HCl.  The  odor  of  excrements 
is  chiefly  due  to  skatol  and  indol. 

Indigo-blue,  indigo,  indigotin,  CjeHioNaOg  (structural  formula  below). 
Occurrence.  It  does  not  occur  preformed.  It  is  the  chief  constituent  of 
commercial  indigo  and  may  also  be  obtained  in  small  amounts  from 
urine  (see  Indoxyl). 

Preparation  of  Natural  Indigo.  Various  varieties  of  Indigofera  of 
India  and  America,  also  Isatis  tinctoria  (woad),  Polygonum  and  Nerium 
tinctorium  contain  the  glucoside  indican,  Cj^HiyNOe,  which  by  fermenta- 
tion (if  the  plants  are  moistened  with  water  and  allowed  auto-fermenta- 
tion) or  by  boiling  with  dilute  acids  decomposes  into  glucose  and  indoxyl, 
which  is  oxidized  in  the  air  into  indigo:  Ci4Hi7N06  +  H20=C8H7NO  + 
CeHigOe,  the  indigo  depositing  as  a  blue  powder. 

Preparation  of  Pure  Indigo.  1.  By  the  careful  sublimation  of  com- 
mercial indigo  or  from  indigo  white  (p.  549). 

2.  From  orthonitrophenyl  propioUc  acid  (p.  502)  by  reducing  agents 
(grape-sugar,  etc.)  in  alkaline  solution: 

2CeH,<^0  +     4H     =       I  II 

'    NO2  l!jH— C==C— NH    +2C0, 


o-nitrophenylpropiolic  acid,  C9H6NO4.  Indigo ,  C16H10N2O2. 

We  can  therefore  consider  indigo  blue  as  a  double  compound  of  the 
groups  C6H4<^Vt>C=,  and  in  its  formation  from  indol  bodies  a  combina- 
tion of  two  indol  groups  must  take  place. 

3.  From  o-nitrobenzaldehyde  and  acetone  in  alkaline  solution: 

2C6H,(N02)  (CHO)  +  2C3H60= CieHjoN  A  +  ^G,Up,  +  2H2O. 

4.  Besides  these  methods  indigo  blue  can  be  obtained  in  various  ways; 
i.e.,  from  most  indol  bodies  (p.  547). 

Technical  Preparation  of  Indigo.  As  the  above  methods  for  preparing 
artificial  indigo  are  too  expensive,  the  following  method  is  used  in  its 
technical  preparation: 

Anthranilic  acid,  C6H,(NH^)(C00H),  which  can  be  prepared  m  quan- 
tities sufficiently  great  and  cheaply  from  naphthalene  (p.  514),  is  converted 
into  phenylglycocoU  carboxylic  acid  by  monochloracetic  acid,  and  on 
heating  with  alkali  hydroxides  it  yields  indoxylic  acid: 

which  in  alkaline  solution  on  oxidation  by  the  air  precipitates  crystalline 
indigo-blue  (process,  see  above). 

Properties.  Dark-blue  powder  with  reddish  lustre  which  sublimes 
at   300°.      It  is  without   odor  and  taste,   insoluble   in   water,    alcohol, 


FURANE  COMPOUNDS.  549 

ether,  dilute  acids,  and  alkalies.  It  is  soluble  in  chloroform,  aniline,  oil 
of  turpentine,  paraffin,  phenol,  and  benzene.  On  fusion  with  alkali  hy- 
droxides, indoxyl,  salicylic  acid,  anthranilic  acid  (o-amidobenzoic  acid), 
and  aniline  are  obtained  according  to  the  temperature.  On  oxidation  it 
yields  isatin,  and  on  reduction  we  obtain  indigo  white.  It  dissolves  in 
very  concentrated  or  better  in  fuming  sulphuric  acid,  forming 

Indigomonosulphonic  acid,  CieH^NaOaCSOg)!!,  and 

Indigodisulphonic  acid,  Ci6H8N202(,S03'H)^,,  which  are  used  in  the  dyeing 
of  wool.  Its  sodium  salt,  Ci6HjjN202(S03'Na)2,  which  is  soluble  in  water 
with  a  blue  color,  is  called  indigo  carmine. 

Indirubin,  indigo  purpurin,  Ci6HioN202,  an  isomer  of  indigo  blue, 
occurs  in  commercial  indigo  blue,  and  is  produced  besides  indigo  blue  on 
the  decomposition  of  the  indoxyl  sulphuric  acid  of  the  urine  by  HCl. 
.It  forms  brownish-red  shining  needles. 

Indigo  white,  C16H12N2O2,  is  produced  from  indigo  blue  by  reduction 
with  ferrous  sulphate  or  grape-sugar  in  alkaline  solution.  The  indigo  and 
Ihese  substances  are  mtxed  with  water  and  filled  completely  into  a  flask, 
which  is  closed  and  allowed  to  stand  (indigo  of  the  dyer).  The  yellow 
solution  obtained  is  treated  with  HCl,  the  air  being  excluded,  when  the 
indigo  white  precipitates  as  a  white  crystalline  powder,  which  is  oxidized 
to  indigo  blue  in  the  air  (preparation  of  pure  indigo  blue  from  the  com- 
mercial indigo).  Indigo  white,  in  contradistinction  to  indigo  blue,  dis- 
solves in  alcohol,  ether,  and  alkalies.  This  last  property  is  made  use  of  in 
dyeing. 

The  dyeing  is  done  according  to  two  methods:  The  material  to  be 
dyed  is  dipped  in  an  aqueous  solution  of  indigo  sulphonic  acid  (Saxon- 
blue  dyeing),  or  the  material  is  dipped  in  the  indigo  solution  as  above 
described,  and  then  exposed  to  the  air,  when  the  indigo  white  is  oxidized 
to  indigo  blue,  which  deposits  in  the  tissues. 

3.  Furane  Compounds. 

Furane,  furfurane,  tetrol,  C^H^O,  or  <QH=Qfj>C>,  occurs  in  the  first 

distillate  of  pinewood-tar  and  in  the  distillation  of  pyromucic  acid,  CgH^O.,, 
with  soda-lime.  It  is  a  neutral  fluid,  insoluble  in  water,  boiling  at  32°, 
and  having  a  peculiar  odor.  It  colors  a  pine  chip  moistened  with  HCl 
green. 

Furanalcohol,  C4H3(CH20H)0,  found  in  the  products  obtained  on 
roasting  coffee,  is  prepared  from  its  aldehyde.  It  is  a  colorless  liquid 
boihng  at  170°. 

Furol,  furanaldehyde,  furfurol,  C4H3(CHO)0,  a  decomposition  product 
of  certain  proteids,  occurs  in  beer  and  brandy,  and  is  produced  in  the 
distillation  of  bran  (furfur),  seaweeds,  pentoses,  and  pentosanes  (p.  444) 
with  dilute  sulphuric  acid.  It  is  a  colorless  aromatic  liquid  boiling  at 
162°,  and  which  turns  brown  in  the  air.  Sesame-oil  is  colored  cherry-red 
by  HCl  and  an  alcoholic  solution  of  furfurol  (use  of  furfurol  in  the  detec- 
tion of  margarine,  which  in  Germany  must  contain  sesame-oil). 

Pyromucic  acid,  furancarboxylic  acid,  C4H3(COOH)0,  is  obtained  by 
the  oxidation  of  furol  as  well  as  in  the  dry  distillation  of  mucic  acid, 
CsHioOg.     It  forms  colorless  needles  which  melt  at  134°. 

Furoin,  C4H30-CO-CH-OH-C,H30,  is  produced  from  furol  in  a 
manner  similar  to  benzoin  from  benzaldehyde  (p.  488).   It  melts  at  135°. 


550  ORGANIC  CHEMISTRY, 

Benzofurane,  coumarone,  CoH4<q_^CH,  bears  the  same  relationship 

to  furane  as  indol  bears  to  pyrrol.  It  occurs  with  its  homologues  in  coal- 
tar  and  is  an  indifferent  oily  liquid. 

4.  Thiophene  Compounds. 

Thiophene,  C^H^S  or  <nH  =  CH'^^'  ^^^^^^  ^^*^  methylthiophene 
(thiotolene)  and  dimethylthiophene  (thioxene)  to  a  slight  extent  in  the 
Ught  oils  of  coal-tar  (p.  473)  and  therefore  occurs  in  crude  benzene. 

It  is  produced  by  heating  succinic  anhydride  with  P2S3: 

<  CH^-CO  -^  ^  "^  ^2^3  =  <  CH=CH  -^  ^  "^  ^2^2  +  ^21 

or  by  passing  acetylene  through  boiling  sulphur:  2C2H2  + 8=041148.  It 
is  a  colorless  neutral  Uquid  boiling  at  84°,  which  with  isatin  and  sulphuric 
acid  forms  blue  indophenin,  C12H7NOS  (deUcate  reaction  for  thiophene). 

Thiophenic  acid,  0^113(00011)8,  very  similar  to  benzoic  acid,  is,  like 
aU  thiophene  derivatives,  known  as  two  isomers  (a  and  /?). 

OH 

Benzothiophene,    thionaphthene,   OeH4<g_^OH,   bears    the    same 

relation  to  thiophene  that  benzofurane  does  to  furane.  It  forms  colorless 
crystals. 

OH 0 OH 

Thiophtene,     ||  ||        J]     ,    is  related  to  thiophene  in  the  same 

CH~S~C~S"~CH 
manner  as  naphthalene  to   benzene,  and  is  produced  by  heating  citric 
acid  with  P2S3.     It  forms  a  thick  liquid  boiling  at  225°. 

FIVE-MEM BERED    COMPOUNDS    CONTAINING    SEVERAL    OTHER 
ATOMS  IN  THE  CARBON  RING. 

The  most  important  compounds  of  this  group  are  those  containing 
nitrogen,  which  are  derived  from  pyrrol,  furane,  thiophene,  indol  deriva- 
tives by  replacing  =0H-  groups  by  =N""  atoms.  They  are  called  azoles, 
and  according  to  the  number  of  N  atoms  in  the  ring  di-,  tri-,  tetrazoles. 
Oxazoles  contain  one  N  and  one  O  atom;  thiazoles,  one  N  and  one  8  atom 
in  the  ring.  According  as  the  N  atoms  occupy  the  o-,  m-,  or  p-position 
to  each  other  they  are  called  oiazoUs,  miazoles,  and  piazoles  (p.  542). 

I.  Azole  Compounds. 

OH'^OH 
Glyoxaline,  O3H4N2  or  <j^==qjj>NH,  m-diazole,  imidazole,  and 

Pyrazole,  C3H4N2  or  <qjj==j^>NH,  o-diazole,  form  colorless  crystals. 

OH  ~0H 
Dihydry pyrazole,  pyrazoline,  <qjjL=_-^2>]^jj^  jg  g^  i,asic  liquid. 

OH  ""OH 
Tetrahydropyrazole,    pyrazolidine,  <cH^-;fq^jj  >NH,    is   only   known 

in  the  form  of  derivatives. 


AZOLE   COMPOUNDS,  551 

Methyldihydroimidazole,     ethylenethylenyldiamine,     lysidin, 
<j^=^,/r.Li^v  >NH,  is  used  as  a  solvent  for  uric  acid. 

Pyrazolon,  <r;HL=>T  >NH,  pyrazolin  ketone,  forms  colorless  crystals 

and  is  the  mother-substance  of 

Phenyldimethylpyrazolon,  antipyrine, 

C„H„N,0  or  CgfcH3)-N(CH°>N(C.H.), 

is  produced  by  warming  methylphenylhydrazine  with  acetoacetic  ester, 
when  a  peculiar  rearrangement  in  the  pyrazolon  ring  takes  place: 

CeHsN^H^-CHg  +  C,Hio03=  CnHi^N^O  +  H^O  +  QHeO. 

""tSre"^-       acettter.   Autipyrine.  Alcohol. 

It  is  a  white  crystalline  powder,  melting  at  113°  and  readily  soluble  in 
water  and  alcohol.  Its  dimethylamido  derivative  is  called  pyramidon,  its 
acetyl  salicylic  acid  salt  is  called  acopyrine  or  acetopyrine. 

Salipyrine,  CiiHjjNgOCCeH^-OHCOOH),  forms  a  white  sweetish  micro- 
cry  .talline  powder  or  plates,  which  are  not  readily  soluble  in  water,  but 
readily  soluble  in  alcohol.     It  melts  at  92^. 

Indazole,  C7H6N2  or  C6H^<'   |     yNH,  benzopyrazole,  and  its  isomer, 

pTT 

Isindazole,   CyHgNa  or  C6H^<^pj^N,  is   indol,  in  which  one  =CH- 

group  is  replaced  by  a  =N~  atom.     They  form  crystals  having  weak  basic 
properties  and  are  the  mother-substance  of  many  compounds. 
.N=CH-C-NHv 
Purin,  CsH.N,  or  HC^  II  ^CH,  the  mother-substance  of 

^N C N^ 

the  uric  acid  group  (p.  416),  is  a  diazindiazole  which  may  be  considered 
as  benzopyrrol,  CgHyN  (p.  547),  in  which  three  =CH-  groups  are  replaced 
by  three  =N~  atoms. 

Osotriazole,  C2H3N3  or  <Qi-j=isf  >NH,  pyrro  (aaO  diazole,  forms 
colorless  crystals  which  melt  at  22°; 

Pyrrodiazole,  C2H3N3  or  <™Ir^>NH.  pyrro  (ah)  diazole,  melts  at 
111°; 

Triazole,  C2H3N3  or  <^I^^>NH,  pyrro  (660  diazole,  melts  at  121°, 

are  all  derived  from  pyrrol,  C4H4N,  by  substituting  two  =CH-  groups  by 
=N"-  atoms,  and  hence  are  called  pyrrodiazoles.  They  with  their  deriva- 
tives are  weak  bases. 

Tetrazole,    CH2N4    or    <^?^^>NH,  forms   crystals  which  melt  at 

155°,  having  an  acid  character.     Its  salts  explode. 


552  ORGANIC  CHEMISTRY. 


1,  Oxazole  and  Thiazole  Compounds. 

Oxazole,  C3H3NO  or<™^™>0. 
Isoxazole.CgHgNO  or  <^^ZSJ^>0. 

Azoxazole,  C^H^N^O  or  <CH=N^^- 

These  three  do  not  exist  free,  but  they  are  the  mother-substance  of 
various  compounds  and  they  are  derived  from  furane,  C^H^O,  by  replacing 
one  or  two  =CH-  groups  by  one  or  two  =N-  atoms.  Oxazole  and  isoxazole 
are  therefore  called  furomonoazole  and  azoxazole  is  called  furodiazole  or 
furazan. 

Thiazole,  C3H3NS  or  <^T__QyT>S,  thiomonazole,  is  thiophene,  C^H^S, 

in  which  one  =CH-  group  is  replaced  by  a  =N~  atom  and  forms  a  basic 
hquid  boiUng  at  117°. 

/CH=CH-C-Sv 
Benzothiazole,  C^H.NS  or  <  11        >CH,  melts   at    134°  and 

\CH=CH-C-N/ 
forms  the  thiazole  dyes  by  the  introduction  of  amido,  alkyl,  and  alphyl 
groups.     These  dyes  are  called  erica,  primulin,  thiazole  yellow,  thioflavin, 
which  dye  without  mordants. 

.CH=CH-C-Nv 
Benzothiodiazole,  CgH.NoS  or  <^  11    I    >S,  piazthiol,  melts  at 

\CH=CH-(^-N/ 
44°,  seems  to  be  the  mother-substance  of  the  sulphur  dyes  (immedial 
black,  vidal  black),  which  dye  without  mordants. 

ALKALOIDS. 

Alkaloids,  plant  bases,  is  the  name  given  to  nitrogenous  carbon 
compounds  occurring  in  the  plants  and  having  pronounced  basic 
(alkali-like)  characteristics  and  which  are  derivatives  of  simple  or 
combined  heterocarbocyclic  or  combined  iso-  and  heterocarbocyclic 
rings  and  therefore  show  in  their  behavior  a  great  similarity  with 
each  other.  They  generally  form  the  physiologically  active  constituent 
of  the  plants  and  most  of  them  are  strong  poisons. 

All  the  nitrogenous  carbon  compounds  occurring  in  the  plants 
and  having  basic  properties,  such  as  betaine,  choline,  muscarine, 
caffeine,  theobromine,  asparagine,  etc.,  used  to  be  considered 
as  alkaloids.  The  oxygen-free  alkaloids  coniine,  nicotine,  piperi- 
dine,  sparteine  have  a  characteristic  odor,  are  colorless  volatile 
liquids,  while  the  others  contain  oxygen  and  are  odorless,  crys- 
tallizable,  non-volatile,  generally  colorless  solids.  All  are  soluble 
in  alcohol,  benzene,  chloroform,  amylalcohol,  and,  with  the  ex- 
ception   of    morphine    and    narceine,    also    soluble   in   ether.       All 


ALKALOIDS.  553 

with  the  exception  of  nicotine  are  difficultly  soluble  in  water.  The 
solutions  have  a  bitter  taste  and  an  alkahne  reaction.  They  have 
the  character  of  amine  bases  and  combine,  hke  these,  with  acids  by 
addition,  forming  good  crystalline  salts,  which  are  soluble  in  water  and 
alcohol  and  insoluble  in  ether  with  the  exception  of  colchicine.  The 
free  alkaloid  is  precipitated  from  the  aqueous  solution  of  its  salts  by 
alkah  hydroxides  and  alkali  carbonates.  They  are  mostly  optically 
active  and  indeed  laevorotatory.  Coniine,  quinidine,  cinchonine, 
pilocarpine,  are  dextrorotatory,  and  piperine,  papaverine,  berberine, 
and  atropine  are  inactive. 

They  are  precipitated  from  their  solution  by  tannic  acid,  phospho- 
molybdic  acid,  and  phospho-tungstic  acid  (p.  271),  potassium-mer- 
curic iodide,  potassium-cadmium  iodide,  and  a  great  many  by  iodine. 
Their  hydrochloric  acid  compounds  are  precipitated  by  platinum 
chloride  as  a  double  crystalline  salt,  similar  to  ammonium  salts  (p. 
317)  and  amine  bases. 

In  preparing  them  the  parts  of  the  plants  are  extracted  with  dilute 
hydrochloric  acid.  The  volatile  alkaloids  can  be  obtained  from  this 
solution  by  distillation  with  caustic  alkali.  In  order  to  separate  the 
non-volatile  alkaloids  the  solution  is  generally  first  precipitated  by 
lead  acetate  in  order  to  remove  tannin  bodies,  pigments,  and  gluco- 
sides,  and  the  filtrate  freed  from  lead  by  HgS,  and  the  alkaloids  pre- 
cipitated from  this  filtrate  by  caustic  alkalies.  This  precipitate  is 
dissolved  in  alcohol  and  repeatedly  recrystallized. 

I.  Pyridine  and  Pyrrol  Compounds. 

Trigonelline,  C7H7NO2  +  H2O,  nicotinic  acid  methyl  botaine  (pp.  369 
and  539),  occurs  in  the  seeds  of  Trigonella  fcenumgrsecum,  and  the  seeds 
of  Strophantus  hispudus.     It  forms  neutral  prisms. 

Hygrine,  CsHi.NO,  C,H7(CH3)(COC2H,),  methylpyrrolidine  ethyl 
ketone,  forms  a  liquid  which  turns  brown  in  the  air  and  which  occurs  to 
a  slight  extent  in  coca  leaves  (p.  558). 

Piperine,  CjyHjgNOs,  piperylpiperidine,  occurs  in  ordinary  and  long 
pepper,  decomposes  on  boiling  with  alkali  hydroxides  into  piperic  acid 
Ci^H^oO,  (p.  501).  and  piperidine,  C,H,oNH  (p'.  539). 

Pilocarpine,  C,,H, 81^2^)2.  pilocarpidine,  Ci.jHj^NoOa,  jaborine,  CajH^aN^O^, 
occur  together  in  the  leaves  of  Pilocarpus  pennatifolius.  Pilocarpine  is 
soluble  with  a  green  color  in  fuming  nitric  acid  and  blackens  on  rubbing 
with  an  equal  quantity  of  mercurous  chloride  and  moistening  with  alcohol. 

Pilocarpine  hydrochloride,  CnHjeNgOg'HCl,  forms  crystals  which  melt 
at  194°. 

Arecaidine,  C^H^NOj,  tetrahydromethyl  nicotinic  acid  (p.  530),  areco- 
UnCjCgHiaNOa  (methylarecaidine),  guvacine,  CeHgNOgi  (tetrahydromethyl- 


654  ORGANIC  CHEMISTRY, 

dioxypyridon,  p.  532),  rnd  arscaine,  C7H11NO2  (methyl  guvacine),  occur 
in  the  areca-nut  (Semen  areca?). 

Coniine,  Cj,Hi7N  (d-hexahydropropylpyridine,  d-propyl  piperidine, 
p.  539),  conhydrine  and  pseudo-conhydrine,  C8H17NO  (both  oxyconiines), 
as  well  as 

Coniceine,  CgHigN  (i-tetrahydropropylpiperidine) ,  occur  together  in 
the  hemlock  (Herba  conii).  Coniine  forms  a  liquid  having  a  narcotic 
odor,  boiling  at  16S°,  dextrorotatory  and  very  poisonous.  It  turns 
brown  in  the  air  and  becomes  thick.     A  trace  of  coniine  gives  a  bluish- 

green  coloration  when  heated  with  metaphosphoric  acid. 
H2~CH        CH2  Pseudopelletierine,    C9H15NO,    contains    two    con- 

I         I  I  densed  pyridine  rings  and  forms  crystals.     It  is  found 

CH2  NCH3  CO      with  the  liquid  alkaloids  pelletierine  and  isopelletierine, 

I         I     I  C,Hi5xN0,    and    methylpelletierine,   C^Hi^NO,    in    the 

CH2~CH        CHj     pomegranate-root. 

Nicotine,  CjoH^^Ng,  d-pyridyl-/?-tetrahydro-n-methyl  pyrrol,  is  found 
/N\  CH  ^^  ^^^  leaves  of  the  tobacco  (Nicotiana  tabacum) 

^    \  I      ^         and  the  seeds  of   the  tobacco.     It  forms  a  very 

I  11  /N\  poisonous  liquid  having  a  narcotic  odor  and  boil- 

L        li,      ^    \         ing  at  247°  and  soluble  in  water.     It  turns  brown 
\      /        I  1  "^  ^^^  ^^^  ^^^  when  heated  with  metaphosphoric 

^,/        1^, ,1   -.      acid  it  gives  an  orange  color. 

Url         Cxlj     Cxlj 

2.  Quinoline  Compounds. 

a.  Alkaloids  of  the  Strychnos. 

Strychnine,  C21H22N2O2,  contains  a  condensed  quinoline-piperidone 
(=  a-ketopiperidine)  ring  or  quinoline- pyrrolidone  (=  a-ketopyrrolidine) 
ring  and  is  found  with  brucine  in  the  Nux  vomica,  in  the  St.  Ignatius 
bean,  and  in  the  wood  of  the  Strychnos  colubrina. 

It  forms  colorless,  instenely  bitter  crystals  which  with  concentrated 
sulphuric  acid  and  some  potassium  bichromate  give  an  intense  bluish- 
violet  solution  which  gradually  changes  to  red  and  then  yellow. 

Strychnine  nitrate,  C2iH22N202*HN03,  forms  colorless  needles  having 
a  persistent  bitter  taste  and  soluble  in  90  parts  water. 

Brucine,  C23H26N2O4  +  4H2O,  dimethyloxylstrychnine,  occurs  also  in 
the  bark  of  the  Strychnos  Nux  vomica  and  forms  colorless,  laevorotatory 
crystals,  which  give  a  red  color  with  nitric  acid  (test  for  nitric  acid) 
which  on  warming  turns  yellow.  On  the  addition  of  SnClj  the  yellow 
color  becomes  violet. 

Curarine,  CigH^eNgO,  the  active  constituent  of  the  extracts  of  various 
varieties  of  Strychnos  and  called  curare  or  urari  and  which  is  used  as  an 
arrow  poison.  It  forms  a  brown  amorphous  powder  which  turns  violet 
with  sulphuric  acid  and  red  with  nitric  acid. 

c.  Alkaloids  of  the  Cinchona. 

The  bark  of  the  various  species  of  cinchona  contain  the  four  following 
alkaloids  combined  with  quinic  acid  (p.  496) : 

Quinine,       C20H24N2O2;  Quinidine,      C20H24N2O2; 

Cinchonine,  CiBHazNgO;  Cinchonidin,  CieH22N20. 


H,C     • 


ALKALOIDS.  555 

They  are  derivatives  of  a  quinoline  and  a  complicated  piperidine  ring 

(see  Quinine). 

Quinine  and  quinidine  are  readily  soluble  in  ether,  cinchonine  and 

cinchonidine  are  nearly  insoluble  therein.     If  to  an  aqueous  solution  of  a 

quinine  or  quinidine  salt  we  add  chlorine  water  and  then  ammonia  we 

obtain  a  beautiful  emerald-green  coloration. 

Cinchonine,  C19H22N2O  (structure,  see  Quinine),  forms  bitter  prisms 

which  are  difficultly  soluble  in  alcohol  and  which  melt  at  255°. 

Quinine,  C20H24N2O2,  methyloxylcinchonine,  exists  to  about  6  per  cent. 

in    the    cinchona    bark,    forms    with 

3BL0,  shining  bitter  needles  which  are 

difficultly  soluble   in  alcohol.      When 

anhydrous  they  melt  at  175°,     It  forms 

Y(TT_pTT=pTT  primary  and    secondary   salts,  which 

I        C-Ont      ^    ^^    2  latter  are  nearly  insoluble  in  water. 

TT  X        I  Utt  Quinine  bisulvhate, 

\  y      "  (C2oH2,N202)H,SO,  +  7H2O, 

y\  rtiT  -n  u  rn.nxy  nxt    forms  colorless  crystals  which  dissolve 
^jJj/XCH^  C,H,(0CH3)N    j^  jQ  p^^^g  ^^^^^ 

Quinine  sulphate,  (C2oH24N202)2H2SO,+8H20,  is  not  readily  soluble  in 
water  but  more  soluble  than  the  bisulphate  by  the  addition  of  some 
sulphuric  acid. 

Quinine  hydrochloride,  C2oH24N202*HCl  +  2H20,  white  crystalline 
needles,  soluble  in  34  parts  water. 

Quinine-iron  citrate  is  readily  soluble  in  water. 

Quinine  tannate,  yellow  amorphous  powder  soluble  with  difficulty. 

Quinine  carboxylic  acid  ethyl  ester,  C2oH23(COO'C2H5)N202,  euquininef 
serves  as  a  tasteless  substitute  for  quinine, 

Cinchonidine,  Ci9H22N20,  the  stereiosomer  of  cinchonine,  also  obtained 
from  cinchonine  by  rearrangement  of  the  molecule,  forms  large  prisms 
which  melt  at  203°  and  are  readily  soluble  in  alcohol. 

Quinidine,  C20H24N2O2,  methyloxylcinchonidine,  forms  prisms  with 
2 J  molecules  H^O  and  when  anhydrous  melts  at  172°. 

3.  Isoquinoline  Compounds. 

Hydrastine,  CgiHgiNOe,  occurs  in  Hydrastis  canadensis  (Golden  seal), 

CH        CH  forms    prisms    melting  at    132°  and    on 

/      \y        "\  /^,      oxidation  yields  opianic  acid,  C.oHioO« 

/0-C  C  N<  ^i.    (p,  497),  and 

^2^\     Jl  I  I  \'-^3        Hydrastinine,  CnHigNOg.     The   salts 

^O'C  C  CH2         of    this  contain  the  complex  CnHiiNOa 

\y\       /  which   is  obtained  by  the   removal    of 

H        CH2  water. 

Hydrastinine  hydrochloride,  CnHnNOa'HCl  (see  structural  formula). 

This  forms  yellow  needles  which  melt  at  210°  and  are  soluble  in  water 
with  a  blue  fluorescence, 

Berberine,  C20H17NO4,  contains  a  hydrastinine  and  an  isoquinoline 
ring  with  a  mutual  C  and  N  atom.  It  occurs  in  the  varieties  of  Berberis,  in 
the  columbo  root,  in  the  Hydrastis  canadensis,  in  the  bark  of  the  GeofTroya 
jamaicensis,  Xanthoxylum  clava,  and  many  other  plants  used  as  a  yellow 
dye.  It  forms  yellowish-brown,  optically  inactive  needles  with  6  mole- 
cules H2O.     It  melts  at  145°. 


538  ORGANIC  CHEMISTRY. 

Papaverine,  CjoHaiNO^,  dimethyloxylbenzyldimethyl  oxylisoquinoline. 
About  1  per  cent,  is  found  in  opium  (see  below)  and  forms  optically 
inactive  prisms  which  melt  at  147°. 

Narcotine,  C22H23NO7,  methyloxylhydrastine,  exists  in  opium  (about 
6  per  cent.)  and  forms  prisms  melting  at  176°  and  which  on  oxidation 
yields  opianic  acid,  CioHioOg  (p.  497),  and 

Cotarnine,  CijHjsNO^,  methyloxylhydrastinine,  which  forms  salts 
having  the  complex  C12H13NO3;  thus,  cotarnine  hydrochloride, 
Ci2H,3NOy"HCl    is  used  in  medicine  as  stypticine. 

Narceine,  C23H27NO8  +  3H2O,  exists  in  opium  to  about  0.2  per  cent, 
and  is  closely  related  to  narcotine.  It  is  produced  from  the  methyliodide 
compound  of  narcotine  by  heating  with  bases:  C22H23N07*CH3l  +  KOH= 
C23H27NO8  +  KI.     When  anhydrous  it  forms  crystals  melting  at  145°. 

4.  Phenanthrene^Morpholine  Compounds. 

Opium,  the  dried  juice  of  the  unripe  poppy,  contains  over  20  alkaloids 
combined  with  meconic  acid  (p.  541).  The  most  important  are  papa- 
verine, narcotine,  narceine,  which  have  been  treated  with  the  isoquinoline 
derivatives,  and  morphine,  codeine,  thebaine,  which  are  phenanthrene- 
morpholine  derivatives  (pp.  518,  544). 

Morphine,  Ci7His,N03  +  H20,  exists  to  about  20  per  cent,  in  opium, 
Qjj  forms  small  prisms  which  melt  at  230°  and  is 

^      \  the  only  alkaloid  soluble  in  an  excess  of  alka- 

HC  CH2  lies  (but  not  by  ammonia).     The  solution  of 

morphine  is  lavorotatory  and  becomes  deep 
N~CH,    blue   with   ferric   chloride.      The   solution  in 


./ 


> 


P  PR  concentrated  sulphuric    acid  turns  blood-red 

II  I  I     2         with  a  trace  of  nitric  acid. 

ttH         i  CHg  Morphine   hydrochloride,  Ci7Hi9N03-HCl  + 

V     ^  V  A  3H2O,    forms   white    needles    or    cubiformed 

^r^  PH-  masses  soluble  in  25  parts  water. 

I  I  Ethyl  morphine  hyd  ochloride, 

HO-HC  COH  Ci7H,,(C2H,)N03HCl,  diomn  and 

\       ^  Morphin  diacetoacetic  ester, 

\^W  C,7H,7(CH3COO)2N03,  heroin  and 

Benzoylmorphin  hydrochloride,  Ci7Hig(C(jH5-CO)N03*HCl  +  H20,  pero- 
nin,  are  used  in  medicine  and  form  colorless  crystals. 

Apomorphine,  C17H17NO2,  morphine  anhydride,  is  produced  when 
morphine  is  heated  to  150°  for  a  long  time  with  fuming  HCl,  when  a 
molecule  of  water  is  split  off.  Amorphous  white  powder  producing  emesis 
and  which  turns  quickly  green  in  the  air. 

Apomorphine  hydrochloride,  Ci7H,7N02*HCl,  is  soluble  in  40  parts 
water,  immediately  reduces  silver  nitrate  solution  in  the  presence  of  NH3. 
Nitric  acid  dissolves  it  with  a  red  color. 

Code'ne,  C,sH2,N03  +  H20,  methyl  morphine,  exists  in  opium  (about 
0.3  per  cent.),  forms  crystals  which  when  anhydrous  melt  at  155°.  It  is  sol- 
uble in  concentrated  sulphuric  acid  and  when  treated  with  ferric  chloride 
gives  a  deep-blue  coloration. 

Codeine  phosphate,  C,sH2iN03'H3PO^  +  2H20,  forms  white,  bitter 
needles  that  are  soluble  in  3.2  parts  water. 

Thebaine,  CmHaiNOg,  is  found  in  opium  (about  0.15  per  cent.),  forms 
shining  leaves  melting  at  193°  and  which  are  soluble  in  concentrated 
sulphuric  acid  with  a  deep-red  color. 


ALKALOIDS. 


557 


5.  Pyrrolidine^Piperidine  Compounds. 

The  Solanacese  alkaloids,  atropine,  hyoscyamine,  belladonine,  scopol- 
amine, also  the  coca  alkaloids,  cocaine  and  tropacocaine,  contain  a  methyl- 
ated pyrrol  ring  (p.  544)  in  combination  with  a  piperidine  ring  (p.  539). 
They  may  also  be  considered  as  a  seven-carbon  ring  (cycloheptane)  with 
a  so-called  nitrogen  bridge.  The  mother-substance  of  these  alkaloids  \a 
tropine,  which  is  evident  from  the  following  formulae: 

Tropine,  CgH^jNO. 
,C1 


Atropine,  CiyHgiNO^. 
,C1 


C.H. 
NCH,CHOOCCOH 


H^C 


CH,       CH. 


OH 


"CH" 


Ecgonine,  C9H15NO3. 
CH 


Cocaine,  Ci^HjiNO^. 
,CH 


H2C 


CHCOOH 
NCH,CHOH 


'CH 


/ 


CH, 


CHCOOCH, 
KCHaCHCOOCeH, 
CHj 


"CH' 


Atropine,  belladonine,  hyoscyamine,  scopolamine,  cause  a  dilation 
of  the  pupils  even  in  the  smallest  quantities.  When  a  trace  of  these 
bodies  is  warmed  with  concentrated  sulphuric  acid  and  some  water  and 
potassium  permanganate  added,  an  odor  similar  to  oil  of  bitter  almonds 
IS  developed.  If  a  trace  is  dissolved  in  concentrated  HgSO^  and  some 
sodium  nitrate  added  an  orange  coloration  is  obtained  which  turns  reddish 
violet  and  then  pale  pink  when  treated  with  an  alcoholic  caustic  alkali 
solution. 

Atropine  and  hyoscyamine  are  stereoisomers  and  decompose  on  heat- 
ing with  bases  into  tropine  and  tropic  acid  (p.  502) : 

C,;H,3N03  +  H,0= C«H,,NO  +  C,H,oO,. 

Tropine.      Tropic  acid. 

On  warming  tropine  (tropanol)  and  tropic  acid  with  dilute  hydro- 
chloric acid  we  only  obtain  atropine,  as  any  hyoscyamine  formed  is  imme- 
diately changed  into  atropine. 

As  tropine  combines  with  tropic  acid  so  it  also  combines  with  other 
oxyacids,  producing  compounds  called  tropeines.  With  mandelic  acid 
(p.  498)  and  tropine  we  obtain  homatropine,  CjeHjiNOa,  which  is  used  in 
medicine  instead  of  atropine. 


558  ORGANIC  CHEMISTRY. 

Homatropine  hydrohromide,  CiflH2iN03*HBr,  forms  crystals  readily- 
soluble  in  water. 

Atropine,  C17H23NO3,  i-tropic  acid-i-tropine  (structure,  see  p.  557), 
occurring  especially  in  the  deadly  nightshade,  thorn-apple,  and  henbane, 
crystallizes  in  colorless  prisms  which  melt  at  114°.  Natural  atropine  is 
inactive,  although  active  atropine  has  been  obtained  from  dextro-  and 
laevo-tropic  acid  and  i-tropine  (see  p.  557). 

Atropine  sulphate,  (Ci7H23N03)2H2SOj,  forms  colorless  crystals  which 
dissolve  in  1  part  water  and  melt  at  180°. 

Hyoscyamine,  daturin,  C17H23NO3,  occurs  in  henbane  (Folia  hyoscyami), 
in  the  leaves  of  Duboisia  myoporoides  with  atropine,  in  the  deadly 
nightshade,  and  in  the  thorn-apple.  It  crystallizes  in  fine  needles  which 
melt  at  10j>°  and  is  then  converted  into  atropine  and  is  Isevorotatory 
and  is  probably  Z-tropic  acid  tropine. 

Belladonine,  C17H21NO2,  atropanine,  atropine  anhydride,  is  contained 
in  the  Atropa  belladonna,  and  is  stereoisomeric  with  apoa^ro/>ine,  C17H21NO2, 
which  is  prepared  from  atropine  an^  hyoscyamine  by  splitting  off  of  HjO 
and  which  melts  at  60°  and  is  then  converted  into  belladonine. 

Scopolamine,  C17H21NO.,,  hyoscine,  duboisine,  occurs  in  the  scopolia 
and  belladonna  root,  in  henbane  and  thorn-apple,  in  the  leaves  of  Duboisia 
myoporoides.  It  forms  Isevorotatory  prisms  which  split  on  boiling 
with  bases  into  atropic  acid  (p.  531)  and  scopoline  (oxytropine,  oscine), 
Ci7H2iN04=C9H802  +  C8Hi3N02.  It  can  be  converted  into  i-scopolamine 
(atroscine) . 

Scopolamine  hydrohromide,  Ci7H2iNO/HBr,  forms  colorless  crystals 
which  are  readily  soluble  in  water  and  which  melt  at  180°. 

Cocaine,  C17H21NO4,  benzoyl  ecgonine  methyl  ester  (structure,  p.  557), 
occurs  in  the  South  American  coca  leaves;  forms  Isevorotatory  prisms 
which  melt  at  9S°  and  produce  local  anaesthesia.  On  boiling  with  water  it 
decomposes  into  methyl  alcohol  and  benzoyl  ecgonine,  CyH,^(C6H5-CO)N03, 
and  on  boiling  with  acids  or  bases  it  yields  methyl  alcohol,  benzoic  acid, 
and  Z-ecgonine,  CgHjjNOg  tropine  carboxylic  acid).  The  reverse  may 
also  be  brought  about  from  these  constituents,  and  this  is  of  importance, 
as  Z-ecgonine  can  be  readily  obtained  in  large  quantities  from  the  amor- 
phous residues  from  the  cocaine  manufacture. 

Cocaine  hydrochloride,  C,7H2iN04-HCl,  forms  prisms  which  melt 
at  183°  and  are  readily  soluble  in  water  and  alcohol.  The  mixture  of 
equal  parts  cocaine  hydrochloride  and  mercurous  chloride  turn  black 
when  mQistened  with  alcohol. 

Tropacocaine,  CisHjgNOg,  benzoyl  pseudotropine,  occurs  in  the 
Japanese  coca  leaves,  is  a  powerful  anaesthetic,  less  poisonous  than 
cocaine,  and  melts  at  49°. 

6.  Alkaloids  of  Unknown  Constitution. 

Aconitine,  Cg^H^jNOn,  occurs  besides  picroacontine,  C^oH^sNOio,  in 
the  leaves  and  the  roots  of  Aconitum  napellus  (monkshood),  and  to  a 
less  extent  also  in  other  varieties  of  the  aconitum  genus.  It  forms  color- 
less crystals  having  a  sharp  but  not  bitter  taste.  On  boiling  with  water 
it  decomposes  partly  into  acetic  acid  and  picroaconitine  and  partly  into 
acetic  acid,  benzoic  acid,  and  aconine  C25H4,NO^.  A  trace  of  aconitine 
warmed  with  sirupy  phosphoric  acid  yields  an  intense  violet  solution. 
(This  reaction  is  also  given  by  delphinine  and  digitaline.)     Pseudoaco- 


ALKALOIDS.  559 

nitine,  CggH^aNOia,  from  the  tubers  of  the  Aconitum  ferox,  japaconitine, 
C34H49NOH,  from  the  Japanese  aconitum,  are  physiologically  different 
from  aconitine. 

Achilletine,  C11H17NO4,  is  produced  from  the  gluco-alkaloid  achillein, 
CaoHggNgOig,  which  occurs  in  the  Achillea  millefolium.  Achillein  decom- 
poses by  the  action  of  acids  into  glucose,  achilletine,  ammonia,  and 
aromatic  bodies. 

Cephaehne,  Cj^HjoNOg,  in  the  roots  of  the  Cephaelis  ipecacuanha  (In- 
dian physic);   forms  colorless  crystals  and  is  a  quinoline  derivative. 

Emetine,  C15H22NO2,  in  the  ipecacuanha  root,  Radix  ipecacuanhae. 

Ergotinine,  Cggri^oN^Oe,  in  the  ergot,  Secale  cornutum. 

Eserine,  physostigmine,  C15H21N3O2,  in  the  Calabar  bean.  Its  solu- 
tions soon  turn  red.  It  dissolves  in  warm  ammonia  and  turns  yellowish 
red,  and  then  leaves  on  evaporation  a  blue-  or  bluish-green  residue  which 
dissolves  in  alcohol  with  a  blue  color  and  in  a  small  quantity  of  sulphuric 
acid  with  a  green  color. 

Physostigmine  salicylate,  (Ci5H2;N302)C7He03,  forms  colorless  crys- 
tals which  are  not  readily  soluble  in  water,  while  the  sulphate, 
(Ci5H2iN302)H2S04,  is  readily  soluble, 

Eserldine,  C15H23N3O3,  also  occurs  in  the  Calabar  bean. 

Jervlne,  C26H37NO3,  pseudojervine,  C29H43NO7,  rubijervine,  CjcH^gNOg 
+  H2O,  form  colorless  crystals.  They  are  found  together  in  the  white 
hellebore,  whose  most  poisonous  alkaloid  is 

Protoveratrine,  C32H5jNOii,  which  gives  a  green,  then  blue  and  violet, 
color  with  concentrated  sulphuric  acid. 

Colchicine,  C2_,H25N06,  found  in  the  seeds  of  the  Colchicum  autum- 
nale,  forms  an  amorphous  yellow  mass  which  turns  yellow  with  con- 
centrated sulphuric  acid  and  dissolves  in  concentrated  nitric  acid  with  a 
violet  coloration.  On  taking  up  water  it  splits  readily  into  colchiceine, 
C2iH23N06,  and  methyl  alcohol. 

Sinapine,  C,6H23N05,  is  not  known  free,  but  its  sulphocyanate  is  con- 
tained in  the  white  mustard-seed.  It  decomposes  by  alkalies  into  neurine 
(p.  39S)  and  sinapic  acid  (p.  501). 

Solanidine,  C^pHe.NOj,  produced  from  the  gluco-alkaloid  solanine, 
C.,2H93NO,^,  contained  in  the  potato  plant,  especially  in  the  sprouts,  and 
which  splits  into  glucose  and  solanidine  by  the  action  of  acids. 

Veratrine,  C37H53NO,j,  a  white,  amorphous  mass,  occurs  in  the  saba- 
dilla  seeds  with  the  following  crystalline  alkaloids: 

Cevadine,  C32H49NO9,  sabadinine,  CayH^gNOs,  sabadine,  CagHjiNOg, 
and  the  amorphous  cevadilllne,  C34H53NO8.  Veratrine  of  the  druggist 
is  a  mixture  of  these  alkaloids. 

Lycopodine,  C32H52N2O3,  occurs  in  the  Lycopodium  clavatum  (club- 
moss). 

Lobelline,  0,323^02,  in  the  Lobelia  inflata. 

Ricinine,  C,7H,^N^0j,  in  the  castor  seeds. 

Yohimbime,  C23H32N4O.,  forms  with  yohimbenine,  C35H4gN306,  the 
active  constituents  of  the  bark  of  the  Tabernsemontana. 


560  ORGANIC  CHEMISTRY. 

PROTEINS  OR  ALBUMINOUS   SUBSTANCES. 

These  substances,  often  confusingly  called  albuminoids,  form 
a  large  group  of  compounds  found  in  the  plants  and  animals,  which 
are  classified  according  to  their  chemical  and  physiological  behavior. 
The  name  albuminous  bodies  comes  from  the  white  of  the  egg  (albu- 
min) and  the  name  protein  substances  from  ;rpc3ro5,  the  first,  be- 
cause of  their  importance  in  the  construction  of  hving  matter.  They 
occur  to  a  sUght  extent  in  the  plants  where  the  carbohydrates,  espe- 
cially cellulose,  exist  to  the  greatest  extent,  while  they  are  found 
in  large  quantities  in  the  animal  kingdom.  Only  the  urine,  perspira- 
tion, and  the  tears  are  free  from  proteids  Under  normal  conditions. 
They  are  produced  chiefly  in  the  plants  and  suffer,  in  the  animal 
organism  during  assimilation,  only  slight  modifications  when  intro- 
duced as  plant  food.  They  occur  either  in  solution  or  as  moist, 
soft  solids  which  are  organized  in  structure  or  amorphous  masses. 

The  composition  of  different  proteids  varies  within  rather  narrow 
limits  and  amounts  to  the  following  percentages  calculated  on  the 
ash-free  substance: 

Carbon 50. 6-54. 5 

Hydrogen 6.5-7.3 

Nitrogen 15.0-17.6 

Oxygen 21 .5-23.5 

Sulphur 0.3-  2.2 

The  nucleoproteids  also  contain  some  phosphorus. 

With  the  exception  of  the  artificially  prepared  ash-free  albumins 
they  always  contain  inorganic  salts. 

Because  of  their  unp  onounced  chemical  character  and  the  ready 
decomposability  of  these  substances  no  positive  empirical  molecular 
formula  has  been  given  to  them  up  to  this  time.  No  doubt  the 
molecular  weight  is  very  high  and  the  formula  CrgHngNigOzzS  seems 
to  be  approximately  correct  for  the  albumin  of  the  egg. 

The  following  groups  of  compounds  must  take  part  in  the  construc- 
tion of  the  proteins,  as  they  are  formed  in  the  cleavage  of  all  proteins 
by  continuous  boiling  with  dilute  acids  and  bases  as  well  as  by  the 
action  of  trypsin  (see  Ferments) : 

a.  Monamido  fatty  acids  (leucin,  aspartic  acid,  glutamric  acid,  gly- 
cocoll,  cystein,  etc.).  Diamido  fatty  acids  (lysin,  diamido  acetic  acid, 
arginin,  histidin,  ornithin,  cystin). 


PROTEINS  OR  ALBUMINOUS  SUBSTANCES.  561 

The  fatty  acids  below  caproic  acid  in  the  series  which  are  produced 
by  treatment  with  acids  or  bases  or  by  energetic  oxidation  are  no  doubt 
produced  from  the  compHcated  compounds  first  spht  off  from  the  pro- 
teins, and  the  same  is  true  for  the  ammonium  carbonate,  sulphide,  and 
cyanide  formed  in  the  dry  distillation  of  these  bodies. 

b.  Isocarbocyclic  compounds  (phenol,  benzoic  acid,  tyrosin,  phenylgly- 
cocoll,  phenylpropionic  acid,  etc.). 

c.  Heterocarbocychc  compounds  (pyridine,  indol,  skatol,  furol, 
pyrrolidine  carbonic  acid,  etc.). 

Superheated  steam  produces  atmidalbumin,  which  stands  between 
the  proteoses  and  proteins,  then  atmidproteoses,  then  peptones,  and 
finally  amido  acids. 

On  oxidation  with  KMnO^  in  acid  solution  only  a  little  NHg  is  pro- 
duced, but  on  the  contrary  large  amounts  of  urea,  also  oxyprotsulphonic 
acid,  and  then  peroxyprotsulphonic  acid,  bodies  of  unknown  constitution 
but  related  to  the  protein  substances. 

Tryptophan  is  a  chromogen  (p.  £30)  produced  on  the  cleavage  of 
proteins  by  means  of  trypsin,  etc.,  which  gives  a  violet  pigment  on 
oxidation. 

From  the  decomposition  products  it  seems  as  if  these  compounds 
all  contained  some  common  groups  having  a  relatively  simple  struc- 
ture and  which  also  exist  free  in  the  spermatozoa  of  fishes  and  called 
protamins;  for  example,  salmine,  CgoHgyNi^Og,  of  the  salmon;  the 
sturine,  CgeHegNigOr,  of  the  sturgeon.  On  careful  treatment  with 
acids  the  protamines  form  protones  which  are  similar  to  the  peptones 
(p.  568)  and  which  by  stronger  action  are  converted  into  hexon 
bases,  i.e.: 

C3oH67N,,0«+  4H3O  =  CeH,N30,+  3CeH,,N  A+  CeH,,N  A- 

Salmin.  Histidin.  Arginin.  Lysin. 

The  hexon  bases  can  be  converted  into  hexoses  (glucose) ,  which 
explains  the  splitting  off  of  sugar  (glucose,  etc.)  from  different  albu- 
minous substances.  The  complex  protein  substances  are  probably 
produced  by  the  substitution  of  amido  compounds,  etc.,  in  the  pro- 
tamins, and  the  most  comphcated  formed  by  the  combination  of 
these  with  other  atomic  groups.  For  instance,  the  blood  pigments 
are  formed  by  the  combination  of  a  proteid  with  a  pigment  and  the 
nucleoproteid  by  the  union  of  a  proteid  with  the  phosphorized  nucleic 
acids. 

Properties.  In  the  solid  state  they  are  white,  flocculent  or  lumpy 
masses  without  odor  and  taste,  and  when  dry  are  yellow,  transparent, 
and  brittle  like  horn.  Besides  the  protein  crystals  which  occur  in 
certain  seeds  we  have  also  been  able  artificially  to  obtain  ovalbumin 
and  seralbimiin  in  a  crystalHne  state.     Only  a  few  are  soluble  in 


562  ORGANIC  CHEMISTRY. 

water,  but  all  dissolve,  with  partial  decomposition,  in  caustic  alkalies, 
forming  alkali  albuminates  and  in  concentrated  mineral  acids,  form- 
ing acid  albuminates  (p.  568).  The  proteids  are  insoluble  in  ether, 
chloroform,  carbon  disulphide,  benzene.  Only  the  proteids  of 
gluten  are  soluble  in  alcohol.  With  the  exception  of  peptone  they 
give  insoluble  compounds  with  many  aldehydes.  The  solutions 
of  all  proteids  rotate  the  ray  of  polarized  light  to  the  left,  with  the 
exception  of  haemoglobin,  the  nucleins,  and  nucleoproteids,  which 
are  dextrorotatory. 

Color  Reactions,  a.  On  heating  with  cone,  nitric  acid  the  proteids 
or  their  solution  tarn  yellow  and  then  deep  orange  on  the  addition 
of  ammonia  {xanthropr oleic  reaction),  b.  On  boiling  with  Miilon's  re- 
agent (solution  of  Hg(N03)2  in  HNO3  +  HNO2)  they  become  purple-red, 
or  when  applied  to  a  solution  containing  small  quantities  of  proteid  it 
becomes  red  {Millon's  test),  c.  If  to  a  solution  of  proteid  in  glyoxylic 
acid  (or  acetic  acid)  concentrated  sulphuric  acid  is  added,  we  obtain  a 
violet  coloration  which  shows  characteristic  absorption  bands  in  the 
spectroscope  {Adamkiewicz's  reaction),  d.  If  a  solution  of  proteid  is 
treated  with  caustic  alkali  and  a  few  drops  of  dilute  CuSO^  solution,  a  bluish- 
violet  coloration  is  obtained  (biuret  test). 

Precipitation  Reactions.  The  proteids  are  precipitated  from  their 
solutions:  a.  By  potassium  ferrocyanide  after  acidification  with  acetic 
acid.  b.  By  nitric  acid  when  added  in  sufficient  amount  to  the  boiling 
hot  solution  to  make  the  solution  acid.  c.  By  tannin,  basic  lead  ace- 
tate, and  most  metallic  salts  (use  of  proteids  as  antidotes  in  metallic 
poisoning),  d.  By  treating  the  solution,  acidified  with  acetic  acid,  with 
an  equal  volume  of  a  saturated  solution  of  sodium  sulphate  and  heating 
to  boiling  or  by  saturating  the  acidified  solution  with  sodium  chloride. 
e.  Faintly  acid  solutions,  especially  with  acetic  acid,  coagulate  readily 
on  boiling,  especially  in  the  presence  of  inorganic  salts  of  the  alkali  metals. 
The  coagulation  temperatures  are  different  for  the  various  proteid  bodies 
and  can  be  used  in  their  identification  and  separation.  /,  Trichlor- 
acetic acid,  metaphosphoric  acid,  and  many  of  the  so-called  alkaloid 
reagents  (see  Alkaloids)  precipitate  the  proteids.  In  these  precipita- 
tions, with  the  exception  of  the  neutral  salts,  the  proteins  are  chemically 
changed. 

Numerous  preparations  of  proteid  bodies  are  used  in  medicine;  thus, 
halogen  compounds  as  albacide  and  eigone,  ichthyol  compounds  as 
ichthalbin,  tannin  compounds  as  tannalbin,  silver  compounds  as  jrro- 
targol,  largin,  and  argonin,  the  iodoform  compound  as  iodoformogen, 
the  formaldehyde  compound  as  formolalbumin,  those  of  iron  as  ferratin, 
hcematin,  hamatogen,  hcemalbumin,  iron  somatose,  eubiol,  dynamogen, 
roborin,  fersan,  ferratogen.  Readily  digestible  products  prepared  from 
animal  and  vegetable  proteids  are  used  as  foods;  thus  from  the  residues 
from  the  preparation  of  meat  extracts  we  obtain  soson  and  tropon,  from 
skimmed  milk,  plasmon,  sariatogen,  galactogen,  from  blood  serum,  proto- 
plasmin,  from  plant  proteids,  eucasein  (ammonium  caseate),  nutrose 
(sodium  caseate),  mutase,  aleuronate  (p.  567).     As  the  peptones  (p.  568) 


NATIVE  OF   TRUE  FRO  TEWS.  563 

have  a  bitter  taste  and  the  proteoses  (p.  568)  are  tasteless  these  latter 
are  used  in  medicine  as  foods;  thus,  somatose,  mietose,  Ndhrstoff  Hey  den, 
etc.  Reduced  haemoglobin  is  used  under  the  names  hcemogallol  and 
hcemol;  the  latter  also,  with  iodine  and  bromine,  as  iodohcemol  and 
bromhcemoL 

Classification.  This  is  difficult  on  account  of  our  imperfect 
knowledge  as  to  the  size  of  the  molecule,  the  constitution  of  the 
bodies,  etc.  The  following  is  the  generally  accepted  classification,  but 
we  know  of  many  proteids  which  belong  between  these  groups  and 
also  those  which  cannot  be  classified  in  any  of  the  groups:  1.  Simple 
proteids;  2.  Compound  proteids ;  3.  Modified  proteids;  4.  Albuminoid 
or  proteinoid  substances;  5.  Enzymes  or  unorganized  ferments  (it 
has  not  been  positively  proven  that  these  bodies  are  protein  sub- 
stances); 6.  Poisonous  proteids  or  toxalbumins  (more  correctly 
toxo proteins).  Under  the  true,  native,  or  genuine  proteins  we 
understand  those  whose  solutions  coagulate  on  heating  or  by  other 
means  and  which  cannot  be  then  dissolved  without  further  cleavage 
or  without  changing  their  original  properties  but  remain  perma- 
nently changed  (modified). 


I.  Native  or  True  Proteids. 

a.  Albumins. 

They  are  soluble  in  water,  acids,  alkalies;  their  aqueous  solutions 
coagulate  on  warming  when  they  contain  neutral  salts  such  as  NaCl, 
MgSO^.  They  are  precipitated  even  in  the  cold  on  saturating  their 
neutral  solution  with  ammonium  sulphate,  but  not  on  saturating  with 
NaCl,  MgSO,,  or  ZnSO,. 

Ovalbumin  is  precipitated  from  its  solution  by  ether,  coagulates  at 
56°,  is  precipitated  by  excess  of  acids,'  and  is  more  difficult  of  solution 
than  seralbumin. 

Seralbumin  occurs  in  blood  serum,  animal  semen,  chyle,  lymph,  and 
in  all  serous  fluids,  and  in  certain  pathological  urines.  It  is  not  precipi- 
tated by  ether,  coagulates  at  40°-90°,  depending  upon  the  nature  of  the 
solvent,  and  is  precipitated  by  acids  and  readily  soluble  in  an  excess  of  the 
acid. 

Myogen,  muscle  albumin,  the  chief  constituent  of  the  muscle  plasma, 
coagulates  at  40°  or  on  the  death  of  the  muscle. 

Lactalbumin,  milk  albumin,  occurs  in  milk  and  colostrum  and  coagu- 
lates at  72°-84°,  according  to  the  solvent  used. 

Plant  albumins  behave  like  seralbumin. 

Opalisin  is  found  to  a  great  extent  only  in  woman's  milk,  and  is 
characterized  by  its  opalescent  solution. 

Legumelin  occurs  in  the  cereal  grains. 


564  ORGANIC  CHEMISTRY. 


h.  Globulins. 

These  are  insoluble  in  water  but  soluble  in  the  presence  of  neutral 
salts.  It"  these  solutions  are  diluted  with  considerable  water  or  the  salts 
removed  by  dialysis  the  globulins  precipitate  out.  Their  aqueous  solu- 
tions coagulate  on  boiling  and  are  completely  precipitated  in  tlie  cold  by 
saturating  with  (NHJ^SO^,  MgSO^,  or  ZnSO^,  and  incompletely  by  NaCl 
(see  ViteUins). 

Myosin,  muscle  globulin,  is  with  myogen  the  chief  constituent  of 
muscle  plasma.  After  the  death  of  the  muscle  both  coagulate  and  form 
the  rigor  mortis.  Myosin  coagulates  at  50"^.  Myosin -like  bodies  also 
occur  in  many  plants. 

Ssrglobulin,  blood  casein,  paraglobulin,  fibrinoplastic  substance,  oc- 
curs in  blood  serum,  chyle,  lymph,  and  nearly  all  fresh  transudates;  also 
in  albuminous  urine  besides  seralbumin.  Its  neutral  solutions  coagu- 
late at  72°-75°. 

Colostrum  globulin  occurs  in  colostrum. 

Fibrinogen,  metaglobulin,  is  contained  in  all  animal  fluids  which 
either  coagulate  spontaneously  on  standing  (fibrin  formation,  p.  567) 
or  after  the  addition  of  a  few  drops  of  the  fluid  expressed  from  some 
freshly  coagulated  blood.  It  coagulates  on  warming  its  neutral  solution 
to  53°-56°. 

Fibrin  globulin  is  produced  from  fibrinogen  besides  fibrin  in  its  coagu- 
lation and  also  in  the  digestion  of  fibrin. 

2.  Compound  Proteids. 

These  split  into  simple  proteids  and  other  organic  compounds. 
a.  Nucleoproteids. 

On  cleavage  these  yield  proteids  and  acids  of  unknown  constitution 
called  nucleic  acids  (CagH^gNgPgOaa,  etc.),  which  on  boiling  with  dilute 
acids  or  alkalies  yield  phosphoric  acid,  besides  adenine,  guanine,  hypoxan- 
thine,  and  xanthme  (p.  415),  and  these  are  therefore  called  nuclein  bases. 

Nucleins,  compounds  of  nucleic  acid  with  proteid,  also  contain  iron 
and  occur  in  the  cell  nucleus  of  animals  and  plants  and  are  separated  from 
the  nucleoalbumins  on  digestion  with  pepsin-hydrochloric  acid  (p.  568). 
They  behave  like  acids,  are  only  slightly  soluble  or  insoluble  in  water, 
dilute  mineral  acids,  and  neutral  salt  solutions,  but,  on  the  contrary, 
are  readily  soluble  in  di-ute  caustic  alkalies,  Nucleins  occurring  in  fish 
sperm  can  be  split  into  nucleic  acids  and  protamins  (p.  561). 

Nucleoalbumins,  compounds  of  nucleins  with  proteid,  occur  in  the  cell 
nucleus,  often  also  in  the  protoplasm  and  in  animal  flu'ds,  and  leave  nucleins 
on  peptic  digestion,  and  decompose,  on  standing  with  alkalies  or  acids,  in  the 
cold  into  albuminates  or  acid  albumins  (p.  568) .  According  as  to  the  length 
of  time  they  are  exposed  to  the  alkalies  or  acids  they  are  solit  into  nu^'leins, 
nucleic  acids,  or  their  constituents.  They  behave'  like  acids  and  dissolve 
in  dilute  caustic  alkalies  and  decompose,  in  contradistinction  to  the 
nucleins,  on  heating  their  neutral  solutions,  with  the  separation  of  proteid. 

To  this  class  also  belongs  nucleohiston,  which  occurs  in  all  cell  nuclei  an  I 
which  readily  splits  into  a  proteose-like  body,  histon,  and  into  leuconuclein. 
The  nucleic  acid  of  this  latter  body  also  occurs  in  the  thymus  gland,  and 


COMPOUND  PRO  TEWS.  565 

hence  is  called  thymus  nucleic  acid  or  adenylic  add,  and  yields  on  further 
cleavage  thymic  acid  and  then  thymin  (p.  542). 

b.  Paranucleoproteids. 

These  on  cleavage  yield  proteid  and  acids  of  unknown  composition 
called  para  or  pseudo  nucleic  acids  (CijIlgsNaPgO^gj  etc.)-  On  boiling  tlie 
paranucleic  acids  with  alkalies  or  dilute  acids,  phosphoric  acid,  proteid, 
etc.,  but  no  nuclein  bases,  are  produced. 

Paranucleins,  compounds  of  paranucleic  acid  with  proteid,  also  con- 
tain iron  and  are  formed  from  the  paranucleoalbumins  in  their  peptic 
digestion. 

Paranucleoalbumins,  compounds  of  paranucleins  with  proteids.  They 
form  tlie  chief  constituent  of  protoplasm  and  also  occur  in  secretions,  etc. 
They  behave  like  acids  and  are  insoluble  in  water  but  dissolve  in  the 
presence  of  traces  of  caustic  alkalies.  Their  neutral  solutions  do  not 
coagulate  on  boiling,  are  incompletely  precipitated  by  NaCl  and  com- 
pletely by  MgSO^.  On  standing  with  alkalies  or  acids  in  the  cold  the 
paranucleoalbumins  decompose  in  an  ana  ogous  manner  to  nucleoalbu- 
mins  (which  see).  To  this  group  belong  the  mucin  of  ox  bile,  ichthulin 
in  the  carp  eggs,  and  helicoproteid  in  Helix  pomata.  These  latter  split  into 
paranuclein  and  sugar  (p.  5G6,  d). 

The  most  important  paranucleoalbumins  are  the  caseins.  They  are 
precipitated  from  their  solutions  by  heating  to  130°-150°  and  also  at 
ordinary  temperatures  by  certain  ferments  as  well  as  by  the  careful  addi- 
tion of  acids.  The  casein  precipitated  by  rennin  is  different  from  that 
in  solution  or  that  precipitated  by  acids.  Cheese  is  a  putrefactive  product 
of  casein. 

Milk  casein  in  the  milk  of  all  mammals  can  be  precipitated  by  rennin, 
acids,  and  saturation  with  MgSO^.  If  a  few  drops  of  acid  or  some  rennin 
is  added  to  milk  all  the  casein  separates  out  immediately  and  at  the  same 
time  the  fat  is  carried  with  it  (curdled  milk).  In  the  solution  we  have 
milk-sugar,  albumin,  and  the  salts.  This  solution  is  called  sweet  whey.  If 
milk  is  allowed  to  stand  for  a  long  time  it  also  coagulates,  due  to  the  for- 
mation of  lactic  acid  from  the  milk-sugar.  The  filtrate  from  this  curd 
is  called  acid  whey. 

The  vitellins  occur  as  ovovitellin  in  the  yolk  of  the  egg,  as  a  and  ^ 
crystallin  in  the  crystalline  lens,  also  as  phytovitellins  (phytoglobulins)  in 
plants,  and  also  as  conglutin,  legumin,  vicilin,  artolin,  etc.  Thyreoglobulin, 
the  iodized  vitellin  of  the  thyroid  gland,  splits  with  acids  into  thyroiodine 
or  iodothyrin,  which  does  not  belong  to  the  proteids. 

The  iedthalbumins  are  compounds  of  lecithins  (p.  434)  with  vitellins 
and  other  paranucleoalbumins  and  are  found  in  the  mucous  membrane 
of  the  stomach  and  in  the  kidneys,  etc. 

-  c.  Chromoproteids. 

They  are  readily  decomposed  into  proteid  and  a  ferruginous  pigment 
haemochromogen,  which  in  the  presence  of  oxygen  is  oxidized  to  hsematin 
(p.  545).  They  are  soluble  in  water  and  salt  solutions  and  on  heating 
thei?  solutions  we  obtain,  even  below  the  boiling-point,  a  brown  precipi- 
tate of  coagulated  proteid  and  haematin.  Alcohol,  alkalies,  or  acids  (even 
'^'Og)  produce  this  cleavage  even  in  the  cold. 


566  ORGANIC  CHEMISTRY, 

Oxyhaemoglobin,  the  pigment  of  arterial  blood,  forms  with  haemo- 
globin the  chief  constituent  of  the  red  corpuscles.  Both  are  also  found 
to  a  slight  extent  in  certain  muscles  of  mammals  and  in  the  muscles  and 
in  the  blood  of  certain  invertebrates.  It  is  obtained  from  the  blood  cor- 
puscles and  forms  microscopic  crystals  which  are  soluble  in  water  with  a 
blood-red  color. 

If  a  solution  of  oxyhaemoglobin  or  arterial  blood  is  placed  before  the 
spectroscope  we  obtain,  even  when  very  dilute,  a  characteristic  absorp- 
tion spectrum  consisting  of  two  absorption  bands.  If  a  small  quantity  of 
a  reducing  agent  (ammonium  sulphide  or  an  ammoniacal  solution  of 
ferro-tartrate)  is  added  to  an  oxyhaemoglobin  or  blood  solution  the  color 
becomes  darker  and  the  two  characteristic  absorption  bands  of  oxyhaemo- 
globin disappear  and  the  characteristic  one-banded  spectrum  of  haemo- 
globin takes  their  place.  The  band  is  broader  than  the  other  two  and  on 
shaking  the  reduced  solution  with  air  or  oxygen  the  two  oxyhaemoglobin 
bands  appear  again.  Carbon  monoxide  haemoglobin  gives  two  absorption 
bands  similar  to  the  oxyhaemoglobin  bands,  but  they  are  not  removed  by 
reducing  agents  (p.  189). 

Haemoglobin,  the  pigment  of  venous  blood  (other  occurrence  see 
above),  forms  red  plates  or  prisms  which  when  dissolved  give  one  character- 
istic absorption  band  (see  above).  With  acids  or  bases  it  splits  into 
proteid  and  haemochromogen.  With  H^S,  COg,  CO,  NO,  HCN,  and  CjHa 
it  gives  crystalline  compounds  which  are  isomorphous  with  oxyhaemoglobin. 
If  these  gases  are  passed  through  an  oxyhaemoglobin  solution  or  blood 
they  expel  the  oxygen  and  combine  with  the  haemoglobin.  If  oxygen  is 
again  passed  through  these  compounds  only  the  carbon  dioxide  haemoglo- 
bin is  converted  into  oxyhaemoglobin,  the  other  compounds  remaining 
unchanged.  For  this  reason  these  gases  have  a  poisonous  action,  as  they 
make  the  haemoglobin  incapable  of  carrying  the  oxygen  necessary  for 
the  organism. 

Methaemoglobin,  isomer  of  oxyhaemoglobin,  is  a  transformation  prod- 
uct of  the  oxyhaemoglobin,  from  which  it  is  produced  by  the  action  of 
KMnO^,  pyrogallic  acid,  potassium  ferricyanide,  etc.  It  is  sometimes 
found  in  pathological  fluids,  as  well  as  in  urine  and  blood  after  poisoning, 
and  forms  brownish-red  crystals.  The  absorption  spectrum  of  the  watery 
or  acidified  solution  is  similar  to  that  of  haematin  m  acid  solution,  but  is 
readily  differentiated  by  the  fact  that  the  addition  of  alkali  and  a  reducing 
substance  converts  it  into  the  spectrum  of  haemochromogen. 

d.  Glycoproteids. 

These  split  into  proteid  and  carbohydrate. 

Mucins  are  the  substances  precipitated  from  their  colloidal  solutions  by 
acetic  acid,  which  are  insoluble  in  an  excess  of  the  acetic  acid  (in  contra- 
distinction to  all  other  proteid  substances  and  the  mucoids).  On  heating, 
with  dilute  mineral  acids  they  yield  proteid  and  a  carbohydrate  which 
reduces  alkaline  solutions  of  copper.  They  occur  in  many  secretions  and 
excretions  (human  bile,  saliva,  mucus,  synovial  fluid,  feces,  urine,  etc.), 
in  the  connective  tissue  as  well  as  in  all  the  organs  composed  chiefly 
of  cells  (glands,  etc.).  In  the  lower  animals  we  do  not  find  mucins  but 
mucinogens,  which  are  split  into  mucins  and  proteid  substances  by  bases. 
The  various  mucins  are  called  snail  mucin,  tendon  mucin,  and  submax- 
illary mu^n. 


MODIFIED  PRO  TEWS.  567 

Muciods,  mucinoids,  are  the  mucuos  bodies  not  precipitated  by  acetic 
acid  and  occur  as  pseudomucin  (para  or  meta  albumin)  in  ascitic  and 
ovarial  cystic  fluids,  collomucoid  in  cancerous  growths,  ovomucoid  in  the 
egg,  toxomucoid  (p.  572)  from  cultures  of  the  tubercle  bacillus.  Chon- 
dromucoid,  contained  in  the  cartilaginous  tissues,  is  a  compound  of  pro- 
teid  with  chondroitin  sulphuric  acid,  CisHgyNSOi,,  which  spUts  further  into 
chondroitin  and  sulphuric  acid.      Animal  amyloid  is  also  a  compound  of 

f)roteid  with  chondroitin-sulphuric  acid  and  is  found  in  milk  and  patho- 
ogically  in  various  organs.  It  differs  from  other  proteids  in  giving  a 
icd  color  with  iodine  solutions  and  a  violet  to  blue  color  with  iodine 
solution  and  sulphuric  acid,  hence  its  name. 

Hyalogens  is  the  name  given  to  a  series  of  very  widely  distributed 
bodies  found  in  the  skeleton  tissues  of  lower  animals.  They  have  been 
little  studied  and  decompose  by  bases  into  a  proteid-like  body,  and  into 
hyalins  containing  nitrogen  and  closely  related  to  the  carbohydrates. 

The  hyalin,  chondroitin,  C]8H27NOi4,  decomposes  on  boiling  with 
dilute  acids  into  acetic  acid  and  chondrosin,  CiaHaiNOij;  this  last  splits  into 
glycuronic  acid  and  glucosamine  (p.  457, 6);  the  hyalin  chitin,  Ci^HgoNaOij, 
sphts  into  acetic  acid  and  chitosan,  Cj^HgeNgOn;  and  this  further  yields 
acetic  acid  and  glucosamine. 

3.  Modified  Proteids. 

These  are  formed  from  the  native  proteids  by  the  action  of  heat, 
ferments,  or  chemical  agents  and  have  other  properties  from  their  mother- 
substances  and  are  not  reconvertible  into  them. 

Coagulated  proteids  are  produced  on  heating  their  neutral  or  faintly 
acid  solutions  or  by  the  action  of  certain  ferments..  They  are  insoluble 
in  water,  dilute  acids,  and  alkalies.  They  form  when  dry  colorless  or 
yellowish  hard  masses. 

Animal  fibrin  forms  in  liquids  containing  fibrinogen  when  these  are 
removed  from  the  influence  of  the  living  normal  vessel  walls  (drawn 
blood).  The  fibrinogen  on  the  exit  of  its  solution  (of  blood)  from  the 
animal  body  is  converted  into  fibrin  and  fibringlobulin  by  the  fibrin 
ferment  which  is  produced  on  the  destruction  of  the  white  blood-corpuscles. 
Fibrin  is  insoluble  in  water  and  salt  solutions,  swells  up  in  NaCl  solution, 
in  dilute  acids  and  alkalies,  without  dissolving  therein.  It  forms  when 
moist  a  white  amorphous,  elastic  mass  which  on  warming  to  75°  or  by 
alcohol  becomes  hard  and  brittle. 

Myogen  fibrin  and  myosin  fibrin  are  the  solid  proteids  formed  from 
myogen  and  myosin,  caused  by  a  myosin  ferment. 

Plant  fibrin,  gluten,  occurs  in  the  plant  seeds,  especially  the  cereal 
grains,  and  is  obtained  by  kneading  the  seeds  with  water,  when  the  plant 
albumins  and  ^arch  granules  are  washed  out  and  the  gluten  remains  as  a 
sticky,  tough  mass,  which  when  dry  forms  a  yellow  powder  called  aleuro- 
nate  (p.  563),  Like  anmal  fibrin  it  docs  not  seem  to  be  preformed  and 
it  is  probably  derived  from  the  plant  globulins  in  the  presence  of  water 
by  a  ferment  which  has  not  been  isolated.  Plant  fibrin  is  a  mixture  of  a 
proteid  called  artolin  with  a  not  closely  studied  body  containing  phos- 
phorus and  calcium.  Such  mixtures  are  the  proteids  gluten  casein,  gluten 
fibrin,  gliadin,  and  mucedin  which  used  to  be  considered  as  constituents  of 
gluten.  The  solubility  in  60  per  cent,  alcohol  is  characteristic  of  plant 
fibrin. 


568  ORGANIC  CHEMISTRY. 

Acid  albumins  (syntonins)  and  alkali  albuminates  (albuminates) 
are  produced  by  the  action  of  acids  or  bases  upon  proteids  and  form 
gelatmous  compounds  which  are  insoluble  in  water  and  soluble  in  dilute 
acids  and  alkalies.  Their  solutions  do  not  coagulate  on  boiling  but  are 
precipitated  on  neutralization  and  by  saturating  with  neutral  salts  By 
the  action  of  bases  a  splitting  off  of  nitrogen  as  ammonia  takes  places  as 
well  as  a  removal  of  sulphur. 

Proteoses,  hemialbumoses,  albumoses,  propeptones,  are  the  intermedi- 
ary products  soluble  in  water,  obtained  in  digestion  between  the  proteids 
and  the  peptones.  Just  as  the  starches  pass  through  a  series  of  dextrins 
be  ore  sugar  is  produced,  so  the  passage  of  the  proteids  into  peptones 
takes  place  through  the  formation  of  proteoses,  which  in  properties  deviate 
more  and  more  from  the  original  proteid.  They  are  sometimes  found 
in  the  urine  in  osteomalacia  and  give  the  biuret  test  (p.  562,  d)  even 
in  the  cold.  Their  solutions  do  not  coagulate  on  boiling.  The  primary 
proteoses  {proto-,  hetero-,  dys-proteoses)  are  produced  first  from  the  pro- 
teids and  are  precipitated  by  copper  sulphate,  nitric  acid,  by  acetic  acid 
and  potassium  ferrocyanide,  these  precipitates  disappearing  on  warming 
and  reappearing  again  on  cooling.  Their  neutral  solutions  are  completely 
precipitated  by  an  equal  volume  of  a  saturated  ammonium  sulphate - 
solution. 

Secondary  proteoses  (deuteroproteoses)  are  formed  from  the  primary 
proteoses  and  pass  directly  into  peptones.  They  are  not  precipitated 
by  CuSO^,  HNO3,  K4FeCbNe+C2H^02,  but  on  the  contrary  are  precipi- 
tated on  saturating  their  solution  with  powdered  ammonium  sulphate. 

Peptones.  All  proteids,  with  the  exception  of  amyloid,  metalbumin, 
nucleins,  paranucleins,  and  keratins,  are  transformed  by  pepsin  or  trypsin 
(p.  570)  into  peptones  The  proteids  also  yield  peptones  beside  other 
products  by  putrefaction  and  by  treatment  with  strong  acids  or  bases. 
The  formation  of  peptones  is  always  an  intermediary  stage  to  the  forma- 
tion of  leucin,  tyrosin,  and  other  amido  acids.  The  formation  of  peptone 
from  other  proteids  depends  upon  the  taking  up  of  water  by  the  proteid 
molecule.  Carnic  add,  CioH^N^Og,  a  cleavage  product  of  phosphocarnic 
acid,  which  is  a  nucleon,  i.e.,  a  nuclein-like  substance,  is  a  crystalline 
peptone  free  from  sulphur,  in  contradistinction  to  other  peptones. 

The  peptones  differ  from  all  other  proteid  bodies  by  the  following 
reactions:  a.  They  are  diffusible  (p.  46)  through  vegetable  and  animal 
membranes,  b.  They  are  soluble  in  water  in  every  proportion,  the 
solution  does  not  coagulate  on  boiling  (see  Proteoses),  c.  They  are  not 
precipitated  from  their  solutions  by  either  acetic  acid  and  potassium 
ferrocyanide,  nor  by  acids  or  alkalies,  nor  by  acetic  acid  and  neutral  salts, 
nor  on  saturation  with  ammonium  sulphate.  By  this  last  method  or 
by  boiling  with  ferric  acetate  in  faintly  acetic  acid  solution  all  proteids 
may  be  separated  from  the  peptones,  d.  Peptones  are  detected  in  solu- 
tions free  from  other  proteids  by  means  of  the  biuret  test  (p.  562,  d),  and 
their  precipitation  by  tannic  acid,  phosphomolybdic  acid,  phosphotungstic 
acid.  Mercury  peptone  solution,  iron  peptone,  iron-manganese  peptone, 
obtained  by  the  action  of  the  respective  metallic  salts  upon  peptone 
£olutions,  are  used  in  medicine. 


ALBUMINOIDS.  569 


4.  Albuminoids 

are  nitrogenous  constituents  of  the  animal  body  which  are  related  to  the 
proteids  not  only  by  their  elementary  composition  but  also  by  the  corre- 
spondence of  many  react'ons.  They  occur  mostly  undissolved  as  an 
integrate  constituent  of  tissues  and  are  characterized  by  their  resistance 
to  chemical  agents. 

Collagen,  gelatine-yielding  substance,  forms  the  chief  constituent  of 
the  connective  fibres  and  organic  substance  of  the  bony  tissue  (called 
ossein) ;  also  mixed  with  other  substances  forms  the  ground  substance  of 
cartilage  which  was  formerly  considered  as  a  special  body  and  which 
was  called  chondrin  or  chondringen.  Collagen  is  insoluble  in  water  salt 
solutions,  dilute  acids,  alkalies,  and  on  boiling  with  water  it  is  converted 
into  gelatine.  The  gelatine-forming  tissues  combine  with  tannic  acid, 
alum,  or  fats  and  then  when  dry  form  a  pliable  tissue  which  does  not 
undergo  putrefaction.     Tissues  thus  changed  are  called  leather. 

Gelatine,  glutin,  glue,  is  produced  on  boihng  the  collagens  v/ith  water 
and  when  pure  is  a  colorless,  transparent  amorphous  mass  which  is  soluble 
in  hot  water:  On  cooling  this  solution  it  solidifies  to  a  gelatinous  mass; 
if  the  boiling  is  continued  too  long,  the  gelatine  loses  its  property  of  gelatin- 
izing and  is  converted  into  so-called  gelatine  peptone.  Gelatine  is  soluble  in 
the  cold  in  dilute  acetic  acid,  other  acids,  and  in  alkalies,  and  is  not  precipi- 
tated from  its  solutions  by  acids,  basic  lead  acetate,  alum,  while  it  is  pre- 
cipitated by  tannic  acid'  or  alcohol.  On  boiling  with  dilute  sulphuric 
acid  we  obtain  glycocoll  and  leucin.  When  impure  it  is  called  glue  and 
is  prepared  from  animal  hides  which  are  free  from  fat,  blood,  etc.,  and 
softened.     The  best  forms  of  gelatine  are  prepared  from  calves'  feet. 

Keratin,  horn  substance,  is  the  chief  constituent  of  whale-bone,  of 
horn  tissue,  epidermis,  nails  (hoofs  and  claws),  hair  (feathers,  quills, 
tortoise-shell),  horns.  If  these  are  finely  powdered  and  treated  consecu- 
tively with  water,  alcohol,  ether,  and  pepsin  hydrochloric  acid  a  body 
having  variable  composition  remains  behind  which  has  been  called  keratin. 
Keratin  does  not  putrefy  and  burns  with  a  characteristic  odor,  dissolves 
in  caustic  alkalies,  ammonia,  and  boiUng  acetic  acid.  The  sulphur  of  the 
keratin  is  in  part  loosely  combined,  hence  tissue  containing  keratin  becomes 
black  by  lead  and  silver  salts  by  forming  their  sulphides  (hair-dyeing 
agents).     Horn  shavings  develop  HgS  when  moist. 

Glutolin,  from  its  behavior/  stands  between  proteids  and  the  albumin- 
oids, occurs  in  blood  serum. 

Elastin  forms  the  elastic  tissue  occurring  in  higher  animals,  espe- 
cially in  the  connective  tissue.  It  retains  the  structure  of  the  material 
used  in  its  preparation.  It  is  yellowish-white  and  very  elastic  when  moist. 
It  contains  its  sulphur  so  loosely  combined  that  it  was  formerly  considered 
free  from  sulphur. 

Spongin  forms  the  chief  mass  of  sponges. 

Conchiolin  occurs  in  the  shells  of  musse's. 

Fibroin  and  sericin  are  the  two  chief  constituents  of  raw  silk.  On 
boiling  with  dilute  acids,  fibroin  yields  glycocoll  and  considerable  tyrosin, 
while  sericin  yields  leucin  and  crystalline  serine  (p.  407), 

Cornein  forms  the  organic  substance  of  the  corals. 


570  ORGANIC  CHEMISTRY. 


5.  Enzymes. 


The  unorganized  ferments  or  enzymes  (p.  54)  all  appear  to  be  pro^ 
teid-like  compounds,  as  they  give  nearly  all  the  reactions  for  the  proteids; 
still  it  is  possible  that  the  enzymes  attach  themselves  to  the  proteids 
on  being  precipitated  and  their  separation  not  being  perfect  on  purifica- 
tion. They  are  readily  soluble  in  faintly  acid  or  alkaline  water  as  well  as 
in  glycerine.  They  are  colorless,  powderous  bodies  which  are  not  prec  pi- 
tated  from  their  solutions  on  boiling  but  are  precipitated  by  alcohol. 
Their  solutions  lose  their  activity  generally  at  60°  and  some  at  100°,  but 
when  dry 'many  may  be  heated  above  100°  without  losing  their  activity. 
They  are  generally  obtained  by  extracting  the  substances  containing 
them  with  glycerine  and  precipitating  the  extract  with  alcohol.  Their 
maximum  activity  lies  generally  between  35°  and  45°. 

a.  Proteid-digesting  or  Proteolytic  Enzymes. 

Ingluvin  is  the  pepsin-like  ferment  of  the  hen's  gizzard. 

Pepsin,  the  proteolytic  ferment  of  the  gastric  juice,  fo.ms  a  white 
powder  which  is  only  active  in  faintly  acid  solution. 

Papain,  papayotin,  in  the  juice  of  the  Carica  papaya,  is  most  active 
in  laintly  alkaline  liquids. 

Proteolytic  enzvmes  are  also  found  in  yeast  and  other  fungi. 

Trypsin,  pancreatin,  occurs  in  the  pancreas  and  is  most  active  in 
faintly  alkaline  solutions. 

b.  Polysaccharide-splitting  Enzymes. 

They  are  a'so  called  d'astatic,  saccharifying,  pmylolytic  ferments  on 
account  of  their  transforming  starch,  etc.,  into  sugars. 

Diastases,  amylases,  have  the  power  of  converting  starches  into 
dextrins  and  maltose  (p.  354).  They  are  found  rather  widely  distributed 
in  the  higher  and  lower  plan  s  (plant  diastases),  also  in  the  animal  king- 
dom (animal  diastases),  chiefly  in  the  pancreas  (amylopsin),  in  the  saliva 
(ptyalin),  to  a  slight  extent  in  the  liver,  bile,  blood,  chyle,  brain,  the  kid- 
neys, stomach,  and  intestinal  mucosa. 

Inulass  splits  inuHn  (p.  459)  into  laevulose  and  is  found  in  many  plants 
instead  of  diastase. 

Cellulase  splits  cellulose  into  hexoses  and  pentoses,  is  found  in  many 
germinating  plants  and  also  in  the  animal  kingdom. 

c.  Disaccharide-s putting  Enzymes. 

Invertase,  sucrase,  invertin,  is  contained  in  many  plants  and  extracta- 
ble  from  yeast  by  water.  It  splits  cane-sugar  into  dextrose  and  laevulose. 
A  similar  enzyme  is  found  in  the  intestinal  contents 

Glucase,  found  in  malt  and  splits  maltose  (p.  455). 

Maltase  occurs  in  certain  varieties  of  yeast  and  inverts  maltose 
(p.  455). 

Lactase,  found  in  the  Saccharomyces  kefir  and  Tryocola  splits  lactose 
into  dextrose  and  galactose  (p.  455). 

Trehalase  occurs  in  the  Asperigillus  niger,  and  splits  trehalose  (p.  455). 


ENZYMES.  571 

d.  Monosaccharide-splitting  Enzymes. 

Zymase,  alcoholase,  contained  in  the  fluid  pressed  from  previously- 
destroyed  yeast-cells,  produces  alcoholic  fermentation  (p.  354).  Similar 
enzymes  to  zymase  have  also  been  found  in  animal  cells. 

e.  Glucoside-splitting  Enzymes. 

Emulsin,  synaptase,  of  the  sweet  and  bitter  almond,  splits  the  gluco- 
sides  amygdaUn  and  salicin. 

Myrosin,  of  the  white  and  black  mustard-seed,  splits  the  glucoside 
potassium  myronate  (p.  438). 

/.  Glyceride-spliUing  Enzymes. 

Lipase,  steapsin,  steaptase,  occurs  in  the  pancreas  of  all  camivora  as 
well  as  in  certain  plants. 

g.  Coagulating  Enzymes. 

Rennin,  chymosin,  coagulates  neutral  casein  solutions,  occurs  in  the 
gastric  juice  of  the  calf  and  sheep,  A  similar  enzyme  is  also  found  in 
various  varieties  of  Fiscus  and  oiher  plants. 

Fibrin  ferment,  thrombin,  thrombase,  converts  fibrinogen  into  fibrin 
(p.  567)  in  the  presence  of  neutral  salts. 

Gluten  ferment  (?)  converts  the  proteids  of  flour  into  gluten  (p.  567). 

Pictase,  which  converts  the  expressed  juice  of  many  fruits  into  a  jelly. 

h.  Oxidizing  Enzymes  or  Oxidases. 

These  seem  to  be  a  mixture  of  peroxidases  which  only  oxidize  in 
the  presence  of  peroxides  and  oxygenases,  the  latter  oxidizing  only  in  the 
presence  of  oxygen. 

Laccase,  in  the  juice  of  the  Japanese  lac-tree,  and  oxidases  related  to 
this  also  occur  in  many  plants. 

Tyrosinase,  in  many  fungi,  in  the  dahlia  and  potato  tubers,  beets, 
etc.,  oxidizes  tyrosin  but  al  o  many  other  cyclic  compounds. 

i.  Amide-splitting  Enzymes 

occur  in  fungi  which  cause  the  fermentation  of  urine  (splitting  the  urea, 
p.  410). 

y.  Reducing  Enzymes, 

also  called  reductases,  cause  reduction  processes  and  are  found  especially 
in  the  plants. 

CataJase  is  the  name  of  the  enzyme  which  sets  molecular  oxygen  free 
from  peroxides. 

6.  Toxalbumins. 

In  various  plants  and  animals  we  find  bodies  which  in  regard  to  behav- 
ior belong  on  one  side  to  the  food-proteids  and  on  the  other  side  to  tha 
enzymes,  but  they  are  more  or  less  poisonous.  In  certain  cases  their 
poisonous  action  is  due  to  toxins  which  cannot  be  separated  from  the 
proteids  by  the  methods  used. 


572  ORGANIC  CHEMISTRY. 

Of  those  to  be  mentioned  we  have  ahrin  of  the  jequirity  bean,  crotin  in 
theCrotonTiglium,ncm  in  the  castor-seed,  lupinotoxin  in  certain  varieties 
of  lupines,  sapotoxin  in  soap  and  Senegal  roots,  snake  poisons,  and  the 
poison  of  spiders,  and  certain  fishes,  etc. 

Toxalbumins  may  also  be  obtained  from  the  pure  cultures  of  patho- 
genic bacteria  and  also  from  those  yielding  toxins;  thus,  from  diphtheria, 
anthrax,  typhoid,  and  tetanus  cultures,  and  tuberculin  and  tuberculocidin 
from  the  tubercle  bacilli,  and  anticholerin  from  cholera  bacilli,  mallein 
from  glanders  bacilli,  peptotoxines  produced  in  digestion,  and  toxomiLCoid 
(p.  567),  etc. 


INDEX. 


a=ana,  540 
a = asymmetric,  469 
a  =  compounds,  467,  538 
Abietic  acid,  525 
Abrastol,  515 
Abraum  salts,  202 
Abrin,  572 
Absinthin,  527 
Absinthole,  524 
Absorption,  50 
Absorption  spectrum,  45 
Accumulators,  260 
Acenaphthene,  515 
Acetal,  351,  401 
Acetaldehyde,  359 
Acetamide,  367 
Acetanilide,  485 
Acetates,  363 
Acetic  acid,  361 

chlorinated,  368 

ethyl  ester,  364 

—  anhydride,  367 

—  ether,  364 
Acetphenetidine,  485 
Acetoacetic  acid,  364 

—  ester,  365 
Acetone,  371 
Acetonitrile,  390 
Acetophenone,  498 
Acetopyrine,  551 
Acetoximes,  372 
Acetylene,  441 

—  copper,  442 

—  silver,  442 
Acetyl  acetic  acid,  364 

—  chloride,  367 

—  formic  acid,  403 

—  phenylendiamine,  468 


Acetyl  phenetidine,  485 

—  propionic  acid,  371 

—  oxide,  367 

—  salicylic  acid,  493 

—  succinic  acid,  366 
Achillein,  559 
Achilletine,  559 
Achroo dextrin,  459 
Acid  albumin,  568 

—  amides,  336 

—  anhydrides,  98,  336,   345,   367, 

404 

—  chlorides,  160 

—  chloranhydrides,  160 

—  esters,  332 

—  imides,  336 

—  radicals,  98,  336 
Acids,  84,  97,  335 

—  basicity,  335 

—  dihydric,  monobasic,  335,  403 

—  dibasic,  335,  420 

—  hydric,  98 

—  monobasic,  344 

—  monohydric,  344,  444 

—  organic,  335 

—  oxygen-free,  98 

—  oxy-,  98 

—  valence  of,  98,  335 
Acoin,  486 
Aconine,  558 
Aconitic  acid,  431 
Aconitine,  558 
Acopyrine,  551 
Acoretin,  529 
Acorin,  529 

Acridine  compounds,  540 
Acrolein,  439 
Acrose,  450 

573 


574 


INDEX. 


Acrylic  acid,  440 

Actinium,  272 

Actinometer,  94 

Activity,  optical,  39 

Acyles,  336 

Adamkiewicz's  reaction,  562 

Addition  products,  cyclic,  463 

Adenine,  415 

Adenylic  acid,  565 

Adipic  acid,  420 

Adipocere,  377 

Adonite,  443 

Adurol,  481 

^schynite,  248 

^sculetin,  501 

^sculin,  527 

Affinity,  7,  58 

—  kinetic,  nature  of,  59 

—  and  energy,  7 

—  measure  of,  58 
Agaricic  acid,  529 
Agaricin,  529 
Agate,  195 

Agents,  chemical,  action  on  organic 

compounds,  321 
Aggregation,  state  of,  32 
Air,  analysis  of,  154 

—  atmospheric,  152 

—  mortar,  220 
Airogen,  495 
Airoform,  495 
Airol,  495 
Akagin,  442 
Alabandite,  273 
Alabaster,  222 
Alanin,  371 

Alant  camphor,  524 
Alantole,  524 
Alantol  lactone,  515 
Albacide,  562 
Albuminoids,  569 
Albumins,  563 
Albuminates,  568 
Albumoses,  568 
Alcoholates,  343,  351 
Alcohols,  331 
Alcohol  acids,  477 

—  anhydrides,  332,  404 

—  compounds  with  metals,  381 

—  compounds  with   metalloids, 

377 

—  cyclic,  475 


Alcohols,  dihydric,  329,  399 

—  diprimary,  400 

—  disecondary,  400 

—  ditertiary,  400 

—  hexahydric,  445 

—  isomeric,  333 

—  monohydric,  329,  342 

—  pentahydric,  443 

—  polyhydric,  447 

—  primary,  333 
tertiary,  400 

—  secondary,  334 

—  tertiary,  335 

—  tetrahydric,  443 

—  trihydric,  329,  432 
Alcohol  phenols,  475 

—  radicals,  329 

divalent,  394 

hexavalent,  445 

monovalent,  339,  437 

pentavalent,  443 

polyvalent,  447 

tetravalent,  441 

trivalent,  431 

Aldehydes,  333,  350     . 
Aldehyde  acids,  337 

—  alcohols,  337 

—  resins,  350 
Aldine,  542 
Aldol,  360 

—  condensation,  360 
Aldoses,  337,  402 
Aldoximes,  351 
Aleuronate,  563 
Algarot  powder,  179 
Alicyclic  compounds,  327 
Aliphatic  compounds,  326 
Alizarin,  516 

—  blue,  517 

—  bordeaux,  517 

—  carmine,  517 

—  orange,  517 

—  black,  515 
Alkalies,  201 

Alkali  albuminates,  568 

—  blue,  507 

—  metals,  201 
Alkaline  earths,  218 

—  earth-metals,  218 
Alkali  phenylate,  474 
Alkaloids,  552 
Alkannin,  531 


INDEX. 


575 


Alkanet  red,  531 

Alkarsin,  380 

Alkenes,  394 

Alkenyls,  329 

Alkyl-ammonium  hydroxides,  379 

Alkyls,  329,  339 

Alkyl  cyanides,  390 

Alkylenes,  329,  394 

Alkylene  oxides,  399 

Allantoin,  414 

Allanturic  acid,  413 

Allocinnamic  acid,  500 

Aloes,  525 

Aloin,  517 

Alloisomerism,  303 

Allophanic  acid,  413 

Alsol,  430 

Allotropism,  80 

Alloys,  49 

Alloxan,  414 

AUoxanic  acid,  414 

AJloxanthine,  415 

Allyl,  437 

—  alcohol,  438 

—  aldehyde,  439 

—  aniline,  540 

—  benzene  compounds,  499 

—  compounds,  438 

—  disulphide,  438 

—  iodide,  438 

—  isosulphocyanic  ester,  438 

—  mustard  oil,  438 

—  pyrocatechin  methylene  ether, 

500 

—  sulphide,  438 

—  sulphocyanide,  438 

—  sulphocarbimide,  411 

—  thiourea,  411 
Allylene,  441 
Almond  oil,  436 

Alpha  compounds,  467,  538 
Alpinin,  542 
Alphyles,  471 
Alum,  252 

—  concentrated,  251 

—  cubical,  252  * 

—  earth,  252 

—  neutral,  252 

—  stone,  252 

—  slate,  252 
Alumina,  249 
Aluminite,  251 


Aluminates,  251 

Aluminium,  248 

—  acetate,  363 

—  aceto-tartrate,  430 

—  alkyls,  382 

—  alloys,  249 

—  amalgam,  243 

—  bronze,  249 

—  chloride,  251 

—  detection  of,  254 

—  fluoride,  251 

—  group,  247 

—  hydroxide,  250 

—  oxide,  249 

—  silicates,  252 

—  sulphate,  251 

—  sulphide,  251 

—  tannate-tartrate,  495 
Alunite,  252 

Amalgamation  of  silver,  238 
Amalgams,  242 

Amalic  acid,  415 
Amblygonite,  215 
Amber,  525 
Amethyst,  195 
Amianthus,  227 
Amic  acids,  336,  420 
Amid,  96 

—  bases,  330,  378 

—  derivatives  of  benzene,  483 

—  of  carbonic  acid,  409 
Amides,  336,  367,  420 

—  acid,  336 

—  of  bibasic  acids,  420 
Amidines,  336 
Amido,  96 

—  acetic  acid,  369 

—  acetyl  phenetidin,  485 

—  acids,  336,  369 

—  alcohols,  337 

—  aldehydes,  337 

—  azo  compounds,  510 

—  barbitunc  acid,  419 

—  benzene  compounds,  483 

—  benzoic  acid,  489 

—  caproic  acid,  376 

—  cinnamic  aldehyde,  540 

—  compounds,  cyclic,  483 

—  diphenyl,  504 

—  ethylenlactic  acid,  407 

—  ethyl-sulphonic  acid,  401 

—  glutaric  acid,  425 


576 


INDEX, 


Amido  hydrocoumaric  acid,  502 

—  hypoxanthine,  417 

—  isobutylacetic  acid,  376 

—  ketones,  337 

—  malonylurea,  419 

—  naphthalene,  514 

—  naphthol-sulphonic  acid,  515 

—  oximes,  331 

—  oxybenzoic    acid-methyl    ester, 

493 

—  oxypurin,  416 

—  phenols,  479 

—  phenylacetic  acid,  46S 

—  phenylacetyl  salicylate,  492 

—  propionic  acid,  371 

—  purin,  415 

—  pyrotartaric  acid,  425 

—  succinic  acid,  424 

—  succinamic  acid,  425 

—  sugars,  450 

—  toluenes,  487 
Amidol,  491 
Amidulin,  459 
Amimides,  336 
Amin  bases,  330,  377 
Amines,  330,  377 

—  mixed,  378 
Amino  =  amido 
Amino  acids,  336,  420 
Aminoform,  398 
Ammonia,  147 

—  detection  of,  150 
Ammonia-soda  process,  214 
Ammonium,  150,  216 

—  acetate,  363 

—  acid  oxalate,  423 

—  alum,  252 

—  amalgam,  216 

—  bases,  331,  379 

—  bicarbonate,  218 

—  bromide,  217 

—  carbamate,  409 

—  carbonate,  218 

—  chloride,  216 

—  cyanate,  392 

—  compounds,  216 

—  detection  of,  218 

—  formate,  353 

—  hydrocarbonate,  218 

—  hydroxide,  216 

—  hydrosulphide,  216 

—  hydroxalate,  423 


Ammonium  iodide,  217 

—  iridium  chloride,  292 

—  iron  alum,  284 

—  magnesium  phosphate,  230 

—  magnesium  sulphate,  229 

—  molybdate,  271 

—  nitrate,  217 

—  nitrite,  217 

—  oxalate,  423 

—  oxide,  216 

—  peroxide,  216 

—  persulphate,  217 

—  platinum  chloride,  292 

—  phosphate,  217 

—  phosphomolybdate,  169 

—  salts,  150 

—  sodium  phosphate,  217 

—  sulphydrate,  216 

—  sulphate,  217 

—  sulphide,  216 

—  sulphoarsenate,  177 

—  sulphocyanide,  393 

—  thiocyanate,  393 

—  sulphostannate,  25S 
Ammoniacal  liquor,  148 
Ammoniacum  gum,  525 
Amorphous,  34 
Amygdalin,  498 
Amygdalic  acid,  498 
Amylase,  570 

Amyl  acetate,  374 

—  alcohols,  374 

—  benzene,  472 

—  esterl  374 

—  nitrite,  374 

—  sulphuric  acid,  375 

—  valeriate,  374 
Amyloid,  457 
Amylodextrin,  459 
Amylopsin,  570 
Amylum,  453  , 
Amyrin,  526 

Ana,  540 
Ana^sthesin,  489 
Analysis,  electrolytic,  76 

—  of  the  air,  1 54 

—  organic,  calculation  of,  312 

—  organic,  qualitative,  309 

—  organic,  quantitative,  311 
Analytical  chemistry,  2 

determination  of  the  consti 

tution  by,  317 


INDEX. 


577 


Anatase,  262 

Andalusite,  248 

Anethol,  499 

Angelic  acid,  440 

Angelicin,  529 

Anglesite,  259 

Anhdyrides,  98,  99,  332,  336 

—  of  the  lactic-acid  series,  404 
Anhydrite,  222 

Anhydro  acids,  197 
Anilides,  485 
Anilido-acetic  acid,  547 
Anilido-malonic  acid,  547 
Anilido-quinone,  485 
Anilines,  484 
Aniline,  484 

—  acetate,  485 

—  black,  543 

—  blue;  507 

—  dyes,  484,  506 

—  oil,  507 

—  red,  507 

—  salts,  484 

—  yellow,  510 
Animal  cellulose,  457 

—  charcoal,  187 

—  fibrin,  567 

—  oil,  538 
Anion,  75 

Anis  camphor,  499 
Anisic  acid,  493 

—  aldehyde,  493 
Anisidines,  485 
Anis  oil,  521 
Anisoin,  488 
Anisol,  480 
Anisyl  alcohol,  493 
Anode,  75 
Anthocyanin,  531 
Anthoxanthine,  531 
Anthracene,  515 

—  dyes,  517 

—  green,  50S 

—  oil,  473 
Anthracine,  398 
Anthranilic  acid,  489 
Anthrapurpurin,  517 
Anthraquinoline,  537 
Anthraquinone,  516 

—  sulphonic  acid,  516 
Anthracite  coal,  188 
Antibenzaldoxime,  309 


Anticholerin,  572 
Antichlor,  211 
Antifebrine,  485 
Anti-forms,  309 
Antimonic  acids,  180 

—  anhydride,  180 

—  chloride,  179 
Antimonous  acid,  180 

—  anhydride,  180 

—  chloride,  179 
Antimony,  177 

—  alloys,  178 

—  butter  of,  179 

—  chloride,  179 

—  compounds,  178 

—  detection  of,  181 

—  glance,  177 

—  hydride,  178 

—  mirror,  178 

—  oxides,  179 

—  oxychloride,  179 

—  oxysulphide,  181 

—  pentachloride,  179 

—  pentoxide,  180 

—  silver,  179 

—  sulpho-acids,  181 

—  sulpho-salts,  181 

—  trichloride,  179 

—  trioxide,  180 

—  trisulphide,  181 

—  vermilion,  181    . 
Antimonurreted  hydrogen,  178 
Antimony  1,  180 

—  potassium  tartrate,  430 

—  sulphate,  180 
Antinnonin,  491 
Antipyrine,  551 

—  salicylate,  551 
Antisepsin,  485 
Antitartaric  acid,  428 
Apatite,  162 
Apigenin,  542 
Apiin,  527 

Apiol,  500 
Apoatropine,  55S 
Apomorphine,  556 
Apple  oil,  374 
Applied  chemistry,  2 
Aqua  fortis,  160 

—  regia,  160 
Araban,  444 
Arabic  acid,  460 


678 


INDEX. 


Arabin,  460 
Arabinose,  444 

—  carbonic-acid  lactone,  451 

—  cyanhydrin,  451 
Arabite,  443 
Arabonic  acid,  444 
Arachidic  acid,  377 
Aragonite,  223 
Abutin,  527 
Arecaidine,  553 
Arecaine,  554 
Arecoline,  553 
Argentan,  288 
Argentite,  238 
Argentum,  238 
Arginin,  412 
Argol,  429 
Argon,  182 
Argonin,  562 
Argyrodite,  258- 
Aristol,  503 
Amicin,  529 

Aromatc  compounds,  327 
Arrac,  355 

Arrhenius's  theory,  77 
Arrow  poison,  554 
Arrowroot,  459 
Arsenates,  175 
Arsenical  pyrites,  170 
Arsenic  acids,  175 

—  anhydride,  175 
Arsenic,  170 

—  compounds,  172 

—  detection  of,  177 

—  disulphide,  176 

—  hydrides,  172 

—  mirror,  172 

—  pentasulphide,  176 

—  pent-iodide,  173 

—  pentoxide,  175 

—  sulphide,  176 

—  sulpho-acids,  176 

—  sulpho-salts,  176 

—  tetroxide,  175 

—  tribromide,  173 

—  trichloride,  173 

—  trimethyl,  380 

—  tri-iodide,  173 

—  trioxide,  173 

—  trisulphide,  176 

—  vitreous,  174 
Arsenic,  white,  173 


Arsenic  tests,  Bettendorff's,  177 

Marsh's,  172 

Arsenites,  174 

Arseniurreted  hydrogen,  172 
Arsenious  acid,  174 

—  anhydride,  173 
Arsenolite,  170 
Arsine,  172 
Arsines,  380 
Arsonium  bases,  380 
Artemisin,  529 
Artificial  butter,  435 

—  silk,  458 
Artolin,  565 
Asaprol,  515 
Asarone,  499 
Asbestus,  227 
Ash,  311 
Asparagine,  425 
Aspartic  acid,  424 
Asphalt,  186 
Aspirin,  493 

Asymmetric  carbon  atoms,  39 

—  crystal  system,  35 
Asymmetrical,  469 
Atmid  albumins,  561 

—  proteoses,  561 
Atomic  chains,  298 

—  heat,  23 

—  refraction,  38 

—  rings,  298 

—  volume,  37 

—  theory,  Dalton's,  13 

—  weights,  21 

relation  to  equivalent  weights 

31 

table  of,  25 

Atomicity,  27 
Atoms,  13 

—  spacial  position,  303 
Atoxyl,  485 
Atropanine,  558 
Atropic  acid,  501 
Atropine,  558 
Atroscine,  558 
Augite.  227 
Auramine,  505 
Aurates,  291 

Auric  acid,  291 

—  anhydride,  291 

—  chloride,  291 

—  compounds,  291 


I 


I 


INDEX. 


579 


Auric  hydroxide,  291 

—  oxide,  291 

—  sulphide,  291 
Aurine,  507 
Aurous  chloride,  291 

—  compounds,  290 

—  oxide,  290 
Aurum,  2S9 
Aventurine,  195 
Avidity,  85 
Avogadro's  law,  16 
Axial  symmetry,  308 
Azelaic  acid,  420 
Azides,  151 
Azines,  542 
Azo-black,  510 
Azo-carmine,  543 
Azo-compounds,  465,  509 
Azo-pigments,  510 
Azoimide,  151 

Azole  compounds,  550 
Azolitmin,  493 
Azote,  147 
Azoxazole,  552 
Azoxy  compounds,  509 
Azurite,  233,  237 


/S-compounds,  467,  538 

Bacillol,  491 

Bacteria,  nitrification,  147 

—  niter-forming,  161 

—  niter-splitting,  161 
Balsams,  525 
Barbaloin,  517 
Barbituric  acid,  414 
Barite,  226 
Barium,  226 

—  chloride,  226 

—  chromate,  226 

—  compounds,  226 

—  detection  of,  228 

—  dioxide,  226 

—  ethyl  sulphate,  358 

—  hydroxide,  226 

—  oxide,  226 

—  peroxide,  226 

—  platinum-cyanide,  387 

—  salts,  226 

—  silico-fluoride,  195 

—  sulphate,  226 

—  sulphide.  220 


Barley  sugar,  454 
Baryta  water,  226 
Bases,  84,  99 

—  strength  of,  85 
Basic,  85 

—  anhydrides,  99 
Basicity  of  organic  acids,  335 
Baesorin,  460 

Bauxite,  250 

Bay  oil,  436 

Bayer's  benzene  formula,  462 

Beer,  356 

Beet-root  sugar,  453 

—  molasses,  454 
Behenic  acid,  377 

—  oil,  377 
Bell  metal,  235 
Belladonine,  558 
Belmontin,  342 
Bengalin,  543 
Benzalchloride,  487 
Benzaldehyde,  487 
Benzamide,  489 
Benzazide,  486 
Benzazurin,  510 
Benzene,  478 

—  bromides,  474 

—  chlorides,  474 

—  compounds,  478 

—  derivatives,  327 

—  dicarbonic  acids,  497 

—  disulphonic  acid,  478 

—  formulas,  462 

—  furfuran,  550 

—  halogens,  478 

—  hydrocarbons,  472 

—  nucleus,  465 

—  pentacarbonic  acid,  476 

—  ring,  462 

condensed,  298 

reduced,  463 

secondary,  463 

tertiary,  463 

—  sulphonic  acid,  478 

—  tetracarbonic  acids,  502 

—  theory,  461 
Benzhydrol,  505 
Benzidine,  504 

—  dyes,  510 
Benzil,  488 
Benzihc  acid,  488 
Benzine,  341 


580 


INDEX. 


Benzoates,  489 
Benzodiazines,  543 
Benzodiazole,  551 
Benzofurane,  550 
Benzoic  acid,  488 

benzyl  ester,  489 

sulphimide,  489 

Benzoin,  488,  508 
Benzol,  478 
Benzometadiazine,  543 
Benzonaphthol,  515 
Benzonitrile,  489 
Benzoparadiazine,  543 
Benzophenol,  479 
Benzopurpurin,  510 
Benzopyrazole,  551 
Benzopyridine,  539 
Benzopyron,  541 
Benzopyrrol,  547 

—  compounds,  546 
Benzosol,  480 
Benzothiazole,  552 
Benzothiodiazole,  552 
Benzothiophene,  550 
Benzotrichloride,  487 
Benzoyl,  487 

—  acetic  acid,  477 

—  benzoate,  489 

—  benzoic  acid,  505 

—  chloride,  489 

—  glycocoll,  490 

—  hydrazide,  486 
■ —  morphine,  556 

—  ornithin,  489 

—  per  acid,  489 

—  peroxide,  489 

—  salicin,  528 
Benzyl  acetate,  487 

—  alcohol,  487 

—  amine,  487 

—  benzoate,  489 

—  chloride,  487 

—  cinnamate,  501 

—  compounds,  487 

—  cyanide,  487 

—  mustard-oil,  487 

—  phenol,  505 

—  sulphocyanide,  487 

—  toluene,  505 
Berberine,  555 
Bergamot  oil,  521 
Berthollet's  silver  fulminate,  241 


Beryll,  227 
Beryllium,  227 

—  alloy,  227 
Bessemer  process,  281 

—  steel,  2S1 
Betaine,  369,  398 

Beta  compounds,  467,  538 
Beta-naphthol,  515 
Beta-orcin,  496 
Beta-sterin,  526 
Betite,  482 

Bettendorff's  arsenic  test,  177 
Beverages,  alcoholic,  355 
Biebricher,  scarlet,  510 
Bile  acids,  370 

—  mucin,  566 

—  pigments,  546 
Bilicyanin,  546 
Bihfuscin,  546 
Bilihumin,  546 
Bilineurin,  379 
Biliprasin,  546 
Bilirubin,  546 
Biliverdin,  546 
Biliverdic  acid,  545 
Bioses,  447,  453 
Birotation,  452 
Bismarck-brown,  510 
Bismuth,  263 

—  alloys,  264 

—  compounds,  264 

—  detection  of,  265 

—  gallate,  basic,  295 

—  gallate-iodide,  495 

—  group,  263 

—  hydroxide,  264 

—  nitrate,  264 

—  pentoxide,  264 

—  salicylate,  492 

—  salts,  264 

—  subnitrate,  265 

—  sulphide,  265 

—  tetroxide,  264 

—  trioxide,  264 

—  tribromphenolate,  479 
Bismuthic  acid,  264 

—  anhydride,  264 
Bismuthinite,  263 
Bisque,  253 
Bister,  274 

Bitter-almond  oil,  487,  521 
artificial,  478 


INDEX. 


581 


Bitter-almond  oil,  green,  507 

camphor,  508 

Bitter  earth,  228 

—  principles,  529 

—  water,  117 
Biuret,  413 

—  reaction,  410,  562 
Bixin,  531 

Black  copper,  234 

—  lead,  167 
Bleaching  powder,  221 
Blendes,  119 

Blood  casein,  564 

—  carbon,  187 

—  crystals,  Teichmann's,  545 

—  detection  of,  545,  566 

—  pigments,  545,  566 

—  stone,  277 
Blow-pipe,  93 
Bodies,  1 

—  amorphous,  34 

—  aliphatic,  326 

—  aromatic,  327 

—  crystalline,  33 

—  cyclic,  327 

—  dissolved,  46 

—  explosive,  73 

—  gaseous,  40 

—  liquid,  37 

—  organized,  4 

—  organic,  4 

—  radio-active,  272 

—  simple,  5 

—  solid,  33 

—  super-cooled,  35 

—  super-fused,  35 
Boiler  incrustation,  224 
Boiling,  37 

Boiling-point,  33,  37,  320 
Bolognian  stone.  220 
Bomb,  calorimetric,  68 
Bone-ash,  162 
Bone-oil,  538 

Boracic  acid,  184 
Boracite,  183 
Borates,  185 
Borax,  212 

—  tartar,  430 
Borethyl,  381 
Boric  acids,  184 

—  anhydride,  184 
Borides,  183 


Bormethyl,  381 
Borneo  camphor,  524 
Borocalcite,  183 
Borneo],  524 
Boron,  183 

—  carbide,  184 

—  hydrides,  184 

—  nitride,  184 

—  trichloride,  184 

—  trifluoride,  184 

—  trioxide,  184 
Bottle-glass,  224 
Bournonite,  181 
Boyle's  law,  15 

Brain's  explosive -powder,  458 

Brandy,  355 

Brasilein,  542 

Brasilin,  542 

Brass.  235 

Brassidic  acid,  441 

Brassylic  acid,  420 

Braunite.  273 

Bricks,  253 

Brilliant  black,  510 

—  green,  507 

—  yellow,  510 
Brine  springs,  117 
Britannia-metal,  178 
Broggerite.  182 
Bromine.  139 

—  detection  of,  140 

—  hydrate,  140 

—  solid,  140 

—  oxy  acids.  141 

—  water.  140 

Brom  acetanilide,  485 
Bromethyi.353 
Bromides,  141 
Bromipin,  436 
Bromite.  140 
Brom  benzene,  474 
Bromhaemol,  563 
Bromic  acid,  141 
Bromates,  142 
Bromoform,  348 
Brom-succinic  acid,  42 
Bronzes,  235 
Brookite,  262 
Brown  coal.  188 
tar,  323 

—  hsematite,  277 

—  stone.  273 


582 


INDEX, 


Brucine,  554 
Brunswick-green,  237 
Bryonin,  529 
Bunsen  burner,  93 
Butane,  372 
Butenyl,  431 
Butine,  441 
Butter,  435 

—  of  antimony,  179 

—  of  tin,  257 
Butyl,  372 

—  alcohol,  373 

—  benzenes,  472 

—  compounds,  372 

—  hydride,  372 
Butylene,  394 
Butyric  acids,  373 

—  acid  fermentation,  373 


Cacodyl  compounds,  380 
Cadaver  alkaloids,  398 

—  poisons,  398 
Cadaverin,  398 
Cadmium,  232 

—  amalgam,  243 

—  detection  of,  233 

—  hydroxide,  233 

—  oxide,  233 

—  salts,  233 

—  sulphate,  233 

—  sulphide,  233 

—  yellow,  233 
Caesium,  215 
Caffeic  acid,  501 
Caffeine,  418 

—  salicylate,  418 
Cajeputene,  522 
Cajeput  oil,  521 
Cajeputol,  524 
Calamine,  230 
Calcite,  223 
Calcium,  219 

—  butyrate,  373 

—  carbonate,  223 

—  carbide,  223 

—  citrate,  431 

—  chloride,  221 

—  detection  of,  225 

—  fluoride,  221 

—  hydrate,  220 

—  hydrosulphide,  220 


Calcium  hydroxide,  220 

—  hypochlorite,  221 

—  isobutyrate,  374 

—  lactate,  406 

—  manganite,  275 

—  metaphosphate,  162 

—  naphthol  disulphonate,  515 

—  nitrate,  206 

—  orthoplumbate,  262 

—  oxalate,  423 

—  oxide,  219 

—  permanganate,  277 

—  phosphate,  223 

—  phosphide,  165 

—  polysulphides,  220 

—  sihcate,  224 

—  sulphate,  222 

—  sulphide,  220 

—  sulphite,  125 

—  tartrate,  430 

—  tungstate,  271 
Calcspar,  223 

Calculation  of  organic  analysis,  312 

—  of  volume  weight  of  gases,  43 
Calomel,  243 

Caloric,  68 
Calorimeter,  68 
Calamus-oil,  521 
Campferid,  541 
Camphanes,  519 
Camphene  structure,  519 
Camphanic  acid,  523 
Camphenes,  522 
Camphor,  523 

—  artificial,  522 
Camphoric  acid,  523 
Camphoronic  acid,  523 
Cane  sugar,  453 
Cannabinol,  503 
Cantharic  acid,  503 
Cantharinic  acid,  503 
Cantharidin,  503 
Caoutchouc,  523 
Capaloin,  517 
Capric  acid,  376 
Caproic  acid,  376 
Caprylic  acid,  376 
Capsaicin,  529 
Caramel,  454 
Carawav-oil,  521 
Carat,  290 
Cardinene,  522 


INDEX. 


583 


Carlsbad  salts,  211 
Carmine,  518 
Carmine-red,  518 
Carminic  acid,  518 
Carnallite,  228 
Camelian,  195 
Carnic  acid,  568 
Carnine,  416 
Camotite,  265 
Caro's  reagent,  131 
Carotin,  532 
Carthanim,  531 
Carthartogenic  acid,  527 
Carthartomannite,  483 
Caryophyllene,  522 
Carvacrol,  503 
Carvene,  522 
Carvestrene,  522 
Carvol,  523 
Carvone,  523 
Cascarillin,  529 
Carbamide,  409 
Carbamic  acid,  409 

—  acid-ester,  409 
Carbanilide,  485 
Carbazole,  504 
Carbides,  186 
Carbimide,  392 
Carbinol,  329,  349 
Carbohydrates,  447 
Carboformal,  350 
Carbolic  acid,  476 

crude,  479 

Carbolic-oil,  473 
Carbolic  water,  479 
Carbon,  186 

—  estimation  of,  309,  311 

—  compounds,  296 

with  halogens,  188 

oxygen,  188 

sulphur,  192 

nitrogen,  193 

hydrogen,  188 

Carbon  chains,  298 

heterocyclic,  298 

heterocatenic,  298 

homocyclic,  298 

homocatenic,  298 

normal,  302 

—  atom,  tetrahedra,  303 
asymmetric,  39 

—  group,  185 


Carbon  rings,  298 

Carbon  compounds,  297 

chemistry  of,  304 

classification,  326 

action    of    chemical    agents 

upon,  321 

of  ferments  upon,  324 

of  heat  upon,  323 

elementary  analysis  of,  309- 

311 

halogen  derivatives  of,  478, 

348 

isomers  of,  300,  466 

configuration  of,  303 

constitution  of,  317 

molecular  formulae  of,  313 

nomenclature  of,  328,  471, 

535 

optical  behavior  of,  38,  321 

physical  properties  of,  320 

melting-point     and     boiling- 
point  of,  320 

sterisomerism  of,  302 

structure  of,  317 

substitution  of,  299 

transformations  of,  321 

decompositions  of,  321 

composition  of,  296 

Carbon  dioxide,  190 

detection  of,  191 

—  disulphide,  192 

—  monoxide,  188 

detection  of,  189 

haemoglobin,  189,  566 

—  monosulphide,  192 

—  oxychloride,  190 

—  ox  y  sulphide,  193 

—  tetrachloride,  348 
Carbonic  acid,  191,  408 

— ^  —  amide  derivatives,  409 

detection  of,  191 

esters  of,  408 

—  anhydride,  190 
Carbonates,  191 
Carbonimide,  392 
Carbonization  steel,  281 

—  zone,  280 
Carbonyl,  96 

—  chloride,  190 

—  disulphocarbonic  acid,  408 
Carborundum,  194 
Carbostyril,  540 


584 


INDEX. 


Carboxyl,  329 

—  urea,  413 
Carbylamines,  391 
Casein,  565 
Cassava  starch,  459 
Cassiterite,  255 
Cast  iron,  279 

—  steel,  281 
Castor-oil,  436 
Catechin,  505 
Cation,  75 
Cathartic  acid,  527 
Cathecu  tannic  acid,  496 
Cat's  eye,  195 
Caulosterin,  526 
Caustic  ammonia,  149 

—  lime,  220 

—  potash,  203 

—  soda,  209 
Catalase,  571 
Catalysis,  66 
Cathode,  75 
Cedrene,  522 
Cellulase,  570 
Celloidin,  458 
Celluloid,  458 
Cellulose,  456 

—  nitrates,  457 
Cement,  220 
Cementation  steel,  281 
Central  formula,  462 
Cephseline,  559 
Cerasin,  527 
Cerebrin,  527 
Cerebrose,  452 
Cerebrosides,  527 
Ceresin,  342 
Cerium,  247 

—  oxide,  247 
Cerite,  248 
Cerotene,  394 
Cerotic  acid,  377 
Cerotin,  375 
Cerussite,  259 
Ceryl  alcohol,  375 

—  cerotate,  375 
Cetin,  375 
Cetraric  acid,  497 
Cetyl  alcohol,  375 
■ —  palmitate,  375 
Cevadilline,  559 
Cevadine,  559 


Chain  isomerides,  302 

—  of  carbon,  298 
Chalcc^ite,  233 
Chalcopyrite,  233 
Chalcedony,  195 
Chalybeate  water,  117 
Chalk,  223 
Chamber  acid,  128 
Chance-Claus  process,  213 
Chemistry,  1,  31 

—  general,  3 

—  analytical,  2 

—  applied,  2 

—  inorganic,  95 

—  classification  of,  2 

—  of  the  carbon  compounds,  3,  296 

—  organic,  296,  300 

—  physical,  3 

—  pur«,  2 

—  special,  3 

—  synthetical,  2 

—  systematic,  3 

—  theoretical,  3 
Chemical  affinity,  7,  58 

—  luminosity,  91 
Cheese,  565 

—  oxide,  376 

—  poison,  398 
Chelidonic  acid,  541 
Chenocholic  acid,  370 
Chenotaurocholic  acid,  401 
Cherry  gum,  460 

Chili  saltpeter,  212 
Chitin,  567 
Chitosan.  567 
Chloral,  360 
Chloral  alcoholate,  360 
-^-  chloroform,  347 

—  formamide,  361 

—  hydrate,  361 
Chloranhvdrides,  160 
Chloranii;  482 
Chlorates,  138 
Chloric  acid,  138 

—  anhydride,  138 
Chlorine,  132 

—  bleach,  134 

—  detection  of,  134 

—  dioxide,  137 

—  heptoxide,  139 

—  hydrate,  134 

—  monoxide,  137 


INDEX 


585 


—  pentoxide,  137 

—  tetroxide,  137 

—  trioxide,  137 

—  water,  134 
Chlorous  acid,  137 
Chlorites,  137 
Chlorite,  227 
Chloracetic  acids,  368 
Chlorbenzene,  474 
Chlorcyanogen,  391 
Chlorhydritis,  395,  434 
Chlormei-tiyl-menthyl  ether,  524 
Chlorpicrin,  349 

Chlorides,  136 

—  of  the  fatty  acids,  368 

—  of  hme,  221 

—  of  sulphur,  139 
Chloroaurates,  291 
Chloroplatinates,  293 
Chloroform,  347 
Chlorophan,  532 
Chlorophyll,  545 
Choke  damp,  190 
Cholalic  acid,  370 
Choleic  acid,  370 
Cholesterin,  526 

—  fatty-acid  ester,  526 
Cholesterines,  525 
Cholesterols,  525 
Cholestrophan,  414 
Choletelin,  546 
Cholic  acid,  370 
ChoUne,  379 
Chondrin,  569 
Chondrigen,  569 
Chondroitin,  569 

—  sulphuric  acid,  569 
Chondromucoid,  567 
Chondrosin,  569 
Chrom  alum,  252 
Chrom  carmine,  269 
Chrom  iron  ore,  266 
Chrom  orange,  269 
Chrom  red,  269 
Chrom  yellow,  269 
Chromium,  266 

—  detection  of,  270 

—  alloys.  266 

—  sesqui oxide,  267 

—  trioxide,  268 

—  group,  metals  of,  265 

—  cinnabar,  269 


Chromic  anhydride,  268 

—  compounds,  267 

—  hydroxide,  267 

—  oxide,  267 

—  salts,  267 
Chromic  acid,  268 
Chromates,  268 
Chromites,  267 
Chromite,  266 
Chromogens,  530 
Chromophan,  532 
Chromophore  group,  530 
Chromoproteids,  565 
Chromous  compounds,  267 

—  chloride,  267 

—  hydroxide,  267 

—  oxide,  267 

—  oxychloride,  26S 
Chromyl  chloride,  268 
Chymosin,  571 
Chrysamin-yellow,  510 
Chrysaniline,  540 
Chrysarobin,  517 
Chrysene,  513 
Chrysine,  541 
Chrysoberyll,  227 
Chrysoidin,  510 
Chrysophanic  acid,  517 
Chrysophyll,  532 
Chrysoprase,  195 
Cinchomeronic  acid,  539i 
Cinchonidine,  555 

—  salts,  555 
Cinchonine,  555 
Cinene,  522 
Cineol,  524 
Cinnabar,  245 
Cinnamei'n,  501 
Cinnamic  acid,  500,  521 

benzyl  ester,  501 

cinnamic  ester,  501 

—  aldehyde,  500 

—  ester,  500 
Cinnamol,  498 
Cinnamyl  alcohol,  500 

—  cinnamate,  501 
Cinnoline,  543 
Circular  polarization,  38 
Cis  form,  308 
Citraconic  acid,  431 
Citral,  444 

Citrates,  431 


586 


INDEX, 


Citrene,  522 
Citric  acid,  4S!^ 
Citrine,  195 
Citronellal,  439 
Citronellol,  439 
Classification  of  chemistry,  2 

—  of  the  elements,  95 

—  of  the  carbon  compounds,  326, 

471,  536 

—  of  the  metals,  198 

—  of  the  non-metals,  103 
Clauss's  benzene  formula,  462 
Clay,  252 

Clay  ironstone,  277 

Cleavage,  hydrolytic,  87,  357 

Clevite,  182 

Clinorhombic  system  of  crystals,  35 

Clovene,  522 

Clove-oil,  521 

Cnicin,  527 

Coal,  188 

Coal  benzine,  478 

Coal-tar,  323 

Cobalt,  285 

—  bloom,  285 

—  compounds,  286 

—  detection  of,  287 

—  monoxide,  286 

—  pyrites,  285 

—  sesqui oxide,  286 

—  ultramarin,  254 

—  yellow,  287 
Cobaltamine  salts,  286 
Cobaltic  compounds,  286 
Cobaltic-cobaltous  oxide,  286 
Cobaltic  hydroxide,  286 

—  oxide,  286 

—  salts,  286 
Cobaltous  compounds,  286 

—  aluminate,  254 

—  chloride,  286 

—  hydroxide,  286 

—  nitrate,  286 

—  oxide,  286 

—  silicate,  286 

—  sulphate,  286 

—  sulphide,  286 
Cobaltite,  285 
Cocaine,  558 
Cocao  butter,  436 
Cochineal,  518 
Coconut-oil,  436 


Coefficient  of  refraction,  38 

Coerulein,  508 

Ccerulignone,  504 

Codeine,  556 

Cod-liver  oil,  436 

Coffee  tannic  acids,  496 

Cognac,  355 

Coke,  188 

Colchicine,  559 

Colcothar,  130 

Cold  produced  by  evaporation,  41 

Colestine,  225 

Collagen,  569 

Collidine,  538 

Collocynthein,  527 

Collodium,  458 

—  cotton,  458 
Colloids,  47 
Collomucoid,  567 
Colloxylin,  458 
Colocynthin,  527 
Colombin,  529 
Colophene,  523 
Colophonium,  525 
Colostrum  globulin,  564 
Columbite,  265 
Columbium,  265 
Comanic  acid,  541 
Combining  weights,  12,  32 
Combustion,  91,  109 

—  heat  of,  68 

—  zone,  281 
Comenic  acid,  541 
Common  salt,  210 
Complex  salts,  102 
Compounds,  acyclic,  326 

—  alicyclic,  327 

—  aliphatic,  326 

—  aromatic,  327 

—  azocarbocyclic,  534 

—  binary,  96 

—  carbocyclic,  326 

—  catenic,  326 

—  divalent,  394 

—  endothermic,  68 

—  exothermic,  68 

—  heptavalent,  447 

—  heterocarbocyclic,  326 

—  hexavalent,  445 

—  homocarbocyclic,  326 

—  homologous,  299 

—  hydroaromatic,  463 


INDEX. 


587 


Compounds,  hydrocarbocyclic,  463 

—  inorganic,  3,  95 

—  isocarbocyclic,  326 

—  isomeric,  80,  300,  466 

—  metalio-organic,  381 

—  metameric,  301 

—  mixed,  337 

—  monavalent,  339 

—  normal,  302 

—  organic,  4,  296 

—  pentavalent,  443 

—  primary,  329 

—  polymeric,  300 

—  saturated,  297 

—  secondary,  329 

—  stereoisomeric,  303 

—  trivalent,  431 

—  tenary,  97 

—  tertiary,  97 

—  tetravalent,  441 

—  unknown  constitution,  327 

—  unsaturated,  297 
Concentration  cells,  89 
Conchiolin,  569 
Concretions,  223 
Condensation,  319 

Conditions   for   chemical   transfor- 
mations, 8 
Conductors,  74 
Configuration,  304 
Conglutin,  565 
Congo-red,  510 
Conhydrine,  554 
Coniceine,  554 
Coniferin,  527 
Coniferyl  alcohol,  499 
Coniine,  539,  554 
Conservation  of  energy,  2 

—  of  matter,  10 
Constantan,  288 
Constitution,  29,  296,  328 
Constitutional  formulae,  30,  317,  461 
Constituents    of    chemical    equilib- 
rium, 63 

Constitution,     relationship    of,     to 

physical  properties,  320 
Constant  of  interf  acial  angles,  34 
Contact  action,  66 

—  substances,  66 
Conversion  saltpeter,  207 
Converter,  281 
Convolvulin,  527 


Convolvulinolic  acid,  527 
Copaiba  balsam,  525 
Copelidines,  538 
Copper,  233 

—  alloys,  235 

—  alum,  237 

—  amalgam,  243 

—  ammonia  compounds,  237 

—  carbonate,  237 

—  coins,  235 

—  compounds,  236 

—  detection  of,  237 

—  glance,  233 

—  pyrites,  233 

—  rust,  237 

—  solution,  alkaline,  236 

—  vitriol,  236 
Coprolites,  162 
Coprosterin,  526 
Corals,  223 
Corallines,  508 
Cordials,  355 
Cornein,  569 
Corundum,  249 
Cotarnine,  556 
Cotoin,  482 
Cotton,  456 
Coumalic  acid,  541 
Coumalin,  541 
Coumarin,  501,  541 
Coumaric  acid,  501 

—  anhydride,  501 
Cream  of  tartar,  429 
Creatine,  412 
Creatinine,  412 

—  zinc  chloride,  413 
Creosol,  493 
Creosotal,  493 
Creosote,  493 

—  carbonate,  493 
Cresolin,  491 
Cresols,  491 
Cresotic  acids,  496 
Cresylic  acid,  491 
Crocein-scarlet,  510 
Crocin,  532 
Crocoite,  259 
Crookesite,  255 
Crotin,  572 
Croton-oil,  436 
Crotonic  acids,  440 

—  aldehyde,  360 


588 


INDEX. 


Crotonyl,  432 
Crotonylene,  441 
Crown  glass,  224 
Crude  formose,  350 

—  iron,  279 
Cryohydrates,  50 
Cryolite,  248,  250 
Cryptidine,  539 
Crystal  axes,  34 

—  blue,  507 

—  violet,  507 
Crystals,  34 

—  enantimorphic,  305 
Crystal  forms,  34 

—  glass,  224 
Crystallin,  565 
Crystalline  bodies,  34 
Crystallography,  34 
Crystalloids,  47 
Crystallose,  489 
Crvstal  systems,  34 
Cubebin,'500 
Cumarone,  550 
Cumene,  591 
Cumic  acid,  503 
Cumic  aldehyde,  503 
Cuminil,  488 
Cuminoin,  488 
Cuminol,  503 
Cumol,  501 

Cumvl  alcohol,  503 
Cupellation,  238 
Cupreol,  526 
Cupric  acetate,  364 

—  aceto-arsenite,  364 

—  ammonium  salts,  237 

—  arsenite,  175,  364 

—  carbonate,  237 

—  chloride,  237 

—  compounds,  236 

—  ferrocyanide,  389 

—  hydroxide,  236 

—  oxide,  236 

—  sulphate,  236 

—  sulphide,  236 
Cuprite,  233 
Cuprous  acetylene,  442 

—  compounds,  235 

—  hydroxide,  235 

—  manganese,  273 
Cuprous  oxide,  235 

—  salts,  235 


Cuprous  sulphide,  235 
Cuprum,  233 
Curarine,  554 
Curcumin,  531  . 
Cyanamide,  391 
Cyanates,  392 
Cyanchol,  526 
CyaiieUde,  392 
Cyanimes,  540 
Cyanhydrins,  451 
Cyanhydroxide,  392 
Cyanic  acid,  392 
Cyanides,  485 
Cyanidine,  543 
Cyanpropionic  acid,  422 
Cyanogen,  383 

—  chloride,  391 

—  compounds,  382 
Cyanuramide,  392 
Cyanuric  acid,  392 

—  chloride,  391 
Cyclanes,  338 

Cyclic  compounds,  327 
Cyclo-compounds,  338 
Cyclo-heptane,  557 
Cvclo-olefines,  464 
Cymol,  503 

—  phenols,  503 
Cystein,  407 
Cystin,  407 

d-compounds,  448 
J,  470 

Dahlia-violet,  507 
Dalton's  atomic  theory,  13 
Dammar  gum,  525 
Daniell's  cell,  90 
Daphnetin,  501 
Daphnin,  501 
Datiscetin,  541 
Daturin,  55S 
Deacon's  process,  133 
Decane,  340 
Decay,  109,  325 
Dechenite,  265 
Decipium,  247 
Decomposition     of 

pounds,  321 
Decvl  alcohol,  342 
Delft  ware,  2^53 
Dermatol,  495 
Desinfectol,  491 


organic    com< 


INDEX. 


589 


Desmotropism,  300 
Detonating  gas,  112 
Deuteroproteoses,  568 
Dextrins,  459 
Dextrolactic  acid,  407 
Dextrotartaric  acid,  428 
Dextrose,  451 
Dextrosecyanhydrin,  451 
Diabetic  sugar,  451 
Diabetin,  452 
Diacetonamine,  372 
Diacetylene,  447 
Diacetyl  tannin,  495 
Diacid  anhydrides,  404 
Diagonal  formula,  463 
Dialdehyde,  402 
Dialuric  acid,  414 
Dialysator,  47 
Dialysis,  47 
Diamide,  151 
Diamidobenzene,  483 
Diamidocaproic  acid,  376 
Diamidodiphenyl,  504 
Diamidophenol,  480 
Diamidovaleric  acid,  375 
Diamines,  330,  397 
Diamine  dyes,  510 
Diammonium  salts,  151 
Diamond,  186 
—  bort,  187 
Diamylene,  394 
Dianthin,  508 
Diaspore,  250 
Diastases,  570 
Diazin  compounds,  542 
Diazo-compounds,  465,  511 
Diazoamidobenzene,  511 
Diazobenzene  salts,  511 
Diazole  compounds,  550 
Diazonium  compounds,  511 
Dibenzodiazines,  543 
Dibenzopyrone,  542 
Dibenzyl,  508 
Dibromsuccinic  acid,  424 
Dichloracetic  acid,  368 
Dichloracetone,  430 
Dichloracetonic  acid,  430 
Dichlorhydrins,  434 
Dichromic  acid,  269 
Dicinnamic  acid,  502 
Dicyanogen,  383 
Dicyandiamide,  392 


Diethylamine,  378 
Diethylendiamine,  398,  543 
Diethyline,  434 
Diethyloxylethenyldiphenylami- 

dine,  486 
Diethylglycolate,  403 
Diffusion,  46 

—  method,  454 
Digallic  acid,  495 
Digitalis  glucosides,  527 
Digly collie  acid,  405 
Dihydrazons,  450 
Dihydrobenzene,  463 
Dihydropyrazole,  550 
Dihydropyrrol,  545 
Diketones,  488 

Dimercuric-ammonium  iodide,  246 
Dimethylacetylene,  447 
Dimethylaniline,  484 
Dimethylarsin  compounds,  380 
Dimethylbenzenes,  496 
Dimethvldiarsine  compounds,  380 

—  oxide,  380 

Dimethylethyl  carbinol,  375 
Dimethyl  ketone,  371 
Dimethyl  parabanic  acid,  414 
Dimethyl  pyridine,  538 
Dimethyl  pyrrol,  545 
Dimethyl  quinoline,  539 
Dimethyl    trioxy    cinnamic     acid, 

501 
Dimethyl  urea,  413 
Dimethyl  uric  acid,  416 
Dimethyl  xanthine,  416 
Dimorphism,  35 
Dinitro  naphthalene,  514 

—  naphthol,  515 

—  ortho  cresol  potassium,  491 
Dionin,  556 

Diorsellic  acid-erythrite  ester,  496 
Dioxindol,  547 
Dioxyacetone,  433 
Dioxyanthraquinone,  516 
Dioxybenzenes,  480 
Dioxybenzoic  acids,  494 
Dioxycinnamic  acids,  501 
Dioxycoumarins,  501 
Dioxydiphenyl,  504 
Dioxymalonic  acid,  434 
Dioxyphenvlacetic  acid,  498 
Dioxyphthalic  acids,  477,  497 
Dioxy propionic  acid,  433 


590 


INDEX. 


Dioxypurin,  416 
Dioxysuccinic  acid,  427 
Dioxy tartaric  acid,  428 
Dioxy toluenes,  493 
Dioxy toluic  acid,  476,  498 
Dioxy  xylenes,  498 
Dipara  amidodiphenyl,  510 
Dipentene,  522 
Diphenic  acid,  518 
Diphenyl,  504 
Diphenyl  acetylene,  509 

—  amine,  4S3,  485 

—  blue,  507 

—  carbinol,  505 

—  carbonic  acid,  504 

—  compounds,  504 

—  dicarbonic  acid,  504 

—  dike  tone,  488 

—  ethane,  505,  508 

—  ethylene,  505,  508 

—  ketone,  505,  508 

—  methane,  505 

—  tetramethylendicarbonic     acids, 

501 

—  urea  485 
Diphenylen  diketone,  516 

—  imide,  504 

—  ketone  oxide,  541 

—  methane,  505 

—  oxide,  504 

—  sulphide,  504 
Depilatory,  Bottger's,  220 
Dippel's  animal  oil,  538 
Dipropargyl,  447 
Dipyndyl,  538 
Disaccharides,  453 
Disacryl,  439 
Disazo-compounds,  510 
Discharge,  dark,  110 
Disilicic  acid,  197 
Disilicates,  197 
Disodium  glycol,  401 
Dissociation,  70 

—  thermic,  71 

—  electrolytic,  77,  79 

—  hydrolytic,  86 

—  degree,  78 

—  heat,  68 

—  tension,  71 

Disubstitution  products,  467 
Disulphides,  351 
Disulpho-carbonic  acid,  193,  408 


Disulpho-ethyl  dimethyl  methane, 
372 

Disulpho-dimethyl  methane,  372 

Disulpho-methyl-ethylmethane,  372 

Disulphuric  acid,  130 

Distillation,  50,  323 

Diterpenes,  522 

Dithio-diamido-ethylidene  lactic 
acid,  407 

Dithiodiphenyl,  504 

Dithionic  acid,  124 

Dithiosalicylic  acid,  493 

Dithymol  di-iodide,  503 

Ditolyl,  504 

DiureTds,  413 

Diuretin,  418 

Dobreiner's  lamp,  105 

Dodecane,  340 

Dodecyl  alcohol,  342 

Dolomite,  223 

Double  salts,  102 

Double  tetrahedra  of  the  C  atouui 
305 

Dowson's  gas,  188 

Drummond  lime-light,  113 

Dualin,  458 

Duatal,  480 

Duboisine,  558 

Dulcin,  480 

Dulong-Petit's  law,  22 

Dumas  method  for  estimating  ni- 
trogen, 312 

Durene,  502 

Durenols,  474 

Dutch  white  lead,  261 

Dynamogen,  562 

Dynamics,  chemical,  59 

Dynamite,  434 

Dyslysins,  370 

Dysprosium,  247 

Dysproteoses,  568 

Earth-nut  oil,  377 
Earthenware,  253 
Earthy  metals,  247 
Ebonite,  523 
Ecgonine,  557 
Ecrasite,  479 
Edinol,  491 

Effervescent  magnesia,  431 
—  powder,  430 
Efflorescence,  115 


INDEX. 


591 


Egg-shell,  223 
Eigone,  562 
Eikonogen,  515 
Elseoptenes,  521 
Elaic  acid,  440 
Elaidic  acid,  440 
Elastin,  569 
Electroaffinity,  82 
Electrochemistry,  74 
Electrodes,  75 
Electrolysis,  74 
Electrolytes,  74,  78 

—  power  of  reaction  of,  83 
Elements,  5,  25,  54,  55 

—  arrangement  according  to  their 

atomic  weights,  54,  55 

—  equivalent  weights  of,  12,  31 

—  galvanic,  88 

—  classification  of,  95,  96 

—  periodic  system  of,  54,  55 

—  symbols  of,  25 

—  table  of,  25 

—  unknown,  5 

—  valence  or  atomicity  of,  27 

—  of  the  earth's  crust,  6 
Elementary  analysis,  309,  311 
Elemi  resin,  525 
Ellagic-tannic  acid,  496 
Emerald,  227 

Emetine,  559 
Emission  spectrum,  44 
Emodin,  517 
Emulsin,  571 
Emulsions,  437 
Enantiomorphism,  305 
Encephalin,  527 
Endo  substitution,  467 
Endothermic  reactions,  68 
Energy  and  affinity,  7 
Energy,  58 

—  available,  59 

—  chemical,  5S,  67,  74,  91 

—  electrical,  74 

—  mechanical,  58 

—  thermic,  67 

—  radiant,  91 

—  varieties  of,  58 
Enol  structure,  338 
Enzymes,  570 
Eosine,  508 
Epichlorhydrin,  434 
Epsom  salts,  229 


Equations,  chemical,  24 
Equilibrium,  chemical,  60,  62 

—  condensed,  63 

—  heterogeneous,  63 

—  homogeneous,  63 

—  non-homogeneous,  63 

—  variable,  62 
Equimolecular,  19 
Equisetic  acid,  431 
Equivalence  of  the  elements,  31 
Equivalent  weights,  12,  31 
Erbium,  247 

Ergotinin,  559 
Erica,  552 
Ericolin,  527 
Ericonol,  527 
Erucic  acid,  441 
Erythrin,  496 
Erythrin  nitrate,  443 
Erythrite,  285 
Erythrite,  443 

—  nitrate,  443 
Erythritic  acid,  443 
Erythrocentaurin,  529 
Erythrodextrin,  459 
Erythrose,  443 
Erythrosin,  508 
Eseridin,  559 
Eserin,  559 

Esters,  332,  357,  345 
Ester  acids,  332,  358 

—  anhydrides,  404 
Ethane,  353 
Ethenyl,  431 

—  benzene,  498 

—  phenylenamidine,  468 
Ethine,  441 

Ethoxyl,  329 
Ethoxylacetanilide,  485 
Ethoxyaniline,  485 
Ether,  358 

—  petroleum,  341 

—  sulphuric,  358 
Ethers,  332,  359 

—  acids,  332 

—  compound,  332 

—  in  general,  359 

—  mixed,  332,  359 

—  of  phenols,  477 

—  simple,  332,  359 
Ethyl,  328 

—  acetate,  364 


592 


INDEX, 


Ethyl  alcohol,  353 

—  aldehyde,  359 

—  benzene  compounds,  498 

—  bromide,  353 

—  caprilate,  376 

—  caprinate,  376 

—  chloride,  353 

—  ether,  358. 

—  glycolate,  403 

—  gly collie  acid,  403 

—  hydride,  353 

—  hydroxide,  353 

—  morphine,  556 

—  nitrate,  356 

—  nitrite,  356 
-T-  oxide,  358 

—  oxyphenylguanidine,  486 

—  peroxide,  359 

—  pyrrol,  545 

—  sulphuric  acid,  357 

—  sulphurous  acid,  401 

—  sulphate,  357 

—  sulphinic  acid,  401 

—  sulphonic  acid,  401 

—  urethan,  409 

—  xanthogenic  acid,  408 
Ethylamine,  378 
Ethylene,  396 

—  alcohol,  399 

—  acids,  405 

—  bromide,  397 

—  chlorhydrin,  400 

—  chloride,  397 

—  compounds,  395 

—  cyanide,  422 

—  diamine,  397 

—  diethyl  ether,  401 

—  dicarbonic  acid,  423 

—  ethenyldiamine,  398,  551 

—  ether,  402 

—  ethyl  ether,  401 

—  glycol,  399 

—  hydrin  sulphonic  acid,  400 

—  lactic  acid,  407 

—  oxide,  402 
Ethylidene  acids,  405 

—  chloride,  397 

—  compounds,  395 

—  cyanide,  422 

—  diethyl  ether,  401 

—  dicarbonic  acid,  425 

—  lactic  acid,  406 


Ethylidene  oxide,  359,  402 
Ethyline,  434 
Eubiol,  562 
Eucain,  539 
Eucalyptol,  524 
Eucasein,  562 
Eudiometer,  154 
Eugenol,  499 
Eulytite,  263 
Euphorbium,  525 
Euphorbon,  529 
Euphthalmin,  539 
Eupitton,  508 
Euquinhie,  555 
Eurhodines,  543 
Eurhodoles,  543 
Europhene,  491 
Eutectic  point,  50 
Euxanthic  acid,  446,  541 
Euxanthon,  541 
Euxenite,  182,  248 
Evaporation,  36 
Evemic  acid,  497 
Exalgin,  485 
Exo  substitution,  467 
Exothermic  reactions,  68 
Explosion,  74 
Explosive  gelatine,  458 

—  oil,  Nobel's,  434 

—  powder,  458 

Extraction  method  for  silver,  238 

Fahl  ores,  181 

Faraday's  law,  75 

Fats,  435 

Fatty  acids,  344 

halogen  substitution,  368 

—  bodies,  326 
Fayence  ware,  253 
Feather  alum,  251 
Fehling's  solution,  236 
Feldspar,  248 
FeUcic  acid,  482 
Fellic  acid,  370 
Fenchen,  522 
Fenchone,  524 
Fennel-oil,  521 
Fergusonite,  182,  248 
Ferments,  324,  570 

—  inorganic,  54 
Ferrates,  284  . 
Ferratin,  562 


INDEX. 


593 


Ferratogen,  562 
Ferric  acid,  284 

—  ammonium  citrate,  431 
sulphate,  284 

—  arsenite,  174 

—  benzoate,  489 

—  carbonate,  284 

—  cinnamate,  500 

—  citrate,  431 

—  chloride,  284 

—  compounds,  283 

—  ferrocyanide,  388 

—  hippurate,  490 

—  hydroxide,  283 

—  oxide,  277,  283 

—  oxy hydroxide,  277 

—  malate,  427 

—  phosphate,  277 

—  potassium  cyanide,  389 

—  silicate,  277 

—  sulphide,  284 

—  sulphate,  284 

—  thiocyanate,  393 
Ferrous-ammoniimi  sulphate,  283 

—  chloride,  281      - 

—  compounds,  282 

—  ferric  cyanide,  389 

oxide,  277 

sulphide,  277 

—  ferrocyanide,  289 

—  hydroxide,  281 

—  iodide,  281 

—  lactate,  406 

—  malate,  427 

—  manganese,  273 

—  oxide,  281 

—  phosphate,  283 

—  potassium  cyanide,  387 

—  siHcate,  277 

—  sulphate,  281 

—  sulphide,  281 
Ferrum  277 
Fersan,  562 
Fermentation,  325,  356 

—  amyl  alcohol,  374 

—  butyric  acid,  373 

—  lactic  acid,  406 
FeruUc  acid,  501 
Fibrin  ferment,  571 

—  globulin,  564 
Fibrins,  567 
Fibrinogen,  564 


Fibroin,  569 

Fichtelite,  518 

Filix  tannic  acid,  496 

Fire-damp,  346 

Fisetin,  541 

Fittig-Wurtz  synthesis,  340 

Fixing  salt,  212 

—  of  photographs,  241 
Flame  coloration,  93 
Flames,  92 
Flavaniline,  540 
Flavone,  541 
Flavopurpurin,  517 
Flint,  195 

—  glass,  224 
Flowers  of  sulphur,  120 
Fluoranthrene,  513 
Fluorene,  505,  518 
Fluorescein,  508 
Fluorides,  145 
Fluorine,  144 
Fluorspar,  144 

Flux,  280 

Force  of  dissociation,  79 
Forge  scales,  278 
Formaldehyde,  349 
FormaUn,  350 
FormalitJi,  350 
Forman,  524 
Formamide,  353 
Formanilide,  485 
Formates,  353 
Formic  acid,  352 
Formin,  398 
Formol,  350 
Formolalbumin,  562 
Formonetin,  528 ' 
Formonitrile,  353 
Formose,  450 
Formiilse.  chemical,  24 

—  empirical,  26 

—  rational,  26 
Fowler's  solution,  207 
Frangulin,  528 
Frankolin,  442 
Freedoms,  64 

—  degree,  64 
Freezing  mixtures,  52 
Freezing-point,  35 

depression,  20,  315 

Friedel-Craft  synthesis,  498 
Fructose,  452 


594 


INDEX, 


Fruit  jellies,  460 
Fruit  sugar,  452 
Fucose,  444 
Fumaric  acid,  427 
FuFane  compounds,  549 
Furanalcohol,  549 
Furazane,  552 
Furfurol,  549 
Furodiazole,  552 
Furoin,  549 
Furol,  549 
Furomonazole,  552 
Fuchsin,  507 
Fusel-oil,  354 
Fusion,  heat  of,  36,  114 
Fusing-zone   of   the   blast-furnace, 
280 

r=  physical  isomerism, 
y-compounds,  538 
Gadinm,  398 
Gadolinite,  248 
Gadolinium,  247 
Galactogen,  562 
Galactonic  acid,  446 
Galactose,  446,  452 
Galactoside,  526 
Galbanum,  525 
Gahnite,  251 
Galangin,  541 
Galena,  259 
Gallanol,  485 
Gallein,  508 
Gallic  acid,  494 

—  alcohol,  494 

—  anilide,  485 
Gallium,  254 

—  alum,  252 

—  sulphide,  254 
Gallocyanin,  544 
Gallogen,  495 
Galvanoplastic,  76 
Garnet,  248 
Garnierite,  287 
Gas  carbon,  187 

—  constants,  43 

—  lime,  220 

—  oil-forming,  396 

—  purification  of,  388 

—  spontaneous  lighter,  105 

—  and  vapor,  40 
Gases,  40 


Gases,  behavior  towards  pressure, 
15,40 

—  calculation  of  weight,  43 

—  combining  proportions  of,  11 

—  density  of,  43,  72,  314,  315 

—  expansion  of ,  15 

—  expansive  force  of,  40 

—  liquefaction  of,  41 

—  mixed,  49 

—  solutions  of,  49 

—  specific  gravity  of,  43 

—  tension  of,  40 

—  volume  of,  43 

—  volume,  relationship  of,  42 
Gaseous  volimie,  calculation  of,  42 
Gasoline,  341 

Gattermann's  method,  488 
Gaultheria  oil,  521 
Gay-Lussac-Dalton  law,  15 
Gay-Lussac's  law  of  volumes,  12 
Gaj-Lussac  tower,  128. 
Geinic  acid,  326 
Gelatine,  569   , 

—  peptones,  569 
Gelatme-forming  substances,  569 
Gelatinoids,  47 

Geles,  54 

Generator  gas,  188 
Gentian  blue,  507 

—  violet,  507 
Gentianose,  456 
Gentiogenin,  528 
Gentiopicrin,  528 
Gentisin,  541 
Gentisic  acid,  494 
Genistein,  505 
Geosote,  481 
Geranial,  444 
Geranic  acid,  445 
Geraniol  444 
German  silver,  288 
Germanium,  258 

—  sulphide,  258 
Germanic  acid,  258 
Gersdorffite,  170.  287 
Gibb's  phase  rule,  64 
Gm,  355 

Glacial  acetic  acid,  362 
Glance,  119 
Glass,  224 
Glauber  salt,  211 
Glaze,  253 


INDEX. 


695 


Gliadin,  567 
Globulins,  564 
Glonoinum,  434 
Glover  tower,  129 
Gluco.     See  also  Glyco. 
Glucase,  570 
Glucinum,  227 
Glucoheptite,  447 
Glucoheptonic  acid,  447 
Glucoheptose,  447 
Gluconic  acid,  446 
Glucononic  acid,  447 
Glucononose,  447 
Glucononite,  447 
Gluco-octite,  447 
^  Gluco-octonic  acid,  447 

Gluco-octose,  447 
Glucoproteids,  566 
Glucosaamines,  450 
Glucosazone,  450 
Glucose,  451 
Glucoses,  451 
Glucosides,  526 
Glucosone,  450 
Glucotannoids,  496,  528 
Glucuronic  acid,  446 
Glue,  569 

—  sugar,  369 
Glutamic  acid,  425 

amide,  426 

Glutamine,  426 
Glutaric  acid,  425 
Gluten,  567 

—  casein,  567 

—  ferment,  571 

—  fibrin,  567 
Glutin,  569 
Glutol,  350 
Glutolin,  569 
Glyceric  acid,  433 

—  aldehyde,  433 
Glycerides,  433 
Glycerine,  432 

—  acetate,  432 

—  anhydride,  434 

—  ester,  434 

—  ethers,  434 

—  monoformate,  438 

—  nitrates,  434 
Glycero-phosphoric  acid,  434 
Glycerose,  433 

Glyceryl,  431 


Glyceryl  oleate,  435 

—  palmitate,  435 

—  stearate,  435 
Glycin,  369,  498 
Glyco.     See  also  Gluco. 
Glyco  alkaloids,  559 
Glycocholic  acid,  370 
GlycocoUs,  336,  369 
GlycocoU  phenetidine,  486 
Glycogen,  459 

Gly collie  acid,  368,  405 
Glycoluric  acid,  414 
Glycols,  399 
Glycol  acetate,  399 

—  aldehyde,  402 

—  anhydride,  399 

—  diethyl  ether,  399 

—  ethyl  ether,  399 

—  methyl  guanidine,  412 

—  sulphuric  acid,  400 
Glycolyl,  404,  414 

—  urea,  414 

—  methyl  guanidine,  412 
Glycoproteids,  566 
Glycose,  451 
Glycuronic  acid,  446 
Glycyrrhetin,  528 
Glycyrrhizic  acid,  528 
Glyoxal,  402 
Glyoxalic  acid,  402 
Glyoxaline,  550 
Glyoxyl  urea,  413 
Glyoxylic  acid,  402 
Gmelin's  reaction,  546 
Gneiss,  248 

Gold,  289- 

—  alloys,  290 

—  coins,  290 

—  colloidal,  290 

—  compounds,  290 

—  chloride,  291 

—  detection  of,  291 

—  group,  288 

—  oxide  ammonia,  291 

—  potassium  cyanide,  290 

—  purple,  292 

—  salt,  291 

—  topaz,  195 

—  washing,  289 
Goidschmidt's    reduction    method, 

249 
Gossypetin,  542 


596 


INDEX. 


Gossypose,  456 
Graduation  house,  210 
Gram,  114 

—  atom,  36 

—  molecule,  36 
.—  volume,  37,  42 
Granite,  248 
Granulose,  458 
Grape  sugar,  451 
Graphite,  187 
Graphitic  acid,  187 
Grass  bleaching,  117 
Greenockite,  232 
Green  soap,  437 
Greiss's  reaction,  511 
Ground  water,  116 
Groups,  96 

Guaiac  resin,  525 
Guaiacol,  480 

—  ester,  480 
•—  salol,  481 

Guanidine,  411 

—  amidovaleric  acid,  412 

—  carbonate,  412 

—  nitrate,  412 
Guanine,  416,  417 
Guano,  162,  417 
Guaranine,  418 
Guavacine,  553 
Guignet's  green,  267 
Gum,  460 

—  animal,  460 

—  benzoin,  525 

—  lac,  525 

—  mucilage,  460 

—  resin,  525 

—  sugar,  444 
Gun  cotton,  457 

—  metal,  235 

—  powder,  207 

smokeless,  457 

Guttapercha,  523 
Gypsum,  222 

Hsemalbumin,  562 
Hsematein,  542 
Hffimatm,  545,  562 

—  hydrochloride,  545 
Hsematochromogen,  545 
Hamotogen,  562 
Hsematoporphyrin,  545 
Haematoxylin,  542 


Haemin,  545 
Hsemochromogen,  545 
Ha?mogallol,  563 
Haemoglobin,  566 
Hsemol,  563 
Hremopyrrol,  545 
Halogens,  132  ^ 

—  estimation  of,   in   organic  com- 

pounds, 310,  312 

—  action  upon  carbon  compounds, 

348,478 
Halogens,    action    upon    the   alky- 

lenes,  397 

upon  the  phenols,  475 

Halogen  derivatives  of  benzene,  478 

of  the  aliphatic  series,  348 

of  the  fatty  acids,  368 

Halogenide  acids,  367 
Haloids,  132 
Haloid  acids,  132 
Hamburg  white,  226 

—  vellow,  269 
Hard  coal,  188 

—  glass,  224 

—  resins,  525 
Hardness  of  water,  116 
Hargreave's  process,  211 
Harmonica,  chemical,  105 
Hatchett's  brown,  489 
Hausmannite,  273 

Heat,    action    upon    organic    com- 
pounds, 323 

—  development.  68 

—  energy  of  the  electric  current,  82 

—  of  decomposition,  68 

—  of  dilution,  68 

—  of  formation,  68 

—  of  hydration,  68 

—  of  reaction,  68 

—  specific,  22 

—  toning,  68 

—  unit,  68 

Heating-zone  of  the  blast-furnace, 

280 
Heavv  metals,  199 

—  oii;  473 

—  spar,  226 
Helenin,  515 
Helianthin,  510 
Helicin,  528 
Helicoproteid,  565 
Heliotrope,  195 


INDEX. 


597 


Heliotropin,  494 
Helium,  182 
Helleborein,  528 
Helvetia  green,  507 
Henry-Dalton's  law,  49 
Hemellithene,  499 
Hemellitic  acid,  499 
Hemialbumoses,  568 
Hemillitic  acid,  499 
Hemipinic  acid,  497 
Hemp-seed  oil,  435 
Heptane,  340 
Heptoses,  448,  451 
Heptyl  alcohol,  375 
Heratol,  442 
Heroin,  556 
Hesperidene,  522 
Hesperidin,  528 
Hesperitic  acid,  501 
Heterocarbocyclic  compounds,  326 
Heteroproteoses,  568 
Heteroxanthine,  416 
Hexachlorbenzene,  474 
Hexachlorethane,  397 
Hexadecane,  340 
Hexagon  scheme,  462 
Hexagonal  crystal  system,  35 
Hexahydrobenzene,  463 
Hexahydrohexaoxybenzene,  483 
Hexahydropyridine,  539 
Hexamethoxylaurine,  507 
Hexamethyl  benzene,  503 
Hexamethylene,  464 
Hexamethylentetramine,  398 
Hexane,  340 
Hexaoxybenzene,  474 

—  potassium,  483 
Hexaoxydiphenyl,  504 
Hexon  bases,  561 
Hexoses,  448,  451 
Hexoxylene,  441 
Hexyl  alcohol,  375 

—  butyrate,  375 
Hexylene,  394 
Hexylic  acid,  376 
Hippurates,  490 
Hippuric  acid,  490 
Histon,  564 
Hoffmann's  anodyne,  359 

—  carbylamine  test,  391 

—  method   for  determining   vapor 

densities,  314 


Hoffmann^s  reaction,  378 

—  violet,  507 
Holmium,  247 
Holocain,  486 
Homatropine,  557 
Homocyclic  compoimds,  326 
Homogentisic  acid,  498 
Homologous  series,  299 
Homopyrocatechin,  493 
Homopyrrol,  545 

Hops  of  beer,  356 
Hop  bitter,  529 
Hornblende,  227 
Horn  silver,  132 
Hiibl's  iodine  equivalent,  440 
Humin,  326 
Humic  acid,  326 
Humus,  326 
Hyalines,  567 
Hvalongens,  567 
Hyacinth,  263 
Hydantoin,  414 
Hydantoic  acid,  414 
Hydracrylic  acid,  407 
Hydrargyrum,  242 
Hydrascin,  555 
Hydrastinine,  555 
Hydrates,  99 
Hydrazides,  337,  357 
Hydrazin,  151,  331 

—  compounds,  151 
Hydrazo  compounds,  509 
Hydrazones,  331,  351,  450 
Hydrazoates,  151 
Hydrazoic  acid,  151 
Hydric,  98,  99 
Hydrides,  105 
Hydrindene,  518 
Hydriodic  acid,  143 
Hydrobenzoin,  508 
Hydrobihrubin,  546 
Hydrobromic  acid,  140 
Hydrocarbons,  328 

—  alicychc,  327 

—  aliphatic,  326 

—  amido  derivatives  of,  330,377,483 

—  aromatic,  327 

—  cyclic,  327 

—  halogen  derivatives  of,  348,  478 

—  in  general,  340 

—  isomerism,  300,  466 

—  normal,  302 


598 


INDEX. 


Hydrocarbons,  primary,  329 

—  saturated,  340 

—  secondary,  329 

—  tertiary,  329 

—  unsaturated,  297 
Hydrocarotin,  529 
Hydrocellulose,  457 
Hydrochlorauric  acid,  291 
Hydrochloric  acid,  135 
Hydrochlorpalladic  acid,  294 
Hydrochlorpalladous  acid,  294 
Hydrochlorplatinic  acid,  293 
Hydrochlorplatinous  acid,  293 
Hydrochromcyanic  acid,  387 
Hydrocinnamic  acid,  502 
Hydrocinnamoin,  509 
Hydrocobaltic  cyanic  acid,  387 
Hydrocoumaric  acid,  502 
Hydrocyanic  acid,  383 
Hydroeyclic  compounds,  463 
Hydroferrocyanic  acid,  387 
Hydroferricyanic  acid,  389 
Hydrofluoric  acid,  144 
Hydrofluosiliric  acid,  195 
Hydrogeles.  54 

Hydrogen,  103 

—  bromide,  140 

—  chloride,  135 

—  compounds  of,  with  metals,  200 

—  estimation     in     organic     com- 

pounds, 311 

—  fluoride,  144 

—  intraradical,  345 

—  sulphide,  122 
Hydrolysis,  87,  357 
Hydromellitic  acid,  503 
Hydroplatinocyanic  acid,  387 
^ydrophlorone,  493 
Hydroquinoline,  539 
Hydroquinone  carbonic  acid,  494 
Hydroquinono,  481 
Hydrosulphides,  93 
Hydrosulphurous  acid,  130 
Hydrosulphuryl,  93 
Hydroxamic  acids,  331 
Hydroximic  acids,  331,  357 
Hydroxyl,  96 

Hydroxy  lamine,  150 

—  salts,  151 
Hygrine,  553 
Hyocholic  acid,  370 
Hyoglycocholic  acid,  370 


Hygroscopy,  116 
Hyoscine,  558 
Hyoscyamine,  558 
Hyper,  99 
Hypo,  99 

Hypobromites,  142 
Hypobromous  acid,  141 
Hypochloric  acid,  137 
Hypochlorites,  137 
Hypochlorous  acid,  137 
Hypogseic  acid,  440 
Hyponitrites,  155 
Hyponitrous  acid,  155 
Hyponitric  acid,  158 
Hypoiodous  acid,  143 
Hypophosphorous  acid,  167 
Hypophosphites,  166 
Hyposulphurous  acid,  130 
Hypotheses,  atomic,  13 

—  of  Le  Bel  and  van't  HofT,  304 
Hypoxanthine,  415 

Hyrgol,  242 

i= inactive,  448 
Ice,  113 

—  manufacture,  149 
Ichthalbin,  562 
Jchthoform,  350 
Ichthulin,  565 
Ichthyol,  324 

—  sulphonic  acid,  324 
Ignition  mass,  249 

—  temperature,  73,  110 
lUuminating-gas,  323 
Imidazole,  550 

Imide  group,  96 

—  bases,  330 
Imides,  420 
Imido,  96 

—  acids,  335 
Imidoalloxanthine,  415 
Imidoether,  335 
Imidothioacids,  335 
Imidothioether,  335 
Imidourea  411 
Imines,  330 
Immedial  black,  552 
Inactivity,  optical,  306,  448 
Indamine,  486 
Indazine,  543 

Indazole,  551 
Indene,  518 


INDEX. 


599 


Index  of  refraction,  38 
India  ink,  187 
Indian  yellow,  541 
Indican,  547 
Indicators,  87 
Indigo  blue,  548 

—  carmine,  549 

—  colors,  549 

—  purpurin,  549 

—  red,  493 

—  sulphonic  acids,  549 
— -  white,  549 
Indigotin,  548 
Indirubin,  549 
Indium,  254 

—  alum,  252 

—  sulphide,  254 
Indoaniline,  486 
Indoin  blue,  543 
Indol,  547 

—  compounds,  546 
Indophenin,  550 
Indophenols,  485 

—  reaction,  485 
Indoxyl,  547 
Indoxylic  acid,  547 

—  sulphuric  acid,  547 
Induction,  photochemical,  94 
Indulines,  543 

Infusorial  earth,  195 
Ingluvin,  570 
Ink,  285,  496 

—  symjDathetic,  286 
Inorganic  chemistry,  3  95 
Inosite,  483 

Inulase,  570 
Inulin,  459 
Intraradical,  345 
Invertase,  570 
Invertin,  570 
Invert-sugar,  454 
lodates,  143 
lodeosin,  508 
Iodic  acid,  143 
Iodides,  143 
Iodide  starch,  459 

—  of  nitrogen,  152 
Iodine,  142 

—  chloride,  142 

—  detection  of,  143 

—  estimation,  312 

—  equivalent,  440 


Iodine  pentoxide,  143 

—  trichloride,  142 
lodipin,  436 
Iodoform,  347 
lodoha'mol,  563 
lodophosphonium,  165 
lodothyrin,  565 

lodoxyquinolin  sulphonic  acid,  540 
Ionization  pressure,  88 

Ions,  75,  77 

—  complexes,  84 

—  electric  quantity,  82 

—  electronegative,  77 

—  elecTtropositive,  77 

—  names  of,  82 

—  velocity  of,  82 
Iridin,  528 
Iridium,  294 
Irigenin,  528 
Iron,  277 

—  ammonium  citrate,  431 

—  ammonium  sulphate,  283 

—  alloys,  278 

—  alum,  252,  284 

—  arsenite,  174 

—  bisulphide,  277 

—  carbide,  278 

—  carbonate,  283 

—  carbonyl,  189 

—  detection  of,  285 

—  group,  metals  of,  272 

—  manganese  peptone,  568 

—  meteoric,  277 

—  nitride,  277 

—  ores,  277 

—  oxide  solution,  dialysis  of,  284 

—  oxychloride,  284 

—  passive,  278 

—  peptone,  568 

—  pyrites,  277 

—  pyrophorus,  277 

—  quinine  citrate,  555 

—  saccharate,  283 

—  somatose,  562 

—  sulphide,  277 

—  technical,  278 

—  \^triol,  282 
Irone,  503 
Isathionic  acid,  401 
Isatin,  547 
Isatinic  acid,  468 
Isindazole,  551 


600 


INDEX. 


Isobutane,  372 

Isobutyl  orthocresol  iodide,  491 

—  pyrrol,  545 
Isobutylene,  394 
Isobutyl  alcohol,  374 
Tsobutyric  acid,  374 
Isocarbocyclic  compounds,  326 
Isocholesterin,  526 
Isocinnamic  acid,  500 
Isocyanic  acid,  392 
Isocyanuric  acid,  392 
Isodiazoacetic  acid,  369,  512 
Isodiazo  compounds,  369,  512 
Isodulcite,  444 

Isodurene,  502 
Isoferulic  acid,  501 
Isologous  series,  399 
Isomerism,  80,  300,  466 

—  geometric,  303 

—  mixed,  468 

—  nucleus,  468 

—  optical,  303 

—  phjrsical,  303 

—  position,  303 

—  side-chain,  468 

—  stereochemical,  303 
Isomorphism,  23,  35 
Isonaphthol,  514 
Isonitrile,  391 
Isonitroso  compounds,  331 
Isopelletierine,  554 
Isopentyl  alcohol,  374 
Isophthalic  acid,  497 
Isopropyl  alcohol,  371 

—  benzene,  501 
Isoquinoline,  539 
Isosuccinic  acid,  425 
Isosulphocyanallyl,  438 
Isotonic,  20 
Isoxazole,  552 
Itabiryte,  277 
Itaconic  acid,  431 
Itrol,  431 

Ivory,  burnt,  187 

Jaborine,  553 
Jalapin,  528 
Jalapinolic  acid,  528 
Jalap  resin,  525 
Janus  green,  543 
Japaconitine,  559 
Japan  camphor,  523 


Jasper,  195 
Javelle  water,  205 
Jena  glass,  224 
Jervine,  559 
Juniper-oil,  521 

Kainite,  228 

Kalium,  201 

Kamalin,  532 

Kaolin,  252 

Kekul^'s  benzene  theory,  461 

Kelp,  142 

Keratin,  569 

Kermesite,  177 

Kermes,  181 

Kerosene,  342 

Ketobutyric  acid,  364 

Ketonamines,  372 

Ketone  alcohols,  337 

—  cleavage,  365 
Ketones,  371 
Ketonethyl  ester,  365 
Ketonic  acids,  337,  365 

—  acid  esters,  366 
Ketoses,  337,  447 
Kieserite,  228 
Kinetic,  65 

Kino  tannic  acid,  496 

Kjeldahl's  nitrogen  estimation,  311 

Knop-Hiifner's  urea  estimation,  411 

Kolbe's  synthesis,  492 

Kosin,  529 

Krypton,  182 

Kumys,  355 

Kussin,  529 

Kynurenic  acid,  540 

Kynurine,  540 

Labaraque  solution,  210 
Laccase,  571 
Lacmoid,  481 
Lactames,  469 
Lactalbumin,  563 
Lactase,  570 
Lactates,  406 
Lactic  acids,  406,  407 

series,  403 

Lactimes,  469 
Lactobiose,  455 
Lactones,  404 
Lactophenin,  485  " 
Lactose,  455 


INDEX. 


601 


Lactucerin,  526 
Lactyl,  404 

Lactyl  phenetidin,  485 
I.aevotartaric  acid,  428 
Lsevolactic  acid,  407 
Lsevulose,  452 
Lake  colors,  250 
Lampblack,  187 
Lanolin,  526 
Lanopalmitic  acid,  408 
Lapis  lazuli,  254 
Lard,  436 
Largin,  562 
Laughing-gas,  155 
Laurin,  377 
Laurie  acid,  377 
Laurinene  camphor,  523 
Lauthanum,  247 
Lauth's  violet,  544 
Lavender-oil,  521 
Law,  Avogadro's,  16 

—  Dalton's,  49 

—  Dulong-Petit's,  22 
• —  Faraday's,  75 

—  Gay-Lussac's,  15 

—  Gay-Lussac-Charles's,  15 

—  Guidberg-Waage's,  59 
• —  Henry-Dalton's,  49 

—  Hess's,  70 

—  Lavoisier-Laplace's,  69 
■ —  Mariotte-Boyle's,  15 

—  Neumann-Kopp's,  23 

—  periodic,  55 

—  stochiometric,  9 

—  of  the  conservation  of  matter,  10 

—  of  the  conservation  of  energy,  2 

—  of  constant  proportions,  10 

—  of  constant  angles,  34 

—  of  mass  action,  59 

—  of  multiple  proportion,  11 
- —  of  even  numbers,  314 

• —  of  thermoneutrality,  86 

—  of  simple  proportions  by  volume, 

12 
• —  of  volumes,  12 
Lead,  259 

—  acetate,  363 
basic,  363 

—  alkyls,  382 

—  alloys,  260 

—  ash,  259 

—  carbonate,  261 


Lead  carbonate,  basic,  261 

—  chromate,  269 

—  detection  of,  262 

—  glass,  224 

—  hydroxide,  260 

—  metaplumbate,  262 

—  nitrate,  260 

—  oleate,  440 

—  orthoplumbate,  262 

—  oxides,  260 

—  peroxide,  261 

—  phenylate,  474 

—  salts  of  the  fatty  acids,  437 

—  selenide,  131 

—  silicate,  261 

—  sulphate,  260 

—  sulphide,  261 

—  tannate,  495 

—  telluride,  132 

—  tetrachloride,  262 

—  vinegar,  363 

—  water,  364 
Lead-chamber  crystals,  129 

—  process,  128 
Lead  plaster,  437 
Lead-pencil  manufacture,  187 
Leather,  496,  569 

Le  Bel-van't  Hoff 's  theory,  304 

Leblanc's  soda  manufacture,  213 

Lecanoric  acid,  497 

Lecithalbumins,  565 

Lecithins,  434 

Legumelin,  563 

Legumin,  565 

Leipzig  yellow,  269 

Lepidine,  539 

Lepidolite,  215 

Leucaniline,  506 

Leucin,  376 

Leucinimide,  376 

Leucinic  acid,  408 

Leucomaines,  398 

Leuconuclein,  564 

Leuco  compounds,  506,  531 

Levulinic  acid,  371 

Lichen  acids,  497 

Lichenin,  459 

Lichesteric  acid,  497 

Liebermann's  reaction,  475^ 

Liebig-Pfliiger's    urea     estimation, 

411 
Light  blue,  507 


602 


INDEX, 


Light  green,  507 

—  oil,  473 

—  metals,  198 
Lignin,  458 
Lignoceric  acid,  377 
Lignose,  456 
Lignosiilphite,  456 
Ligroin,  341 
Lime,  219 

—  burnt,  219 

—  slaked,  220 

—  hydraulic,  220 
Lime-light,  Drummond's,  113 
Limestone,  223 
Lime-water,  220 

Lime  tuff,  224 

Limit  hydrocarbons,  340 

halogen  compounds  of,  348 

Limonene,  522 

Limonite,  277 

Linalool,  444 

Linde's  regenerative  apparatus,  41 

Liniments,  437 

Linnseite,  285 

Linoleic  acid,  445 

Linseed-oil,  436 

Lipanin,  436 

Lipase,  571 

Lipochromes,  531 

Lipowitz's  metal,  264 

Liqueurs,  355 

Liquids,  general  properties,  37 

Liter-weight  of  gases,  42 

Litharge,  260 

Lithium,  215 

—  carbonate,  216 

—  quinate,  496 

—  phosphate,  216 

—  salicylate,  492 
Litmus,  493 

—  as  indicator,  87 

—  pigment,  493 
Lithofracteur,  458 
Lithopone,  232 
Liver-starch,  459 
Liver  of  sulphur,  204 
Loam,  253 
Lobelline,  559 
Loew's  formose,  350 
Lollingite,  170 
Loretin,  540 
Lotoflavin,  384 


Lotusin,  384 
Lubricating-oil,  342 
Lugol's  solution,  142 
Luminosity  of  flame,  92 
Lupeol,  526 
Lupetidines,  538 
Lupinotoxin,  572 
Luteines,  532 
Luteocobaltic  salts,  287 
Luteolin,  542 
Lutidine,  538 
Lycin,  369 
Lycopodine,  559 
Lyddite,  479 
Lyons  blue,  507 
Lysidin,  551,  398 
Lysin,  376 
Lysitol,  491 
Lysol,  491 
Lyxonic  acid,  444 
Lyxose,  444 

m-compounds,  468 
Madder,  516 

—  lakes,  517 
Magdala  red,  543 
Magnalium,  228 
Magnesia,  228 

—  mixture,  169 
Magnesite,  227 

—  spar,  229 
Magnesium,  227 

—  alk>les,  382 

—  aluminate,  251 

—  amalgam,  243 

—  aurate,  291 

—  carbonate,  229 

—  chloride,  229 

—  citrate,  effervescent,  431 

—  compounds,  228 

—  detection  of,  230 

—  group,  227 

—  hydroxide,  228 

—  oxide,  228 

—  phosphate,  169 

—  silicate,  227 

—  sulphate,  229 
Magnetic  iron-ore,  277 

—  pyrites,  277 
Majolica  ware,  253 
Maklurin,  505 
Malachite,  233 


INDEX. 


603 


Malachite,  green,  507 
Maleic  acid,  427 
MaUein,  572 
Malates,  426 
Malic  acid,  426 
Mallotoxin,  532 
Malonic  acid,  423 

diethyl  ester,  424 

structure  of,  421 

Malonyl,  421 

—  urea,  414 
Malt,  356 

—  sugar,  455 

—  wines,  356 
Maltase,  570 
Maltobiose,  455 
Maltodextrin,  459 
Maltose,  455 
Manchester-brown,  510 
Mandelic  acid,  498 

nitrile  diglucose,  498 

Manganates,  275 
Manganese,  273 

—  alum,  252 

—  bronzes,  273 

—  compounds,  273 

—  copper,  273 

—  detection  of,  277 

—  dioxide,  275 

—  heptoxide,  276 

—  peroxide,  275 
Manganic  acid,  275 

—  carbonate,  275 

—  compounds,  274 

—  chloride,  274 

—  hydroxide,  274 

—  manganite,  274 

—  oxide,  274 

—  sulphate,  274 

—  sulphide,  273 
Manganin,  288 
Manganite,  273 
Manganous  acid,  275 

—  carbonate,  274 

—  chloride,  274 

—  hydrocyanic  acid,  387 

—  hydroxide,  273 

—  manganic  oxide,  274 

—  oxide,  273 

—  sulphate,  274 

—  sulphide,  273 
Mannite,  445 


Mannite  nitrate,  446 
Mannonic  acid,  446 
Mannose,  446 
Marble,  223 
Marcasite,  277 
Mariotte's  law,  15 
Marl,  253 

Marsh  apparatus,  172 
Marsh's  arsenic  test,  177 
Marsh  gas,  346 
Martin  steel,  281 
Martius-yellow,  515 
Mascagnine,  217 
Mash  of  beer,  356 
Mass  action,  60 
Massicot,  260 

Matter,  maintenance  of  the  quan- 
tity. 9 
Matricaria  camphor,  523 
Mauvein,  543 

Meerschaum,  227  ^ 

Mechanics,  chemical,  60 
Meconic  acid,  541 
Meconinic  acid,  497 
Melamin,  392 
Melanines,  546 
Melampyrite,  446 
Melene,  394 
Melezitose,  456 
Melibiose,  455 
Melinit-,  479 
Melilolic  acid,  502 
Melissic  acid,  377 
Melissyl  alcohol,  376 
Melitose,  456 
Melitriose,  456 
Mellitic  acid,  187,  503 
Mellite,  503 
Melting-point,  35,  321 
Membrane,  semipermeable,  48 
Mendius's  reaction,  378 
Menthene,  524 
Menthon,  524 
Menthol,  524 
Menyanthin,  528 
Menyanthol,  528 
Mercaptals,  351 
Mercaptans,  332,  351 
Mercaptides,  332 
Mercaptols,  371 
Mericyl  alcohol,  376 
Mercury,  242 


604 


INDEX. 


Mercury  alkyls,  382 

—  alloys,  242 

—  detection  of,  247 

—  fulminate,  391 

—  peptone,  568 

—  urea,  411 
Mercuric  acetamide,  367 

—  acetonitrile,  391 

—  ammonium  chloride,  246 

—  chloride,  245 

—  compounds,  244 

—  cyanide,  386 

—  hydroxide,  245 

—  iodide,  243 

—  nitrate,  247 

—  oxalate,  245 

—  oxide,  244 

—  phenylate,  474 

—  salicylate,  492 

—  sulphate,  246 

—  sulphide,  245 

—  sulphocyanate,  393 

—  thiocyanate,  393 
Mercurous-ammonium  chloride,  244 
nitrate,  244 

Mercurous  chloride,  243 

—  compounds,  243 

—  hydroxide,  243 

—  hydrozoate,  151 

—  iodide,  244 

—  nitrate,  244 

—  oxide,  243 

—  sulphide,  243 

—  tannate,  495 
Mercurial  plaster,  437 
Mesaconic  acid,  431 
Mesitol,  474 

Mesitylene,  371,  472,  499 
Mesitylenic  acid,  499 
Mesityl  oxide,  371 
Mesorcin,  474 
Mesotartaric  acid,  428 
Mesoxalic  acid,  434 
Mesoxaluric  acid,  414 
Mesoxalyl  urea,  414 
Meta-compounds,  467 
Meta-arsenious  acid,  175 
Meta-bismuth  hydroxide,  264 
Metabismuthic  acid,  264 
Metacrolein,  439 
Metaglobulin,  564 
Metalbumin,  567 


Metaldehyde,  360 
Metamerism,  301 
Metantimonic  acid,  180 
Metaplumbates,  262 
Metaphosphates,  170 
Metaphosphric  acid,  169 
Metarsenic  acid,  175 

anilide,  485 

Metastannate,  257 
Metastannic  acid,  257 
Metatartaric  acid,  428 
Metauric  acid,  291 
Metallic  alcoholates,  343 

—  alkyls,  381 

—  cyanides,  386 

—  organic  compounds,  331 ,  381 
Metalloids,  95 

Metals,  95,  198 

—  base,  200 

—  classification  of,  198 

—  colloidal,  199 

—  compounds  with  alcohol  radical^ 

381 

—  cyanogen  compounds  of,  385 

—  hydrogen  compounds  of,  200 

—  heavy,  199 

—  light,  198 

—  noble,  200 

—  occurrence  of,  200 

—  preparation  of,  201 

—  properties  of,  198 

—  soluble  in  water,  199 
Meteoric  iron,  277 
Methsemoglobin,  566 
Methanal,  349 
Methane,  346 
Methenyl,  431 
]\Iethine  group,  537 
Methoxyl,  329 
Methoxylanilines,  485 
Methoxylbenzoic  acid,  492 
Methyl,' 328 
Methylacetanilide,  485 

—  aclohol,  349 

—  aldehyde,  349 

—  amido-acetic  acid,  369 

—  amido  cresol,  491 

—  amido  oxybenzoate,  492 

—  amine,  379 

—  aniline,  484 

—  arbutin,  527 

—  arsino,  380 


INDEX. 


605 


Methyl  arsine  oxide,  380 

—  benzene,  486 

—  benzoic  acids,  497 

—  benzyl  compounds,  497 

—  chloride,  347 

—  cyanide,  390 

—  dihydroimidazole,  551 

—  dioxy  anthraquinone,  517 

—  ethylamine,  378 

—  ethyl  ether,  359 

—  fumaric  acid,  431 

—  green,  507 

—  guanidine,  412 
acetic  acid,  412 

—  homopyrocatechin,  493 

—  hydride,  346 

—  hydroxide,  349 

—  indol,  548 

—  inosite,  483 

—  isopropyl  benzene,  503 
phenanthrene,  518 

—  maleic  acid,  431 

—  mercaptan,  351 

—  orange,  510 

—  oxycinnamic  acids,  501 

—  pentose,  444 

—  pelletierine,  554 

—  phenol,  475 

—  phenylketone,  498 

—  phosphine,  380 

—  phthalic  acid,  499 

—  protocatechuic  aldehyde,  494 

—  propyl  benzenes,  503 
phenols,  503 

—  pyridine,  538 

—  pyrogallol,  474,  494 

—  quinoline,  539 

—  salicylate,  492 

—  salicylic  acid,  492 

—  succinic  acid,  425 

—  sulphonal,  372 

—  sulphide,  351 

—  sulphur  ether,  351 
• —  theobromine,  416 

—  tetraoxyanthraquinone,  517 

—  trioxyanthraquinone,  517 

—  urea,  413 

—  violet,  507 

—  xanthine,  416 

—  xanthogenate,  408 
Methylene,  328 

—  blue,  544 


Methylene  chloride,  396 

—  green,  544 

—  iodide,  396 

—  succinic  acid,  431 
Methylenitan,  450 
Metol,  491 

Meyer's   vapor  density  determina- 
tion, 315 
Miazines,  542 
Miazoles,  550 
Mica  schist,  248 
Michler's  ketone,  505 
Microcosmic  salt,  217 
Middle-oil,  473 
Mietose,  563 
Milk  casein,  565 
Milk  glass,  225 

—  of  lime,  220 

—  of  sulphur,  121 

—  sugar,  455 
Milky  quartz,  195 
Millon's  reagent,  247,  562 
Mineral  chama?loon,  275 
Mineral  fat,  342 

—  waters,  116 

—  wax,  342 
Minesite,  206 
Minium,  262 
Mirror  isomers,  305 
Mispickel)  170 

Mitscherlich's    detection    of    phos- 
phorus, 164 
Mixed  crystals,  49 
Mixtures,  physical,  46 

—  eutectic,  50 

—  isomorphic,  49 
Modifications,  optical,  39 

—  racemic,  39 
Mohr's  salts,  283 
Molasses,  454 
Moldering,  326 
Mol,  36 

—  volume,  43 
Molecular  aggregation,  32 

—  compounds,  30 

—  formula?,  empirical,  26,  317 

determination  of,  313 

rational,  26,  317 

—  heat,  23 

—  structure,  investigations  of,  317 

—  refraction,  38 

—  weight,  14 


606 


INDEX. 


Molecular  weight,  determination,  14 

—  volume,  36 
Molecule,  14 

—  asymmetric,  307 

—  monatomic,  22 

—  symmetric,  306 
Molybdenite,  271 
Molybdenum,  271 

—  trioxide,  271 

—  trisulphide,  271 
Molybdic  acid,  271 
Monamines,  330 
Monazite,  248 

Monobrom  succinic  acid,  424 
Monochloracetic  acid,  368 
Monochlormethane,  347 
Monoclinic  crystal  system,  34 
Monosaccharides,  451 
Monoses,  451 

Monosodium  glycolate,  399 
Monosulphocarbonic  acid,  192,  408 
Monosymmetric  crystal  system,  34 
Mordants,  530 

Moringa,  541 
Morin  tannic  acid,  496 
Morphine,  556 
Morphindiacetic  ester,  556 
Morpholin,  544 
Mortar,  220 
Mosaic  gold,  258 
Moss  starch,  459 
Mother-liquor,  52 
Mucic  acid,  447 
Mucilage,  460 
Mucins,  566 
Mucinogens,  566 
Mucedin,  567 
Mucinoids,  567 
Mucoids,  567 
Mulberry  calculi,  422 
Multirotation,  452 
Muntz  metal,  235 
Murexide,  415 

—  test,  419 
Muriatic  acid,  136 
Muscarine,  380,  398,  544 
Muscle  albumin,  563 

—  globulin,  564 
Musk,  artificial,  503 
Mustard-oils,  438 
Mutase,  563 
Mutton  tallow,  436 


Mycose,  455 
Mydaleine,  398 
Mydatoxine,  398 
My  din,  398 
Myogen,  563 

—  fibrin,  567 
Myosin,  564 

—  fibrin,  567 
Myricyl  alcohol,  376 

—  paimitate,  376 
Myristic  acid,  377 
Myristicin,  377 
Myristicol,  524 
Myronic  acid,  438 
Myrosin,  571 
Myrrha,  525 
Mytilotoxine,  398 

Nahrstoff  Heyden,  563 
Naphthacene,  513 
Naphthalene  azo  dyes,  510 
Naphthalene,  513 

—  blue,  510 

—  dyes,  515 

—  sulphonic  acid,  514 

—  yellow,  515 
Naphthazarine,  515 
Naphthenes,  463 
Naphthols,  514 
Naphthol  benzoate,  515 

—  ethyl  ether,  515 

—  phenazine,  543 

—  sulphonic  acids,  515 

—  yellow,  515 
Naphtoquinone,  515 
Naphtoquinoline,  537 
Naphthylamine,  514 
Naples  red,  253 
Narceine,  556 
Narcotine,  556 
Nascent  state,  9,  17 
Nataloin,  517 
Natrium,  209 

Neighboring  substitution  products, 

469 
Neodymium,  247 
Neon,  182 
Nemst  light,  228 
Nerolin,  515 
Nessler's  reagent,  246 
Neumann-Kopp's  law,  23 
Neuridine,  398 


INDEX. 


607 


Neurine,  380 
Neusidonol,  493 
Neutralization,  85 
Neutralization,  heat  of,  68,  86 
Niccolite,  170,  287 
Nickel,  287 

—  alloys,  288 

—  carbonyl,  189 

—  coins,  288 

—  compounds,  288 

—  detection  of,  288 

—  glance,  287 
Nickelin,  288 
Nickelous  compounds,  288 

—  hydroxide,  288 

—  oxide,  288 

—  plating,  287 

—  salts,  288 

—  sulphide,  288 
Nickelic  compounds,  288 

—  hydroxide,  288 

—  oxide,  288 

—  salts,  288 
Nicotine,  554 
Nicotinic  acid,  539 
Nigrosine,  543 
Nile  blue,  544 
Niobium,  265 
Nirvanin,  493 
Nitragin,  147 
Nitramines,  330 
Nitrates,  161 
Nitration,  160 
Nitric  acid,  158 

detection  of,  161 

fuming,  160 

red,  160 

Nitric  anhydride,  158 

—  oxide,  156 
Nitrides,  147 
Nitrification,  161 
Nitrile  bases,  330  , 
Nitriles,  330,  390,  421  J 
Nitrites,  157 
Nitrogen,  146 

—  bases,  377 

—  bridge,  557 

—  bromide,  152 

—  chloride,  152 

—  compounds  with  boron,  184 

metals,  147 

halogens,  152 


Nitrogen   compounds  with  carbon, 
193,  381 

oxygen,  154 

hydrogen,  147 

—  di-iodide,  1-52 

—  dioxide,  158 

—  estimation  in  organic  compounds, 

311 

—  group,  145 

—  iodide,  152 

—  mixture  with  oxygen,  152 

—  oxide,  156 

—  pentoxide,  158 

—  stereochemistry  of,  308 

—  tetroxide,  158 
Nitro-,  96 

Nitro-aceton  nitrile,  390 
Nitro-benzene,  478 
Nitro-chloroform,  349 
NitFo- compounds,  464 
Nitro-diphenyls,  504 
Nitro-dyes,  515 
Nitro-erythrite,  443 
Nitro-ethane,  356 
Nitro-form,  349 
Nitroglycerine,  434 
Nitro  groups,  464 
Nitronaphthalene,  514 
Nitrophenols,  479 
Nitrophenyl  propiolic  acid,  502 
Nitroprusside  compoimds,  389 
Nitrosamines,  330 

Nitroso  compounds,  330 

—  group,  330 
Nitrosophenols,  481 
Nitrosulphonic  acid,  128 
Nitrosyl  chloride,  160 
Nitrosylic  acid,  155 
Nitrosylsulphuric  acid,  128,  157 
Nitrotoluene,  487 

Nitrous  acid,  157 

—  anhydride,  156 

—  oxide,  155 
Nitryl  chloride,  160 
Nobel's  powder,  434 

—  explosive  oil,  434 
Nomenclature,  326,  471,  535 

—  of  acids,  97 

—  of  bases,  99 

—  of  binary  compounds,  96 

—  international,  337 

—  of  radicals,  96 


608 


INDEX. 


Nomenclature  of  salts,  99 

—  ternary,  etc.,  compounds,  97 
Nonane,  340 
Non-conductor,  74 
Non-metals,  95 

Nonoses,  448,  451 
Nonvl  acetate,  381 

—  alcohol,  381 

—  chloride,  381 
Nordhausen  oil  of  vitriol,  129 
Normal  volume,  42 
Nosophene,  508 

Nucleic  acids,  564 
Nucleins,  564 
Nuclein  bases,  415 
Nucleoalbumins,  564 
Nucleoproteids,  564 
Nucleus  isomerism,  468 
Nut-oil,  435 
Nutrose,  562 

o-compounds,  468 

Oak-gall  tannic  acid,  496 

Oak  tannic  acid,  496 

Obsidian,  248 

Ochre,  253 

Octane,  340 

Octoses,  448 

Octyl  alcohol,  normal,  375 

—  acetate,  361 
Octylene,  394 
Octylic  acids,  376 
Q^]nanthic  ether,  376 
CErstedite,  263 
Oiazines,  542 
Oiazoles,  550 

Oil  of  lemons,  521 

—  of  the  Dutch  chemists,  397 

—  of  cinnamon,  500 

—  of  mirbane,  478 

—  of  vitriol,  127 
Nordhausen,  129 

—  of  wintergreen,  521 
Oils,  435,  436 

—  drying,  435 

—  ethereal,  521 

—  non-drving,  435 
Oil-sugar,^  521 
Oleates,  440 
Olefines,  394 

—  amines,  397 

—  halogen  compounds,  396 


Oleic  acid,  440 

series,  439 

Olein,  435 
Oleomargarine,  435 

—  oil,  435 
Olibanum,  525 
Olivin,  22*7 
Olive-oil,  436 
Onion-oil,  521 
Onocerin,  526 
Ononetin,  528 
Onon,  528 
Ononin,  528 
Onyx, 195 
Oochlorin,  545 
Oocyanin,  545 
Oorhodin,  545 
Opal,  195 
Opalisin,  563 
Opianic  acid,  497 
Opodeldoc,  437 

Optical    behavior   of    the    C   com- 
pounds, 38,  303 
Orcein,  493 
Orcin,  493 

—  carbonic  acid,  496 
Ores,  202 

Orexin,  543 

Organic,  4 

Organized,  4 

O  nithin,  375 

Ornithuric  acid,  489 

Orpiment,  176 

Orsellic  acid,  497 

Orseille  dyes,  493 

Ortho  compounds,  468 

Orthoform,  493 

Orthophosphoric  acid,  168 

Orthostannic  acid,  257 

Osazones,  450 

Oscine,  558 

Osones,  450 

Osmic  acid,  295  * 

Osmium,  295 

—  chlorides,  295 

—  lamp,  295 

—  tetraoxide,  295 
Osmosis,  46 
Osotriazole,  551 
Ossein,  569 
Osteoliths,  162 
Ovalbumin,  563 


INDEX. 


609 


Ovomucoid,  567 
Ovovittelin,  565 
Oxalates,  423 
Oxalic  acid,  422 
Oxalic  acid  series,  420 
Oxalonitrile,  423 
Oxaluric  acid,  414 
Oxalyl,  421 

—  urea,  414 
Oxamic  acid,  423 
Oxamide,  423 
Oxanthin,  545 
Oxazine,  544 

—  dyes,  544 
Oxazole,  552 
Oxazones,  544 
Oxazone  dyes,  544 
Ox-bile  mucin,  565 

Oxidation   zone   of   the   blast-fur- 
nace, 281 

—  flame,  92 
Oxidation,  108 
Oxides,  96,  108 
Oxidizing  agents,  321 
Oximido  compounds,  331 
Oximes,  331 

Oxonium  compounds,  541 
Oxygen,  106 

—  active,  110 

—  estimation  in  organic  compounds, 

312 

—  group,  106 
Oxy acids,  98 

Oxy acetic  acid,  368,  405 
Oxyaldehydes,  402 
Oxyammonia,  150 
Oxyazines,  544 
Oxyazo  compounds,  510 
Oxybenzene  compounds,  479 
Oxybenzoic  acids,  492 
Oxybenzyl  compounds,  491 
Oxybutyl  aldehyde,  360 
Oxybutyric  acids,  403 
Oxycamphor,  523 
Oxycaproic  acids,  403 
Oxy  cellulose,  457 
Oxycholine,  380 
Oxycinnamic  acid,  501 

—  anhydride,  501 
Oxycoumarin,  501 
Oxyethyl  sulphonic  acid,  401 
Oxyfatty  acids,  403 


Oxyformic  acid,  408 
Oxygenase,  571 
Oxyhaemoglobin,  566 
Oxyhydrocoumaric  acid,  502 
Oxyhydroquinone,  482 
Oxyhydrogen  blowpipe,  112 
Oxymalonic  acid,  424,  434 
Oxymesitylenic  acid,  476 
Oxymethyl-benzyl  compounds,  493 

—  benzoic  acids,  497 
Oxyneurine,  369 
Oxyoleic  acid,  441 
Oxyphenylamidoacetic  acid,  498 
Oxyphenylacetic  acid,  498 
Oxyphenylamidopropionic  acid,  502 
Oxyphenylpropionic  acid,  476,  502 
Oxyphthalic  acids,  496 
Oxypropanetricarbonic  acid,  430 
Oxypropionic  acids,  406 
Oxyprotosulphonic  acid,  561 
Oxypurin,  415 

Oxy  pyridines,  538 
Oxypyrone,  541 

—  carbonic  acid,  541 
Oxyquinolines,  540 
Oxyquinoline  carbonic  acid,  540 
Oxysalicylic  acids,  494 
Oxysuccinic  acid,  426 
Oxysulphuric  acid,  131 
Oxytoluene  compounds,  491 
Oxytolyhc  acids,  476,  496 
Oxytropine,  558 

Oxyvaleric  acids,  403 
Oxyxylenes,  496 
Oyster-shells,  223 
Ozocerite,  342 
Ozone,  110 

p-compounds,  468 
Palladic  chloride,  294 
Palladium,  294 

—  black,  294 

—  hydride,  294 
Palladous  chloride,  294 

—  iodide,  294 
Palmitic  acid,  377 
Palmitin,  377,  435 
Pan  acid,  128 

—  stone,  210 
Pancreatin,  570 
Paonines,  508 
Papain,  570 


610 


INDEX. 


Papaverine,  556 
Papayotin,  570 
Paper,  556 

Para  compounds,  468 
Parabanic  acid,  414 
Paracholesterin,  526 
Paraffins,  340 

—  halogen  compounds,  348 
Paraffine-oil,  342 
Paraformaldehyde,  350 
Paraglobulin,  564 
Paraldehyde,  360 
Paralactic  acid,  407 
Paralbumin,  567 
Paraleucaniline,  506 
Paramucin,  567 
Paranucleic  acids,  565 
Paranucleins,  565 
Paranucleo  albumins,  565 
Paranucleo  proteids,  565 
Pararosaniline,  506 

Par*  saccharic  acid,  528 
Paraxanthine,  416 
Parchment  paper,  457 
Parisian  blue,  507 

—  yellow,  269 

—  violet,  507 
Parke's  method,  239 
Partial  pressure,  49 
Partinium,  249 
Parvoline,  538 
Passivity,  278 
Patina,  237 

Pattinson's  method,  239 
Pearis,  223 

Pear-oil,  374 
Peat,  188 
Pectase,  460,  571 
Pectin  e  acids  460 

—  bodies,  460 
Pectose,  460 
Pelletierine,  554 
Pentamethylene,  464 
Pentamethyl  benzene,  503 
Pentamine,  397 
Pentamethylendiamine,  398 
Pentamethylphenol,  474 
Pentane,  340 
Pentaoxybcnzene,  482 
Pentasilicates,  197 

Penta  silicic  acid,  197 
Penta  thionic  acid,  124 


Penthiophene,  536 
Pentine,  441 
Pentosanes,  444 
Pentoses,  444,  448 
Pentylene,  394 
Peppermint-oil,  521 
Pepsin,  570 
Peptones,  568 
Peptotoxin,  572 
Per-,  99 

Perboric  acid,  185 
Perbromic  acid,  141 
Percarbonates,  192 
Percarbonic  acid,  192 
Perchlorates,  139 
Perchloric  acid,  139 
Perchromic  acid,  269 
Perhydroretene,  518 
Periodates,  144 
Per-iodic  acid,  144 
Periodic  system,  55 
Perkins's  reaction,  500 
Permanent  white,  226 
Permanganates,  276 
Permanganic  acid,  276 

—  anhydride,  276 
Peronin,  556 
Perosmic  acid,  295 

—  anhydride,  295 
Peroxides,  97 

Peroxyprotsulphonic  acid,  561 
Perseit,  447 
Persulphates,  131 
Persulphuric  acid,  131 
Peruol,  489 

Peru  balsam,  501 
Peruscabin,  489 
Petalite,  215 
Petroleum,  341 

—  benzine,  341 

—  ether,  341 
Petrolic  acids,  464 
Pettenkofer's  reaction,  370 
Pharaoh's  serpent,  393 
Phaseomannite,  483 
Phase  rule,  64 

Phases,  64 
Phellandren,  522 
Phenacetine,  485 
Phenaceturic  acid,  490 
Phenacite,  227 
Phenanthrene,  518 


INDEX. 


611 


Phenanthrenquinone,  518 
Phenazine,  543 
Pheneti  dines,  485 
Phenetol,  480 

—  carbamide,  480 
Phenetyldianisyl  guanidine,  486 
PhenocoU,  485 

Phenolin,  491 
Phenol,  479 

—  aldehyde,  491 

—  alcohols,  491 

—  blue,  486 

—  ethyl  ether,  480 

—  methyl  ether,  480 
Phenolphthalein,  508 

—  indicator,  87 

Phenolsulphonic  acids,  464,  480 
Phenols,  466,  474 

—  dihydric,  474 

—  polyhydric,  474 
Phenolic  acids,  477 
Phenoxazine,  544 
Phenthiazine,  544 
Phentriazine,  543 
Phenyl,  471 

—  acetic  acid,  476,  498 

—  acetylene,  472 

—  acrylic  acid,  501 

—  alanin,  502 

—  allyl  alcohol,  501 

—  amidopropionic  acid,  502 

—  amine,  484 

—  benzopyrone,  542 

—  butylene,  514 

—  carbonic-acid  ester,  475 

—  carbylamine,  347 

—  dihydroquinazoline,  543 

—  dimethyl  pyrazolon,  551 

—  ether,  480 

—  ethylene,  472 

—  ethyl  alcohols,  475 

—  formanilide,  485 

—  formic  acid,  488 

—  glycocoll,  547 

—  glycollic  acid,  498 

—  hydrazin,  486 

—  hydroxide,  479 

—  lactic  acid,  477 

—  oxypropionic  acid,  502 

—  propiolic  acid,  502 

—  propionic  acid,  476,  502 

—  propyl  alcohol,  475,  502 


Phenyl  salicylate,  492 

—  sulphuric  acid,  480 

—  tolyl,  504 
Phenylene  blue,  486 

—  brown,  510 

—  diamine,  485 
Phillipium,  247 
Phlobaphenes,  496 
Phloretic  acid,  502 
Phloretin,  528 
Phlorhizin,  528 
Phloroglucin,  482 

—  carbonic  acid,  476 
Phloroglucite,  482 
Phloxin,  508 
Phoron,  371 
Phosgene  gas,  190 
Phosgenite,  132 
Phosphates,  162,  169 
Phosphides,  163 
Phosphine,  165 
Phosphines,  380 
Phosphin,  540 
Phosphine  dyes,  540 
Phosphites,  167 
Phosphonium  bases,  380 

—  compounds,  165 

—  iodide,  165 
Phosphocamic  acid,  568 
Phosphomolybdic  acid,  271 
Phosphoreted  hydrogen,  165 
solid,  166 

liquid,  166 

Phosphoric  acid,  tribasic,  168 

—  anhydride,  167 
Phosphorites,  262 
Phosphorous  acid,  167 

—  anhydride,  167 
Phosphorus,  161 

—  black,  164 

—  bromides,  166 

—  bronze,  235 

—  chlorides,  166 

—  compounds,  165-166 

—  detection  of,  164 

—  estimation,  310,  312 

—  hexoxide,  167 

—  iodides,  166 

—  monoxide,  166 

—  oxy  chloride,  166 

—  pentachloride,  166 

—  pentasulphide,  170 


612 


INDEX. 


Phosphorus  pentoxide,  167 

—  red,  164 

—  tetroxide,  166 

—  trichloride,  166 

—  trioxide,  167 

—  trisulphide,  170 
Phosphorus  salt,  217 
Phosphotungstic  acid,  271 
Photochemistry,  91 
Photography,  241 
Phthalazine,  543 
Phthalemes,  508 
Phthahc  acids,  497 

—  anhydride,  497 
PhthaUmide,  497 
Phthalyl  alcohol,  497 
Phycite,  443 
Phyllocyanin,  545 
Phylloporphyrin,  545 
Phylloxanthine,  545 
Physics,  1,  2 
Physostigmine,  559 
PhytoglobuUn,  565 
Phytosterin,  526 
Phytovitellin,  565 
Piazines,  542 
Piazoles,  550 
Piazthiol,  552 
Picene,  513 
Picoline,  538 
Picrate  powder,  479 
Picric  acid,  479 
Picroaconitine,  558 
Picrocarmine,  518 
Picrotin,  529 
Picrotoxinin,  529 
Picrotoxin,  529 
Pictet's  chloroform,  347 
Pigments,  adjective,  530 

—  artificial,  531 

—  indifferent,  530 

—  organic,  530 

—  substantive,  530 
Pilocarpidine,  553 
Pilocarpine,  553 
Pimaric  acid,  525 
Pimellic  acid,  420 
Pimpinellin,  529 
Pinnulin,  552 
Pinakones,  372,  400 
Pinene,  522 
Pinenhydrochloride,  522 


Pine  resin,  525 
Pinite,  483 
Pink  salt,  257 
Pipecolines,  538 
Piperic  acid,  501 
Piperidin,  538,  539 
Piperine,  553 
Piperazin,  398 
Piperonal,  494 
Pitch,  324 
Pittacal,  508 
Plane  symmetry,  308 
Planes  of  symmetry,  34 
Plant  albumins,  563 

—  bases,  552 

—  fibrin,  567 

—  globulin,  565 

—  gums,  460 

—  jellies,  460 

—  wax,  375 
Plasmon,  562 
Plasters,  437 
Platinamines,  293 
Platmates,  293 
Platinic  chloride,  293 

—  hydroxide,  293 

—  oxide,  293 

—  sulphide,  293 
Platinous  chloride,  293 

—  hydroxide,  293 

—  oxide,  293 
Platinum,  292 

—  amalgam,  243 

—  asbestus,  126 

—  black,  292 

—  colloidal,  292 

—  detection  of,  294 

—  group,  288 

—  metals,  289 

—  ores,  289 

—  spongy,  292 
Platosamines,  293 
Pleonaste,  251 
Plum  brandy,  255 
Plumbago,  187 
Plumbates,  262 
Plumbic  anhydride,  261 

—  acids,  261 

—  chloride,  262 

—  hydroxide,  263 

—  oxide,  261 

—  sulphate,  262 


INDEX. 


613 


Plumbous  carbonate,  261 

—  chloride,  260 

—  hydroxide,  260 

—  iodide,  260 

—  nitrate,  260 

—  oxide,  260 

—  silicate,  261 

—  sulphate,  260 

—  sulphide,  261 
Plumbum,  259 
Plum  gum,  460 
Podophyllin,  525 
Podophyllotoxin,  529 
Poirier's  blue,  507 
Polarization,  38 
Polonium,  272 
Pollucite,  215 

Poly  acids,  197 
Poly  amines,  483 
Polychroit,  532 
Polychromic  acids,  268 
Polycrase,  248 
Polymerization,  320 
Polymerism,  300 
Polymethylene,  463 
Polymorphite,  259 
Polymorphic,  35 
Polysaccharides,  456 
Polysilicic  acids,  197 
Polysulphides,  204 
Polyterpenes,  522 
Polythionic  acids,  124 
Ponceau,  510 
Poppy-oil,  436 
Populin,  528 
Porcelain  clay,  253 
Porphyry,  248 
Position  isomerism,  302 
Potable  water,  117 
Potato-starch,  459 
Potash,  207 

—  fertilizers,  202 

—  soaps,  437 

—  water-glass,  208 
Potassium,  201 

—  acetate,  363 

—  acid  tartrate,  429 

—  alum,  252 

—  antimonous  tartrate,  430 

—  arsenite,  207 

—  aurate,  291 

—  auro-cyanide,  290 


Potassium  bicarbonate,  208 

—  bioxalate,  423 

—  bitartrate,  429 

—  bisulphate,  206 

—  bromide,  204 

—  yellow  chromate,  269 

—  red  chromate,  269 

—  carbon  monoxide,  202 

—  carbonate,  207 

—  caustic,  203 

—  chlorate,  205 

—  chloride,  204 

—  chromium  sulphate,  267 

—  compounds,  203 

—  cyanate,  392 

—  cyanide,  386 

—  cobaltic  nitrite,  287 

—  detection  of,  208 

—  dichromate,  269 

—  ethybcanthogenate,  408 

—  ferrate,  284 

—  ferricyanide,  389 

—  ferriferrocyanide,  389 

—  ferrocyanide,  387 

—  ferro-ferrocyanide,  389 

—  hydride,  203 

—  hydrate,  203 

—  hydroxide,  203 

—  hydrosulphide,  204 

—  hypochlorite,  205 

—  iodide,  205 

—  magnesium  sulphate,  229 

—  manganate,  275 

—  manganite,  275 

—  nitrate,  206 

—  nitrite,  207 

—  osmate,  295 

—  oxalate,  423 

—  perchlorate,  205 

—  permanganate,  376 

—  persulphate,  206 

—  phenylsulphate,  480 

—  picrate,  209 

—  platinum  chloride,  293 

—  platinate,  293 

—  polysulphides,  204 

—  pyrosulphate,  206 

—  quadroxalate,  423 

—  silicate,  208 

—  silicofluoride,  195 

—  sodium  tartrate,  429 

—  sulpharsenite,  177 


614 


INDEX. 


Potassium  sulpharsenate,  177 

—  sulphate,  206' 

—  sulphide,  203 

—  sulphocyanide,  393 

—  sulphostannate,  258 

—  sulphuret,  203 

—  tartrate,  429 

—  tetraoxalate,  423 

—  thiocyanate,  393 

—  trisulphide,  204 

—  uranate,  272 
Pottery,  253 

Power  of  refraction,  38 
Praseodymium,  247 
Prehnitic  acid,  502 
Prehnitol,  502 
Preparing  salt,  257 
Pressure,  critical,  41 

—  osmotic,  19,  48 
Primrose,  508 
Primary,  329 

Principle  of    variable    equilibrium, 
62 

—  of  coexistence,  67 

—  of  maximum  work,  70 
Printers'  ink,  187 
Process,  basic,  281 

—  analytical,  7 

—  synthetical,  7 
Processes,  chemical,  6 
Proustite,  238 
Propane,  370 

Propantricarbonic  acid,  431 
Propargyl,  444 

—  alcohol,  444 
Propargyllic  acid,  445 
Propenyl,  431 

—  alcohol,  432 
Propeptones,  568 
Properties,  additive,  30 

—  colligative,  20 

—  constitutive,  30 
Propine,  441 
Propiolic  acid,  445 
Propionic  acid,  370 
Proportions,  constant,  10 

—  multiple,  1 1 
Propyl,  328,  370 

—  aldehyde,  370 

—  alcohol.  370 

—  benzene,  501 

• —  piperidin,  539 


Propylene,  394 
Propylenglycol,  399 
Protagons,'527 
Protamins,  561 
Protargol,  562 
Proteids,  563 
Proteins,  560 
Proteinoids,  569 
Proteoses,  568 
Protocatechuic  acid,  494 

—  alcohol,  493 

—  aldehyde,  493 

—  dimethyl  ester,  494 
Protocetraric  acid,  497 
Protone,  561 
Protoplasmin,  562 
Protoveratrine,  559 
Prussian  blue,  388 
Prussiate,  yellow,  387 

—  red,  389 

Pseudo  aconitine,  558 

—  butylene,  394 

—  cumene,  499 

—  conhydrine,  554 

—  isomerism,  300 

—  jervine,  559 

—  mucm,  567 

—  ononin,  528 

—  pelletierine,  554 

—  strophantin.  528 

—  uric  acid,  419 
Ptomaines,  498 
Ptomatines,  498 
Ptyalin,  570 
Puddling  process.  281 
Pumice  stone.  248 
Purin,  415,  551 

—  derivatives,  415 
Purple  ot  Cassius  292 
PurpuieocobaltJc  salts,  286 
Puipunc  acid  415 
Purpurin   517 
Putrefaction  325 

—  bases.  398 
Putrescin,  398 
Py  rami  don.  551 
Pyrargynte,  170,  181- 
Pyrazine,  542 
Pyrazole  550 
Pyrazoiidine,  550 
Pyrazoline,  550 
Pyrazoiin  ketone,  551 


INDEX. 


615 


Pyrazolon,  551 
Pyrene,  513 
Pyridazine,  542 
Pyridine,  538 

—  bases,  538 

Pyridine  carbonic  acids,  538 
Pyridy}-,  554 
Pyrimidine,  542 
Pyrites,  277 
Pyro-,  319 

Pyroantimonic  acid,  180 
Pyroarsenic  acid,  175 
Pyroboric  acid,  185 
Pyrocatechin,  480 

—  carbonic  acid,  494 

—  methyl  ether,  480 
Pyrochlore,  265 
Pyrocormane,  541 
Pyrogallic  acid,  482 
Pyrogallol,  482 

—  carbonic  acid,  476 

—  dimethyl  ether,  482 

—  phthalein,  508 
Pyrolusite,  273 
Pyromeconic  acid,  541 
Pyromellitic  acid,  503 
Pyromucic  acid,  549 
Pyrone,  541 

Pyrophosphoric  acid,  169 
Pyroracemic  acid,  403,428 
Pyrosin,  508 
Pyrosulphuric  acid,  124 
Pyrotartaric  acid,  428 
Pyroxylin,  457 
Pyrrodiazole,  551 
Pyrrolidin  carbonic  acid,  545 
Pyrrolidine,  545 
Pyrroline,  545 

Pyrrol,  544 
Pyrrol  groups,  545 

Quadratic,  svstem  of  crystals,  34 

Quartz,  190 " 

Quassin,  529 

Quebracol,  526 

Quellic  acid,  326 

Quercetin,  541 

Quercitrin,  528 

Quercite,  482 

Quicksilver,  242 

Quina  tannic  acid,  496 

Quinaldine,  539 


Quinazoline,  543 
Quinhydrones,  481  ^ 

Quinic  acid,  496 
Quinidine,  555 
Quinine,  555 

—  salts,  555 
Quinoline,  539 

—  bases,  539 

—  dyes,  540 

—  salts,  539 
Quinone,  481 
Quinonaniles,  482 
Quinonchlorimides,  482 
Quinondichlorimides,  482 
Quinonimide,  485 

—  dyes,  485 
Quinonoxaline,  543 
Quinova  tannic  acid,  496 
Quinovic  acid  527 
Quinovin,  527 
Quinovose,  444 
Quinoxonime,  482 

Racemic  acid,  428 

—  modifications,  39 
Radicals,  96,  328,  336 

—  See  also  alcohol  and  acid  radi- 

cals. 

—  of  dicarbonic  acids,  421 

—  of  fatty  acids,  336 

—  of  oxyfatty  acids,  401 

—  primary,  329 

—  secondary,  329 

—  tertiary,  329 
Radio-active  metals,  272 
Radium,  272 
Raffinose,  456 
Rain-water,  116 
Rancidity  of  fats,  435 
Raoult-van't  Hoff 's  law,  19 
Rapinic  acid,  440 
Reaction,  6 

—  acid,  84 

—  alkaline,  85 

—  basic,  85 

—  complete,  61 

—  endothermic,  68 

—  exothermic,  68 

—  inverse,  61 

—  neutral,  85 

—  reversible,  61 

—  velocity,  65 


616 


INDEX. 


Reafi:ents,  6 
Realgar,  1.70 
Rearrangement,  allotropic,  7 

—  isomers,  7 
Red  haematite,  277 
Reductase,  106 
Reduction,  106 

—  flame,  92 

—  zone  of  the  blast-furnace,  280 
Refraction  constant,  38 
Regular  system  of  crystals,  34 
Reimer-Tiemann's  synthesis,  492 
Resenes,  525 

Resin  alcohols.  526 
Resins,  524 
Resin  ester,  525 

—  soaps,  525 

—  varnish,  525 
Resines,  525 
Resinoles,  525 
Resinotannoles,  525 
Resorcin,  481 

—  blue,  481 

—  phthalein,  508 

—  yellow,  510 
Respiration,  109 
Rennin,  571 
Retene,  518 
Retinol,  523 
Retort  graphite,  187 
Rhamnazin,  542 
Rhamnegenin,  529 
Rhamnetin,  542 
Rhamnin,  529 
Rhamnite,  443 
Rhamnochrysin,  541 
Rhamnocitrin,  541 
Rhamnolutin,  542 
Rhamnose,  444 
Rhamnosides,  526 
Rhein,  517 

Rheum  tannic  acid,  496 

Rhodamin,  294 

Rhodinol,  444 

Rhodium,  294 

Rhodochrosite,  273 

Rhodophan,  532 

Rhombic,  system  of  crystals,  34 

Rhusma,  220 

Ribonic  acid,  444 

Ribose,  444 

Ricin,  572 


Ricinelaidic  acid,  441 
Ricinoleic  acid,  441 

—  sulphuric  acid,  441 
Rinmann's  green,  232 
Robin,  572 
Roborin,  562 
Roccellic  acid,  420 
Rock  crystal,  195 

—  oil,  341 

—  salt,  210 
Rodmal,  480 
Rodophan,  532 
Rochelle  salts,  429 
Roll  sulphur,  120 
Rosaniline,  506 
Rose  bengal,  508 
Rosemary-oil,  521 
Rose's  metal,  264 
Roseocobaltic  salts,  286 
Rose-oil,  521 

Rose  quartz,  195 
Rosindulines,  543 
Rosolic  acid,  508 
Rotation,  specific,  40 

—  optical,  39 

—  degree,  40 

—  of  the  C  atoms,  305 
Rottlerin,  532 
Ruberythric  acid,  528 
Rubidium,  215 
Rubijervine,  559 
Ruby,  249 

Rum,  355 
Rust,  278 
Ruthenium,  294 
Rutile,  262 

s=  symmetrical,  469 
Sabadin,  559 
Sabadinin,  559 
Sabinole,  524 
Saccharic  acid,  446 
Saccharides,  448,  526 
Saccharin,  489 
Saccharonic  acids,  444 
Saccharose,  453,  489 
Saccharum,  448 
Safety-lamp,  Davy's,  110 
Safflorite,  285 
Safranin  blue.  543 
Safrol.  500 
Safrosin,  508 


INDEX. 


617 


Sago,  459 
Sal-ammoniac,  148 
Salicin,  528 
Salicylates,  492 
Salicylic  acid,  492 

methyl  ester,  492 

amidophenylacetylester,  492 

phenylester,  492 

Salicyl  alcohol,  491 

—  aldehyde,  491 
Salicyluric  acid,  490 
Saligenin,  491 
Salipyrine,  551 
Salkowski's  reaction,  526 
Salmine,  561 

Salocoll,  485 
Salol,  492 
Salophene,  492 
Salt  formers,  132 

—  gardens,  210 

• —  of  sorrel,  423 
Saltpeter,  206 

—  cubical,  212 

—  destroyers,  161 

—  plantations,  206 
Salterns,  210 
Salts,  85,  99,  345 

—  acid,  101 

—  basic,  101 

—  complex,  102 

—  double,  102 

—  neutral,  100 

—  normal,  100 

—  primary,  101 

—  secondary,  101 

—  tertiary,  101 
Salt  solutions,  51 
Salves,  437 
Samandrine,  398 
Samarskite,  248 
Samarium,  247 
Sanatogen,  562 
Sanatol,  521 
Sand,  195 

Sandal  wood-oil,  521 
Sandmeyer's  reaction,  512 
Sandstone,  195 
Santalene,  522 
Santalin,  542 
gantonic  acid,  515 
Santonin,  515 
gantoninic  acid,  515 


Sapocarbol,  491 

Sapogenin,  529 

Saponification,  357,  436 

Saponines,  528 

Sapotoxin,  529 

Sapphire,  249 

Saprine,  398 

Saprol,  491 

Sarcine,  415 

Sarcosin,  369 

Sarcolactic  acid,  407 

Sarsasaponin,  528 

Sassolite,  184 

Sausage  poison,  398 

Savine-oil,  521 

Saxony  blue  dyeing,  549 

Scandium,  247 

Scheele's  green,  237 

Scheelite,  271 

Scheibler's  reagent,  271 

Schlippe's  salt,  212 

Schonite,  228 

Schotten-Raumann's  reaction,  489 

Schreiner's  bases,  543 

Schweinfurter  green,  364 

Schweitzer's  reagent,  236 

Scillain,  529 

Scillitoxin,  529 

Scoparine,  542 

Scopolamine,  558 

Sea-salt,  210 

Sea-water,  117 

Sebacic  acid,  420 

Secondary,  329 

Selenious  acid,  131 

Selenite,  222 

Selenium,  131 

—  dioxide,  131 
Seminin,  453 
Seminose,  453 
Senar-monite,  177 
Septicines,  398 
Seralbumin,  563 
Serglobulin,  564 
Sericin,  569 

Seres,  homologous,  299 
Serin,  407 
Serpentine,  227 
Sesame-oil,  436 

—  reaction  for,  549 
Sesquioxides,  97 
Sesquiterpens,  522 


618 


INDEX. 


Shellac,  525 
Side-isomers,  468 
Sidonal,  496 

Siemen-Martin's  process,  281 
Sienna  earth,  253 
Silicates,  197 
Siliceous  sinter,  196 
Silicic  acids,  196 
detection  of,  197 

—  acid  solution  196 

—  anhydride,  195 
Silicidos,  194 

Silicium.     See  Silicon,  193 
Silico  fluorides,  195 
Silicon-bronze,  235 

—  carbide,  194 

—  chloride,  194 

—  chloroform,  194 

—  dioxide,  195 

—  ethyl,  381 

—  fluoride,  194 

—  hydride,  194 

—  sulphide,  195 

—  telluride,  131 
Silicononane,  381 
Silicononyl  acetate,  381 

—  alcohol,  381 

—  chloride,  381 
Silver,  238 

—  alloys,  240 

—  alum,  252 

—  amalgam,  238 

—  amide,  241 

—  arsenate,  175 

—  arsenite,  174 

—  bromide,  240 

—  carbonate,  240 

—  chloride,  240 

—  chromate,  271 

—  citrate,  431 

—  compounds,  240 

—  coins,  240 

—  cyanide,  386 

—  detection  of,  24 1 

—  extraction  of,  238 

—  foil,  239 

—  fulminate,  390 

—  glance,  238 

—  group,  233 

—  hydroxide,  240 

—  hydrazoate,  151,  241 
^  iodide,  241 


Silver  mirror,  350 

—  nitrate,  241 

—  nitrite,  241 

—  oxide,  240 

—  peroxide,  240 

—  phosphate,  169,  170 

—  subchloride,  240 

—  sulphide,  240 

—  theobromine,  418 
Silvestren,  522 
Sinapic  acid,  501 
Sinapine,  559 
Sincalin,  379 
Sinigrin,  438 
Sitosterin,  526 
Skatol,  548 

Skatoxy]  sulphuric  acid,  548 

Skraup's  synthesis,  540 

Slag,  280 

Slaking  of  lime,  220 

SHbowitz,  355 

Smilacin,  528 

Smilosaponin,  528 

Smithsonite,  230 

Smoky  topaz,  195 

Snail  mucin,  566 

Snake  poison,  572 

Snow-water,  116 

Soaps,  436 

Soap  plaster,  437 

—  spirits,  437 
Soapstone,  227 
Soda,  213 

—  lime,  311 
Sodium,  209 

—  acetate,  363 

—  aceto-acetic  ester,  366 

—  acetylene,  442 

—  alum,  252 

—  amalgam,  243 

—  ammonium  hydrophosphate,  217 

—  aluminium  fluoride,  248 

—  bicarbonate,  215 

—  bisulphite,  210 

—  borneol,  523 
-^  bromide,  210 

—  camphor,  523 

—  carbonate,  normal,  213 
primary  or  acid,  215 

—  chloride,  210 

—  chloroaurate,  291 

—  chromate,  269 


INDEX. 


619 


Sodifim,  detection  of,  215 

—  dichromate,  270 

—  ethyl,  382 

—  ethylate,  355 

—  glycol,  401 

—  hydrazoate,  151 

—  hydride,  209 

—  hypochlorite,  210 

—  hyposulphite,  211 

—  hydroxide,  209 

—  iodide,  210 

—  metaplumbate,  262 

—  nitrate,  212 

—  oxides,  209 

—  peroxide,  107,  209 
' —  persulphide,  124 

—  phenylate,  474 

—  phosphate,  primary,  212 
secondary,  212 

tertiary,  212 

—  plumbate,  262 

—  potassium  tartrate,  429 

—  pyroantimonate,  180 

—  pyrophosphate,  169 
— -  salicylate,  492 

—  saltpeter,  212 

—  silicate,  215 

—  soap,  437 

—  stannate,  257 

—  sulphate,  211 

—  sulphides,  122,  209 

—  sulphite,  210 

—  sulphoantimonate,  212 

—  sulphocarbonate,  193 

—  sulphocyanide,  393 

—  tetraborate,  212 

—  thiocyanate,  393 

—  thiosulphate,  211 

—  tetrathionate,  311 

—  tungstate,  271 

—  water-glass,  215 
Soft  resins,  525 
Soffioni,  184 
Solanidine,  559 
Solanine,  559 
Soles,  54 
Solidification  point,  35,  37 

—  heat  of,  36 
Solutions,  46 

—  colloidal,  54 

—  equimolecular,  19 

—  heat  of,  68 


Solutions,  supersaturated,  52 
Solution  electrodes,  90 

—  pressure,  51,  88 
electrolytic,  88 

—  saturated,  51 

—  tension,  88 

Solvay's  soda  manufacture,  214 

Solveol,  491 

Somatose,  562 

Sonnenschein's  reagent,  271 

Sorbin,  453 

Sorbinose,  453 

Sorbinic  acid,  445 

Sorbite,  446 

Sorbose,  453 

Soson,  562 

Sozoiodolic  acid,  480 

Sozolic  acid,  480 

Space  isomerism,  303 

Spathic  iron  ore,  277 

Specific  gravity,  36,  38,  43 

of  the  metals,  198 

Speculum  metal,  235 
Spectra,  44 
Spectral  analysis,  44 
Spectroscope,  45 
Spermaceti,  375 
Spermin,  543 
Spiegeleisen,  273 
Spinel,  251 
Spirit  blue,  507 
Spirits  of  wine,  353 
Spongin,  569 
Stachyose,  456 
Stalactites,  224 
Stannates,  257 
Stannic  acids,  257 

—  anhydride,  257 

—  chloride,  257 

—  compounds,  257 

—  hydroxide,  257 

—  oxide,  257 

—  sulphide,  257 
Stannous  chloride,  256  ^ 

—  compounds,  256 

—  hydroxide,  256 

—  oxide,  256 

—  sulphide,  257 
Stannum,  255 
Starch,  458 

—  animal,  459 

—  cellulose,  458 


620 


INDEX. 


Starch  granulose,  458 

—  gum,  459 

—  paste,  458 

—  soluble,  459 

—  sulphuric  acid,  459 

—  sugar,  451 
Stassfurt  salts,  202 
Statics,  chemical,  60 
Stearic  acid,  277 
Stearin,  277,  435 

—  candles,  277 
Stearoptene,  521 
Steapsin,  571 
Steel,  278,  281 
Stercorine,  526 
Stephanite,  238 
Stereochemistry,  302 
Stereoisomerism,  302 
Stereotype,  264 
Stibines,  377,  380 
Stibium,  177 
Stibonium  bases,  380 
Stibnite,  177 
Stilbene,  508 
Stoichiometry,  3,  5 
Stolzite,  271 
Stoneware,  253 
Storax,  525 

Strass  or  paste,  224 

Stromeyerite,  238 

Stronium    method    of    extracting 

sugar,  454 
Strontianite,  225 
Strontium,  225 

—  compounds,  225 

—  detection  of,  225 

—  hydroxide,  225 

—  oxide,  225 

—  saccharate,  454 

—  salts,  225 

—  sulphide,  220 
Strophantin,  528 
Structure,  chemical,  29 

—  organized,  4 

—  of  flame,  92 

—  of  organic  compounds,  296 

—  —    —    —    determination     of, 
317 

Structures,  60 
Structural  formulae,  30 
Strychnine,  554 
Stypticine,  556 


Styphnic  acid,  481 
Styracin,  501 
Styrene,  498 
Sturin,  561 
Suberic  acid,  420 
SubUmate,  245 
Sublimation,  36 

—  pressure,  36 
Suboxides,  97 

Substance,  fibrino-plastic,  564 

—  incnisting,  458 

—  gelatine-forming,  569 
Substitution,  6,  31,  299,  464 

—  in  the  benzene  nucleus,  467 

—  in  the  side  chain,  468 

—  weights,  31 
Succinic  acid,  424 

—  anhydride,  424 

—  acid  imide,  420 
Succinates,  424 
Succinimide,  420 
Succinyl,  421 
Sucrase,  570 
Sucrol,  4S0 
Sugars,  447 
Sugar  color,  454 
Sugar  of  lead,  363 
Sulphanilic  acid,  484 
Sulphamin-benzoic  acid,  489 
Sulphates,  130 
Sulphides,  96 

—  detection  of,  123 

—  of  the  heavy  metals,  123 
Sulphines,  352 
Sulphinic  acids,  401 
Sulphin  bases,  352 

—  oxides,  352 
Sulphites,  126,  401 
Sulphmethyl.  329 
Sulpho  acids,  98,  401 

of  antimony,  181 

of  arsenic,  176 

Sulphoantimonic  acid,  181 
Sulphoantimonous  acid,  181 
Sulphoarsenic  acid,  178 
Sulphoarsenious  acid,  178 
Sulphoauric  acid,  292 
Sulphocarbamide,  411 
Sulphocarbonates,  193 
Sulphocarbonic  acid,  192 
Sulphocarbonyldisulphocarbonic 

acid,  408 


INDEX. 


621 


Sulphocyanic  acids,  393 

—  acid  compounds,  393 
Sulphogermanic  acid,  258 
Sulphonal,  372 
Sulphones,  352 
Sulphonic  acids,  401 
Sulphonium  oxide,  352 
Sulphoplatinic  acids,  293 
Sulpho-salts,  176,  181 
Sulphostannate,  257 
Sulphoxides,  352 
Sulphur,  119 

—  amorphous,  121 

—  detection  of,  121 

—  dichloride,  139 

—  dioxide,  124 

—  dyes,  552 

—  estimation     in     organic     com- 

pounds, 310,  312 

—  ethers,  332 

—  heptoxide,  131 

—  monochloride,  139 

—  monoelinic,  120 

—  oxides  and  oxyacids,  124 

—  plastic,  121 

—  regeneration  of,  213 

—  rhombic,  121 

—  selenide,  131 

—  sesquioxide,  131 

—  trioxide,  126 

—  tetraoxide,  139 

—  waters,  117 
Sulphuric  acid,  127 
ethyl  ester,  357 

—  anhydride,  126 

anhydrous,  129 

dilute,  129 

detection  of,  130 

crude,  129 

fuming,  129 

pure,  129 

Sulphuric  ether,  358 
Sulphurous  acid,  126 
detection  of,  126 

—  anhydride,  124 
Sulphuretted  hydrogen,  122 
detection  of,  123 

reagent  and  precipitant,  123 

Supercooling,  35 
Superfusing,  35 
Superheating,  37 
Superphosphate.  223 


Superoxides,  97 
Sycose,  489 
Syenite,  195 
Sylvestrene,  552 
Sylvine,  202,  204 
Symbols,  chemical,  25 
Syn-forms,  309 
Synaptase,  571 
Synbenzaldoxin,  309 
Synthesis  of  water,  112 
Synthetical  chemistry,  2 
Synthetic  study  of  molecular  for- 
mulae, 318 
Syntonin,  568 
System,  60 

—  variant,  64 

—  of  crystals,  34 

Table  of  the  chemical  elements,  25 

—  of  symbols  and  atomic  weights, 

25 
Talc,  227 
Tallow,  436 
Talmi-gold,  235 
Tanaceton,  524 
Tannic  acid,  495 
Tannigen,  495 
Tannin,  495 
Tanning  bodies,  495 
Tannoform,  350 
Tannogens,  496 
Tannoids,  496 
Tantalum,  265 
Tantalite,  265 
Tapioca,  459 
Tar,  341 

—  asphalt,  324 

—  benzine,  478 

—  colors,  531 
Tartar.  429 

—  emetic,  430 
Tartrates,  429 
Tartaric  acid,  427 
inactive,  428 

—  anhydride,  428 
Tartrelic  acid,  428 
Tartronic  acid,  434 
Tartronyl  urea,  414 
Taurin,  401 
Taurocholic  acid,  401 
Tautomerism,  300,  365 
Tea  tannic  acid,  496 


622 


INDEX. 


Teichmaim's  blood-crystals,  545 
Tellurium,  131 

—  dioxide,  132 
Temperature,  critical,  41 

—  of  flames,  93 
Tempering  of  steel,  279 
Tennanite,  170 
Tension,  40,  49,  115 

—  chemical,  7 
Terra-cotta,  253 
Terbium,  247 
Terebene,  522 
Terebentene,  522 
Terpentine,  522 

—  oil,  522 

Terephthalic  acid,  497 
Terpane  structure,  519 
Terpanes,  522 
Terpenes,  503,  519 

—  olefines,  519 
Terpine,  524 
Terpinen,  522 
Terpineol,  524 
Terpinols,  522 
Terpin  hydrate,  524 
Tertiary,  329 
Tetanin,  398 
Tetatoxin,  398 
Tetraboric  acid,  185 
Tetrabromfluorescein,  508 
Tetrachlorquinone_,  482 
Tetrachlormethane,  348 
Tetradecylalcohol,  342 
Tetradyrnite,  131 
Tetraethylammonium  iodide,  379 
Tetragonal  system  of  crystals,  34 
Tetrahedrite,  233 
Tetrahydropyrazole,  550 
Tetrahydro-oxazine,  544 
Tetrahydropyrrol,  545 
Tetrahedral  form  of   the  C  atom, 

304 
Tetraiodophenolphthalein,  508 
Tetraiodopyrrol,  545 
TetraiodofluoresceTn,  508 
Tetramethylendiamine,  398 
Tetramethyl  alloxanthine,  415 

—  ammonium  hydroxide,  379 

—  arsonium  compounds,  381 

—  benzenes,  502 

—  diamidobenzophenon,  505 

—  diamidodiphenyl  methane,  505 


Tetramethyl  diamidodiphenyl  meth- 
ane, detection  of  ozone  with, 
112 

—  phenylammonium  hydroxide,  384 

—  phosphonium  hydroxide,  380 

—  pyridine,  538 

—  stibonium  hydroxide,  381 

—  uric  acid,  419 
Tetramethylene,  464 
Tetramines,  330 

•  Tetraoxybenzenes,  474,  482 
Tetraphenyl  ethylene,  509 
Tetrasilicates,  197 
Tetrasilicic  acid,  197 
Tetrathionic  acid,  124 
Tetrazines,  543 
Tetrazo  compounds,  510 
Tetrazole  compounds,  551 
Tetrol,  549 

—  group,  544 
Tetrolic  acid,  445 
Tetronal,  372 
Tetroses,  447 
Thallium,  254 

—  sulphide,  255 
Thebaine,  556 
Theine,  418 
Thenard's  blue,  254 
Theobromine,  418 

—  sodium  salicylate,  418 
Theobromic  acid,  377 
TheophylUne,  416 
Thermite,  249 
Thermochemistry,  67 

Theory    of   atoms  and    molecules, 
13 

—  of  Arrhenius,  77 

—  kinetic,  40 

—  of  electrolytic  dissociation,  77 

—  of  ions,  77 

—  of  Le  Bel-van't  Hoff,  304 

—  of  periodicity,  55 

—  of  valence,  27 

—  of  van  der  Waals,  42 

—  of  van't  Hoff,  19 
Thiacetic  acid,  368 
Thiamides,  336 
Thiazine  compounds,  544 

—  dyes,  544 
Thiazole,  552 

—  dyes,  552 
Thiazole.  yellow,  552 


INDEX. 


623 


Thilanin,  526 

Thioacetic  acid,  368 

Thio  acids,  335 

Thio  alcohols,  332 

Thioantimonic  acid,  181 

Thioantimonous  acid,  181 

Thioarsenious  acid,  176 

Thioarsenic  acid,  176 

Thiocol,  481 

Thiocyanic  compounds,  393 

Thiocyanate  compounds,  393 

Thiodiphenylamine,  544 

Thio  ether,  332 

Thioflavin,  552 

Thioform,  493 

Thiolic  acids,  339 

Thiols,  332 

Thiomonazole,  552 

Thionic  acids,  339 

Thionaphthene,  550 
Thionin  dyes,  544 
Thiophtene,  550 
Thiophene,  550 
Thiophenic  acid,  550 
Thiophenol,  480 
Thiotolene,  550 
Thiosinamine,  411 
Thiosulphuric  acid,  124 
Thiourea,  411 
Thioxene,  550 

Thomas-Gilchrist  process,  281 
Thomas  phosphate,  281 
—  slag,  223 
Thoria,  263 
Thorite,  263 
Thorium,  263 
Thorium  oxide,  263 
Thrombase,  571 
Thrombin,  571 
Thujone,  524 
Thulium,  247 
Thyme-oil,  521 
Thyme  camphor,  503 
Thymin,  565 
Thyminanic  acid,  503 
Thymic  acid,  565 
Thymol,  503 

Thymohydroquinone.  474 
Thymus  nucleic  acid,  565 
Thyphotoxin,  398 
Thyreoiodin,  565 
Thyroglobin,  565 


Tiemann's  synthesis,  492 
Tin,  255 

—  alkyls,  382 

—  alloys,  256 

—  amalgam,  243 

—  ash,  255 

—  compounds,  256 

—  chloride,  257 

—  detection  of,  258 

—  foil,  256 

—  group,  255 

—  hydroxide,  256 

—  oxide,  257 

—  oxy chloride,  257 

—  protochloride,  256 

—  salt,  257 

—  stone,  255 

—  sub-oxide,  256 

—  sulphides,  257 

—  zinc  amalgam,  243 
Tiger  eyes,  195 
Tiglic  acid,  440 
Tinctures,  355 
Tincture  of  iodine,  142 
Tinkal,  183 
Titanium,  262 
Tolane,  509 
Toluylene  blue,  543 

—  red,  543 

—  alcohols,  497 
Tolu  balsm,  525 
Toluene  compounds,  486 

—  chlorides,  487 

—  phenols,  491 
Toluic  acids,  497 
Toluric  acid,  490 
Toluidine  blue,  544 
Toluidines,  487 
Toluic  aldehyde,  497 
Toly]  alcohol,  497 
Toluyl  compounds,  487 
Tolylene,  508  _ 
Tolvloxy butyric  acid,  503 
Topaz,  248 

Tormentilla  tannic  acid,  496 
Tourmalin,  248 

Toxins,  398 
Toxalbumines,  571 
Toxomucoid,  567 
Tragacanth,  4(J0 

Transition  of  the  cyclic  into  the  ali- 
phatic compounds,  470 


624 


INDEX. 


Transition  of  the  isGcyclic  and  ali- 
phatic compounds  to  the  hetero- 
cyclic compounds,  534 

Transport  of  electricity,  81 

Trans-form,  308 

Transformations,  chemical,  6 

—  multiple,  7 

Trehalase,  570 

Trehalose,  455 

Triacetin,  432 

Triamines,  330 

Triamidobenzene,  483 

Triamidodiphenyltolyl  carbinol,  506 

Triamidotriphenyl  carbinol,  506 

Triazine  compounds,  543 

Triazoiodide,  152 

Triazole  compounds,  551 

Tribenzodiazine,  543 

Tribrommethane,  548 

Tribromphenol,  479 

Tricarballylic  acid,  431 

Trichloracetic  acid,  368 

Trichloraldehyde,  360 

Trichlorlactic  acid  amide,  418 

Trichlormethane,  347 

Trichlorpurin,  419 

Trichromic  acid,  269 

Triclinic  system  of  crystals,  35 

Tridymite,  195 

Triethylamine,  378 

Triethylendiamine,  397 

Triethylin,  434 

Triethyl  benzenes,  472 

Trigonelline,  553 

Trihydrocyanic  acid,  385 

Tri-iodomethane,  347 

TrimeUitic  acid,  499 

Trimesic  acid,  499 

Trimethylamine,  379 

Trimethylarsine,  380 

Trimethyl  arsine  oxide,  380 

Irimethyl  benzene  compounds,  499 

Trimethyl  phosphonium  c  o  m- 
pounds,  380 

Trimethyl  pyridine,  538 

Trimethylvinylammonium  hydrox- 
ide, 380,  438 

Trimethylxanthine,  418 

Trimethylene,  464 

Trimethylenimine,  397 

Trimethyloxyethyl  ammonium  hy- 
droxide, 379 


Trimorphism,  35 
Trinitronaphthalene,  514 
Trinitrobutyltoluene,  503 
Trinitroresorcin,  481 
Trinitrophenol,  479 
Trional,  372 
Trioxy  acrylic  acid,  415 

—  anthraquinones,  517 

—  benzaldehyde,  494 

—  benzenes,  482 

—  benzoic  acids,  494 

—  benzyl  alcohol,  494 

—  butyric  acid,  443 

—  cinnamic  acid,  501 

—  glutaric  acid,  444 

—  methylene,  350 

—  purin,  416 

—  toluenes,  494 

—  triphenyl  carbinol,  507 
Triolein,  435 

Trioses,  447 

Tripalmitin,  435 

TripoUte,  195 

Triphenylamine,  484 

Triphenylcarbinol,  506 

Triphenylethylene,  509 

Triphenylmethane  derivatives,  505 

Triphenylrosaniline,  507 

Triphylite,  215 

Trisaccharides,  456 

Trisihcates,  197 

Tirsilicic  acid,  197 

Trisulphocarbonic  acid,  408 

Trisubstitution  products,  469 

Tristearin,  435 

Trisazo  dyes,  510 

Trithionic  acid,  124 

Tropacocaine,  558 

Tropaeolins,  510 

Tropeines,  557 

Tropine,  557 

Tropine  carbonic  acid,  558 

Tropon,  562 

Tropanol,  557 

Tropic  acid,  502 

True  blue,  510 

—  red,  510 

—  yellow,  510 
Truxilic  acid,  501 
Trypsin,  570 
Tryptophan,  561 
Tuberculin,  572 


INDEX, 


625 


Tuberculocidin,  572 
Tungstates,  271 
Tungstic  acid,  271 
Tungsten,  271 

—  bronze,  271 

—  steel,  271 

—  trioxide,  271 
Turkey-red,  517 

—  oil,  441 

Turmeric  paper,  531 
Turnbull's  blue,  389 
Type  metal,  178 
Typhotoxin,  398 
Tyrosin,  502 
Tyrosinase,  571 

Ulmin,  326 

Ulminic  acid,  326 

Ultramarine,  253 

Umbellic  acid,  501 

Umbelliferone,  501 

Undecane,  340 

Unsymmetry  of  the  C  atoms,  39 

Ur-acids,  413 

Uracil,  542 

Uramil,  419 

Uranates,  272 

Uranite,  192 

Uranium,  272 

—  compounds,  272 

—  oxide,  272 

—  pitchblende,  272 

—  rays,  272 

—  yellow,  272 
Uranyl,  272 

—  chloride,  272 

—  nitrate,  272 

—  oxide,  272 

—  phosphate,  272 

—  sulphate,  272 

—  sulphide,  272 
Uranylic  acid,  272 
Urari,  554 
Urates,  419 
Urea,  409 

—  derivatives,  411,  413 

—  nitrate,  411 

—  oxalate,  411 
Ureas,  alkylated,  413 

—  compound,  413 
Ureides,  413 
Urethan,  409 


Uric  acid,  418 
Urobilin,  546 
Urobilinogen,  546 
Urol,  496 
Urosin,  496 
Urotropin,  398 
Urson,  529 
Usninic  acid,  497 
Uvitic  acid,  499 

v=,469 

Valence  theory,  27 

—  of  acids  and  bases,  98, 100 

—  of  the  elements,  27 
Valentinite,  180 
Valerianic  acid,  374 
Valeric  acid,  374 
Valerylene,  441 
Validol,  524 
Vanadinite,  265 
Vanadium,  265 

Van  der  Waal's  theory,  42 
Van't  Hoff's  theory,  19,  304 
VaniUin,  494 
Vapor,  40 

—  abnormal,  72 

—  density,  16,  43 

determination  of,  314,  315 

—  pressure,  40 

—  tension,  40 

—  of  water,  154 

—  saturated,  115 

—  supercooled,  41 

—  volume  relationship,  42 
Vaporization,  heat  of,  33,  35,  36 
Varec,  142 

Vaseline,  342 

—  oil,  342 
Vasogene,  342 
Vasol,  342 
Ventian  white,  226 
Veratric,  494 
Veratrine,  559 
Veratrol,  481 
Verdigris,  234,  364 
Vermillion,  245 
Vesuvin,  510 
Vicilin,  565 
Victoria  blue,  515 
Vidal's  black,  552 
Vinegar,  362 

—  essence,  362 


626 


INDEX. 


Vinegar,  fungi,  362 
Vinyl,  437 

—  alcohol,  437 

—  chloride,  397 

—  sulphide,  437 
Vioform,  540 
Violuric  acid,  419 
Vitellins,  565 
Vitrification,  195 
Vitriol  blue,  236 

—  green,  282 

—  white,  232 
Vivianite,  283 
Volemite,  447 
Volemose,  447 
Voltometer,  76 
Volume  compounds,  11 

— relationships  in  chemical  changes, 
12 

—  critical,  41 

—  specific,  43 

—  weight,  43 
Vulcanite,  523 
Vulcanization,  523 

Water,  112 

—  analysis,  104 

—  of  constitution,  115 

—  of  crystaUization,  115 

—  distilled,  113 

—  gas,  189 

—  glass,  215 

—  hard,  116 

—  mortar,  220 

—  natural,  116 

—  river,  116 

—  soft,  116 

—  synthesis,  113 

—  temporary  hardness  of,  116 
Water  blue,  507 

Wall  saltpeter,  206 
WaveUite,  162 
Wax,  375 

Weight  and  volume  relationship  in 
chemical  changes,  12 

—  of  the  atoms  and  molecules,  14, 

21 
Weldon's  process,  274 
Welsbach  light,  92 
Well-water,  117 
Whale  blubber,  375 
Wheat-starch,  459 


White  lead,  261 
Wine,  356 

—  brandy,  355 

—  oil,  376 
Will-Varrentrapp's  nitrogen  estimap 

tion,  311 
Websterite,  251 
WiUemite,  230 
Witherite,  226 
Wohlerite,  265 
Wolfram,  271 
Wolframite,  271 
Wolframic  acid,  271 
Wollastonite,  224 
Wood,  dry  distillation  i)f,  324 

—  alcohol,  349 

—  charcoal,  187 

—  gum,  444 

—  sugar,  444 

—  tar,  324 

—  vinegar,  362 
Wood's  metal,  264 
Wool  fat,  526 

Work  of  the  electric  current,  82 
Wormwood  camphor,  524 
Wort  of  beer,  356 
Wrought  iron,  279 
Wulfenite,  271 

Xanthine,  417 

—  bases,  415 
Xanthocarotin,  532 
Xanthogenic  acid,  408 
Xanthon,  541 
Xanthophan,  532 
Xanthophyll,  532 
Xanthoproteic  reaction,  562 
Xanthorhamin,  529 
Xenon,  182 

Xereform,  479 
Xylan,  444 
Xylenes,  496 
Xylene  phenols,  496 
Xylenoles,  496 
Xyhc  acids,  499 
Xylidic  acid,  499 
Xylite,  443 
Xylogen,  458 
Xylohydroquinone,  496 
Xyloidin,  459 
Xylonic  acid,  444 
Xylorcin,  496 


INDEX. 


627 


Xylose,  444 

Yellow  wash,  245 
Yohimbenin,  559 
Yohimbim,  559 
Ytterbium,  247 
Yttrium,  247 
Yttrotantolite,  248 

Zapon  varnish  or  lacquer,  458 

Zeolites,  248 

Ziiic,'230 

—  acetate,  364 

—  alcoholates,  382 

—  alkyls,  382 

—  alloys,  231 

—  aluminate,  251 

—  blende,  230 


Zinc  carbonate,  232 

—  chloride,  231 

—  comj^ounds,  231 

—  detection  of,  232 

—  ethyl,  382 

—  hydroxide,  231 

—  lactate,  406 

—  oxide,  231 

—  phenolsulphonate,  480 

—  powder,  231 

—  spar,  230 

—  sulphate,  232 

—  sulphide,  232 

—  white,  232 
Zincolith,  232 
Zinc-tin  amalgam,  243 
Zircon  light,  203 
Zirconium,  263 
Zymase,  571 


^nold,  c. 


48613 


